Roger Sanders' Waste Oil Heater
After five years of use, much experimentation, many upgrades, and
hundreds of letters from readers and builders, Roger Sanders has
updated his original waste oil heater project with a great deal of new
information and options. What follows is a revision of the original
article that has far more detail and information based on practical
Problem 1: Cleaning.......................................................................2
Problem 2: Low-heat operation....................................................8
Problem 3: Oil-flow stability.........................................................9
Theory of operation......................................................................13
Practical points of operation.......................................................14
- The flue........................................................................................14
- Air tube restrictor ........................................................................15
- Lighting the burner.......................................................................16
Burning vegetable oil....................................................................24
- Improved starting system.............................................................26
Hot water and home heating.......................................................30
Wood stove conversions...............................................................32
Heating a greenhouse...................................................................33
- Online links..................................................................................35
I built a Mother Earth News Waste Oil Heater (MEN heater) to heat my repair and machine shop,
where the heater gets used all day, every day, for about eight months of the year. The MEN heater
works as claimed and puts out a lot of heat. I was pleased to find that I could successfully use waste
oil to heat my shop.
However, after using the MEN heater for several months, I became so
frustrated with its problems that I concluded that it is unsuitable for
serious, regular use. So I embarked on a journey to design and build a
more practical heater.
There are three big problems with the MEN heater. These are:
2) Low-heat operation
3) Oil-flow stability
Problem 1: Cleaning
Cleaning the MEN heater is a major hassle. Burning waste motor oil
leaves deposits in the combustion chamber. Calling these deposits
"ash" is deceiving as they can be as hard as concrete and just as hard
Experience reveals that there are actually several different types of
deposits. These can be broken down into two basic types that I'll call MEN heater built by
"ash" and "coal." Journey to Forever
"Coal" deposits are dark gray (almost black) and appear much like unburned charcoal. These
deposits are very hard and must be chipped away from the burner surfaces using a hammer or cold
chisel and hammer. They form on the hot metal surfaces inside the combustion chamber where the
oil changes state from a liquid to a gas (vaporization).
"Ash" deposits are crusty, light, airy, and are easy to wipe away with a gloved hand or putty knife.
They mostly are light in color, ranging from tan to light gray, although
some are black. For easy cleaning, "coal" must be avoided at all costs,
only "ash" must remain to be removed.
Vaporization heaters (like the MEN heater) must be cleaned every few
hours of operation, depending on the oil used, the contaminants
present, and how hard you run the heater. If you use your heater every
day, all day, this means that you'll have to clean your heater every
morning before you light it for the day.
This cleaning ritual is a serious problem with the MEN heater due to
its complicated burn chamber. There are many parts and some of them
have rounded surfaces, which make them hard to access for cleaning,
and they are bolted together. The heater produces heavy "coal" Photo #2
deposits. MEN heater burn chamber
The nuts and bolts inside the MEN heater's combustion chamber become encrusted with coal,
making them difficult to unscrew. Once the parts are separated, it is necessary to use a hammer and
chisel to break away the coal.
Its rounded surfaces are hard to clean because a hammer, putty knife, or chisel only contacts a small
area, which forces you to spend a lot of time cleaning small spots, and the parts must be constantly
turned to expose new areas to clean. It is much easier and faster to clean flat surfaces. It is necessary
to use a drill to clear out the holes in the burner. This dirty, messy, time-consuming and frustrating
task gets old very quickly.
Others have tried to deal with this problem, like Bruce Woodford. I tried Bruce's forced-air heater,
which uses a simple combustion chamber filled with loose bolts to make it easier to clean.
This is a simpler design than the original MEN heater, and it is more efficient. It was easier to clean
too. I give Bruce high marks for his design. But there were still problems.
Shaking the bolts as recommended did a fine job of removing the ash,
but the bolts were also coated with coal, and shaking them did not
completely clean them. Eventually you have to beat on them with a
hammer to break the really hard deposits free, and this was time-
consuming and difficult as they are hard to hold and have rounded
An easier solution is to replace the bolts, but large bolts are
expensive. The cylindrical burner also became coated with coal, and
because access to the inside is very limited, cleaning it was difficult. Photo #3
Bruce Woodford's combustion
Another issue was that fishing the loose bolts out of a pile of ash was
a messy business. Setting the bolts back into place in the combustion chamber was a fiddly job that
tried my patience. I didn't like the noise and complexity of using an electric blower. The heater
would not run reliably at low heat settings.
All this frustration finally compelled me to design my own combustion chamber and heater.
Conceptually, vaporization heaters are simple and easy to design. They work by vaporizing liquid
oil upon a hot metal surface. The vapors are flammable, and when mixed with adequate amounts of
air, they burn very well. But making a design that doesn't produce coal is very challenging.
The heart of the problem is that as oil boils and evaporates from the hot vaporization surface, it
leaves behind all the "sludge" from the oil that will not vaporize and burn away. This sludge is
turned into a hard mass by the heat of the burning oil. I found that pure, clean, new, oil has few
deposits, but used crankcase oil is full of contaminants, detergents, and various additives, which
This problem is much like boiling water in a pan or teapot. As the water changes to steam, the
minerals in the water are left behind as "scale" in the pot, forming hard deposits that are difficult to
Commercial waste oil heaters partly solve this problem by atomizing the oil through a nozzle rather
than vaporizing it. The contaminants are atomized as well, so they are not left behind in the nozzle.
A blower is usually used, causing the contaminants to be blown out the flue into the atmosphere.
The contaminants include toxic substances such as heavy metals (including lead, zinc, cadmium and
chromium*) that are better left behind in a burner rather than being discharged into the atmosphere
where we can breathe them. So a vaporization heater is likely to be more "green" than an
atomization heater. My heater is environmentally sound because it distills the oil, automatically
removing heavy metals from the oil before burning it. This heater effectively eliminates airborne,
heavy metal pollution.
Atomizing heaters have other, major problems. They require compressed air or an hydraulic pump
to atomize the oil, the oil must be pre-heated, very well filtered, the nozzles tend to clog with
carbon, low-heat operation is not practical, and the pumps, nozzles, and air compressors add a lot of
complexity and maintenance issues. Also, they use large amounts of electricity, which is expensive
and defeats the idea of using "free" fuel and being environmentally responsible.
I like the simplicity, silence, and economy of a vaporization-type waste oil heater, so I focused my
attention on making one that is extremely simple, noiseless, requires no electricity, that produces
mostly soft ash rather than hard coal, and has only flat surfaces that are easy to clean.
I have designed, built, and tested dozens of burners in trying to develop an ideal combustion
chamber. There isn't the space in this article to describe all the details, changes, and experimentation
involved. So I'll just summarize my findings and describe the burner that solves the problems.
After considerable experimentation, I eventually settled on the idea that the simplest combustion
chamber was best. This took the form of an open "pot" into which the oil would drip, vaporize, and
I tried various types and sizes of pots, with and without different types of internal assemblies. I
found they all could be made to work.
Of course, some worked better than others. I found an 8-inch cast iron pot (20.3 cm) worked quite
well. The nice thing about an open pot is that it is only a single part, does not require any
disassembly, and can simply be lifted out of the stove for cleaning.
But no matter how I made my burn pots, they all produced large amounts of coal deposits that were
hard to clean. But at least they presented a relatively simple surface to clean and there was no
disassembly required, even though they required a hammer and chisel to clean them well. I was not
satisfied, so I continued to search for a better burner.
After more head-scratching and study, I came up with the idea of using a LIQUID vaporization
surface instead of a solid, metal one. I reasoned that vaporizing the oil off a liquid surface would
leave the contaminants behind in the liquid or they would blow off the liquid where they would be
soft and easy to remove. In either case, there would be no hot, solid, metal surface where coal could
form. This insight turned out to be one of the two keys to easy cleaning.
My second insight had to do with the material out of which the burner was made. Usually burners
are made out of cast iron or steel as these will handle a great deal of heat before they melt. But I
found that they are much harder to clean than an aluminum surface. Why would this be?
* See Waste Motor Oil Management May Pose Threat to Health and the Environment, ScienceDaily, Jan. 15, 2004;
Pollution Prevention Impact of Used Oil, Iowa Waste Reduction Center, 2008, quoting the US Environmental
After trying to clean a hot aluminum burner one day, compared to cleaning a cold one, I came to
understand that because aluminum expands and contracts a great deal with temperature, coal
deposits can't stick to it.
If coal is formed on an aluminum burner when it is hot, the coal will break free from the burner as
the burner cools and contracts. Since the coal is very rigid, it just can't stick to an aluminum surface
that is moving and shrinking under it.
But how could I make a liquid vaporization surface? Initially I made a shallow metal cup 4 inches
in diameter (10 cm) and 3/4 of an inch deep (2 cm) into which the dripping oil would pool. The cup
was in the form of a shallow cylinder with a flat bottom. I made it by welding a 1/4-inch thick (6.35
mm) steel plate to a 3/4-inch long section of 4-inch steel pipe. I placed this inside the 8-inch
diameter (20.3 cm) cast iron pot that I had been using as my burner.
I figured that the oil pool in the cup would release vapors into the pot where they would burn. Since
no liquid oil would enter the pot, there would be no coal formed in the pot. But I found that things
worked a bit differently than expected.
The oil dripped into the cup where it boiled and oil vaporized
as expected. But as air flowed over the surface of the oil, it
mixed with the oil vapors, and burst into flame directly over
the top of the oil pool. Photo #4 shows the flames over the oil
pool as seen through the heater's air tube. No oil vapor entered
the pot, no burning occurred within the pot, so the pot was not
even needed. This simplified the design even more.
Initial tests of this cup were promising, as the deposits were
mostly ash and very easy to remove. However, some coal Photo #4
formed on the top edge of the rim of the cup that extended
above the oil pool. Ideally I needed to modify the cup to eliminate this trouble spot.
But there was a much bigger problem, which involved the rate of oil flow. If only a small amount of
oil was dripping into the cup, it vaporized completely and eliminated the oil pool, which resulted in
those dreaded coal deposits. If I ran too much oil into the cup, it overflowed, the oil spilled out into
the pot, and the pot got coated with coal.
In short, it was difficult to find an oil flow that kept the oil
in a liquid pool which didn't overflow the cup. In any case,
there was only one heat level possible and I had no way to
control the heat output.
After more head-scratching, I figured out that what I
needed was a cup whose area increased as the oil flow
increased. The increased oil pool area would make it
possible to vaporize more oil without it overflowing the
I developed a cup that did exactly that. I built a shallow, 5-3/4-inch diameter cup (14.6 cm) whose
interior surface was in the shape of a shallow, inverted cone or funnel of 12 degrees. This also
allowed me to eliminate any lip that could accumulate coal. Photo #5 shows this conical burner.
This conical burner design allowed excellent heat control. When only a little oil was being
introduced into this new burner, it would form a pool about an inch in diameter (2.5 cm) in the
middle of the cone that burned very hot. When a lot of oil was fed into the burner, the oil pool
expanded out to 4 or 5 inches in diameter (10-13 cm), producing much more heat output.
As the burner got hotter from the increased oil flow, the oil would vaporize faster and the pool of oil
shrank down in size to about what it was on low heat. The size of the oil pool was self-regulating
and ensured that there was always a pool of oil present that never overflowed the burner as long as
the oil flow was kept reasonable.
This design allowed me to obtain excellent heat control over a very wide temperature range. I could
get huge amounts of heat or turn it down to where the heater was just barely warm. Since the
burning occurs over the top of the oil pool, the pool is always extremely hot and burns well even at
very low oil flows. It is like using a large combustion chamber for high heat and a small one for low
heat. As a result, the heater burns efficiently and uses a minimum of fuel for any given heat setting.
Because the oil pool does not normally expand to encompass the entire burner, some coal is
produced on the edges of the burner. However, because the burner is aluminum, the coal does not
stick and is easily removed.
I tried several different sized burners. I found that I had to use a large enough burner to handle an
increase in oil flow while allowing the burner to get hot enough to shrink the oil pool back down to
its usual 2-inch size (5 cm). If I used a burner only 2 inches in
diameter, it would overflow anytime I increased the oil flow. If I
used one larger than 6 inches (15.2 cm), the extra area was never
needed. So I settled on a burner that is 5 inches in diameter
I experimented with different tapers on the burner's cone. This
was not critical. But the taper had to be steep enough to hold
enough starting fluid and to prevent overflowing when the oil
flow was increased. I found a 10 to 15-degree angle was
satisfactory. I settled on a 15-degree angle because it held more Photo #6
This burner is incredibly simple and is quick and easy to clean. Cleaning takes only seconds as all
you need do is lift the burner out of the heater and scrape its flat conical surface with a putty knife.
Photo #6 shows the burner after it has been run all day. Photo #7
shows the burner after passing a putty knife over one side. The
ash just falls away without any effort.
Soot is formed in the flue and inside surfaces of all oil heaters.
This soot is self-cleaning on the inside of the heater (but not the
flue pipe), as it gradually flakes off the inside surfaces of the
heater and the flakes fall to the bottom of the heater where you
can easily remove them. Photo #7
You don't have to clean them out often as you can wait until they get several inches deep. With the
MEN heater, you not only have these soot flakes to remove, but you quickly accumulate a lot of ash
from the paper used in the lighting process.
My heater does not use any paper, so has no paper ash. Considerable ash is blown off the conical
burner rather than sticking to it, which is nice because this ash falls to the bottom of the heater
where it mixes with the flakes of soot that fall from the inside of the heater. Photo #8 shows soot
and ash in the bottom of the heater.
I run my heater continuously, so about once a month I
remove the debris. The ash does not adhere to the heater's
surfaces and weighs nothing (much like wood ash), so it is
very easy to remove.
I use a small, hand-held, garden shovel to scoop up the
ashes and put them into a metal bucket. I eventually transfer
them to a normal trash can after I am absolutely sure they
are cold (you don't want a fire in your trash). A vacuum
cleaner works very well, but cleaning a vacuum full of soot Photo #8
and ash is messy, so I prefer using the shovel.
All oil heaters produce some smoke, odor, and a lot of soot. This one is no exception. This is
because oil is a hydrocarbon fuel. It contains long chains of carbon atoms surrounded by hydrogen
atoms. The heater oxidizes the hydrogen, forming water vapor, which is the main exhaust product
from the heater.
The carbon in the oil is not burned. It remains as solid carbon molecules we know as soot. The soot
molecules flow out of the flue with the exhaust gases and you see this as smoke. Generally the
smoke is a bit less than what you would see from a wood stove, but it certainly will be visible.
Photo #9 shows the flue pipe with my
heater running on medium heat, with the oil
flow at about 6 drops per second and a
surface temperature of 500 degrees (260
degrees C). Smoke is visible, but you have
to look carefully to see it. The stove will
smoke more when cold than when hot, just
like a wood stove.
Like a wood stove, the exhaust from an oil
heater has a characteristic odor. In my
opinion, the odor is not offensive. But you
would not want to smell it continuously
(again, just like a wood stove). Normally,
you don't smell any odor. But if the wind is Photo #9
just right, it can pull the smoke down to
ground level where you can smell it. You can usually prevent this by making sure that the top of the
flue is well above the peak of the roof.
Note that soot may seem a dirty pollutant, but this is not necessarily so. Soot molecules are actually
carbon molecules. As such they simply drop out of the air as harmless carbon. If you actually
manage to burn (oxidize) them, you convert them to a gas – either carbon monoxide, a deadly
poison, or carbon dioxide, the well-known greenhouse gas that is now considered an environmental
pollutant. So soot is probably a more benign way to deal with the carbon in oil than burning it.
Even though the soot is only carbon, one should avoid breathing it. It is well proven that breathing
tiny soot particles can cause asthma and lung disease. However, my heater does not produce the tiny
soot particles one finds in diesel engine exhaust fumes. The soot particles from my heater are huge,
so our respiratory system should easily be able to capture and remove them before they reach our
lungs. So even breathing the soot from my heater will probably not cause disease.
In short, I consider my heater to be environmentally friendly and essentially pollution-free.
However, your neighbors may not think so as they see smoke coming from your flue. This could be
a problem in certain locations.
Like a wood stove, you can expect an oil stove to be messy. That is the price you will have to pay to
get free heat from waste oil.
The soot will gradually clog up the flue and you will need to clean it. But the soot is soft and very
easily removed, unlike the creosote formed in a wood stove flue. Also, the soot is non-flammable,
so you have no risk of a flue fire, which is a major concern with a wood stove.
To make cleaning the burner easy, do not put any sand or gravel in the bottom of the heater as is
recommended for the MEN heater. Just leave the bottom of the heater bare steel so you can use the
shovel without picking up any sand.
Problem 2: Low-heat operation
Using an oil pool as a vaporization surface solves the second major problem of the MEN heater, and
that is low-heat operation. The MEN heater produces a lot of heat and requires a rather brisk oil
flow where the oil falls in a steady stream rather than in drops. It has a large vaporization surface
that must be kept hot for efficient operation. This makes it impossible to run the heater at a low heat
setting, which often is needed in mild weather conditions.
By comparison, the flame in a conical oil burner will withdraw to operation only within the center
of the burner where the heat remains intense. This allows the heater to be run on a very low heat
setting as only a slow oil drip (just a couple of drops per second) will still result in excellent flame
stability and efficiency. In other words, the fire stays hot and efficient, but its size is smaller.
When turned down to a low setting, the oil flow can be reduced to only about 2 drops per second,
which is about a teaspoon per minute, or about 5 ml per minute. Such a low flow will burn less than
a gallon of oil per day (3.8 liters). When the heater is running on "high", it can burn about one
gallon per hour, which is about 2 ounces per minute or about 60 ml per minute.
An additional bonus is that lighting this heater is much easier than the MEN heater. You do not need
paper, wood chips, or perlite. You do not need a two-stage lighting process where you light the
paper first to start the draft then light the burner.
All you need to do is fill the burner with kerosene (about 1-1/2 ounces, 44 ml) and light it. Close the
door, turn on the oil to a low setting, and walk away. The heater will establish a draft automatically
as soon as you close the door and the flame will be self-sustaining immediately. After about 20
minutes, you can come back and turn the oil up to a higher setting if you wish.
Photo #10 shows the burner just after being lit. Note
that the flames are going up at this point. But when
you close the door, the draft will start and fresh air will
be drawn down the air tube that is directly over the
burner. This air will force the flames to move
horizontally and extend radially out from the center of
the burner, forming a "flower of flame" that will get
the walls of the heater extremely hot.
Some minor issues have to be addressed when using a
conical oil burner. One is excessive air flow velocity. If
the air comes in too fast, it will blow the vapors off the
pool of oil and the heater can "flame out." Photo #10
You need sufficient air to burn the oil completely, but you have to keep the air velocity low. After
considerable experimentation, I found that you must use a large air tube (a minimum of 4 inches in
diameter, 10 cm), but you must use a restrictor at its inlet to keep the velocity low.
The restrictor I use is just a thin metal plate with a 1-1/2 inch
(3.8 cm) hole in it that sits at the entrance to the air tube. Photo
#11 shows this plate.
This looks professional, but is hard for DIYers to make. An
option that works just as well is a 2 x 4 inch (5 x 10 cm),
rectangular piece of metal that you lay across the intake tube so
that all but an inch (2.5 cm) of the opening is obstructed. Photo Photo #11
#12 shows such a plate.
Note that I do not use an air pipe pre-heater like the MEN stove.
It just isn't needed. My air pipe starts at the top of the heater and
ends 6 inches (15.2 cm) above the burner. It gets very hot from
the fire inside the heater, and since the air flows through the
pipe slowly, the air has adequate time to get hot.
Problem 3: Oil-flow stability Photo #12
Oil-flow stability is a problem with all gravity-fed, waste oil
heaters. This is because the viscosity of the oil changes dramatically with temperature. The MEN
heater is extremely troublesome in this regard because it runs the oil feed line around the hot flue
pipe. This is a mistake.
Why? Because having the oil line in contact with the flue heats the oil in the line as the stove gets
hot. This reduces the oil's viscosity, causing it to flow faster through the oil control valve. The
increased oil flow causes the stove to get hotter, which causes the flue to get hotter, which causes
the oil in the pipe to get hotter, which reduces its viscosity further, which causes it to flow faster,
which causes the stove to get hotter, which reduces the oil's viscosity more, which causes it to flow
What you get is a positive feedback loop, which causes the heater to get too hot and the oil flow to
become excessive. So after a few minutes, you have to turn down the oil flow, which reduces the
heat in the flue, which increases the oil's viscosity, which reduces the oil flow, which reduces the
heat, etc., until the fire goes out – unless you turn the oil flow back up again, which causes more
heat, more oil flow, etc. In short, the heater's operation is inherently unstable and unreliable. This
problem requires you to constantly monitor the oil flow and adjust it every few minutes.
Oil-flow stability is essential and it is impossible to attain as long as you have this positive feedback
loop problem. To reduce the problem, keep the oil feed line as far away from the flue as is practical
so that the temperature of the feed line remains relatively constant.
As the room heats up, the oil in the line will still become slightly less viscous and the flow will
increase slightly, which may require you to adjust it. But once you get the room at the temperature
you want, the oil flow can be set to maintain that temperature and it will be stable for a long period
of time – usually all day, unless the outside temperature changes significantly, which affects the
flow of oil from the outside tank.
The above change helps a lot, but doesn't completely solve the problem. Two additional things are
necessary to achieve truly stable oil flow.
First, it really helps to use a relatively high oil pressure. I eventually put my oil tank on a hill above
my shop, which gives me a 30-foot (9-meter) head of pressure. The increase in oil pressure
compared to having a tank just a couple of feet above my heater significantly helped stabilize oil
flow. While this added pressure makes adjusting the oil control valve more sensitive, the oil-flow
stability is very much improved.
I understand that many readers don't have a hill next to their shop upon which they can put their oil
tank. If so, just make every reasonable effort to place the tank as high as possible. Alternatives
include using compressed air to pressurize the tank – 10 to 15 psi is
plenty (0.69-1.03 bar) – or by using a small oil pump, although this
starts to make things complicated and requires electricity to
The other major problem associated with oil-flow stability is that
the typical "needle" valve found at hardware stores is not designed
to precisely control the flow of liquids. These valves are really
designed just to be small on/off valves. I found that these valves
gave me only one-eighth of a turn between minimum and
maximum heat on my heater. They need to be much more gradual
in their operation.
If you carefully inspect one of these valves, the reason for their
poor performance will be obvious. They are very crude and don't
even have a tapered needle as is necessary to precisely control
flow. They are built using the flat end of the shaft to cover or
uncover an orifice. And the orifice is about 3/16-inch in diameter
(5 mm), which is much too large for our use. As a result, just a tiny Photo #13
amount of shaft rotation results in a relatively large increase in oil
flow. This is unacceptable.
At the top of Photo #13, you can see the valve assembly. Below that I've placed the control shaft,
showing that it has a flat end. Below that, I've placed a proper "needle" valve shaft.
As if the lack of a needle valve isn't enough of a problem, the threads on the flat-end shaft are loose
and sloppy, which means that the valve will not necessarily be in the same position with regard to
the shaft's rotational position. As a result, you can't get reproducible flow settings based on the
position of the control shaft. This problem could be improved if a strong spring were used to hold
tension on the threads, but these valves have no such spring.
If you use one of these valves, you can improve the reproducibility of the settings by always
adjusting the valve in one direction only and pushing in (or pulling out) on the shaft the same way
every time you rotate it so you maintain a stable position between the threads. The valve settings
will still not be completely reliable and reproducible, but you will get some improvement.
The only real solution to this problem is to use a valve with a tapered needle and precision threads.
It is also very desirable to have a sight glass in the valve so that you can see the oil drops falling. By
watching the drip rate and checking a wood stove thermometer that you place on the side of the
heater, you can easily get excellent control of the heat output. Such valves are commercially
The oil drip valve should be placed close to the heater for precise oil control. I put mine right at the
entrance of the air tube. This area stays cool because air is flowing into the air tube.
The 1/4-inch (6.35 mm) copper oil feed line must run inside the air tube. This is because the oil line
must be kept cool enough that the oil in it doesn't boil. If it boils, vapors will spray out of the tube
and catch fire. While this won't hurt anything, ash will soon form around the end of the oil line and
clog it. The oil feed line should end about 2 inches (5 cm) from the end of the air tube so that it is
not exposed to the direct flame.
The oil feed line is cooled by the fresh air flowing through the air tube. Also the air tube blocks the
intense infrared radiation coming from the fire. So the oil in the tube remains liquid.
I installed a mica window in the door of my stove. This is a nice feature as you can see the flame,
but it gets covered in soot. I have tried many ways to prevent the soot from getting on the window,
but have not been completely successful. So a window isn't very practical.
It is better to just observe the flame by looking down through the air pipe. This is a bit awkward. To
make it easy, attach a small mirror at a 45-degree angle above the air tube. You can then look at the
mirror horizontally instead of straining to look down the tube vertically.
You will need a good filter to prevent your oil control valve from getting clogged up. Filtering the
oil through panty-hose is not good enough.
Waste oil always has water and/or antifreeze in it. Even if nobody put antifreeze in it, it will always
have water mixed with it as water is one of the products of engine combustion. The water will be
mixed into the oil as an emulsion, so it will not all just settle to the bottom of the tank where it can
be drained away just one time. The filter screen causes the water to separate from the emulsion, so
you will have to drain water frequently, usually daily as part of your start-up ritual.
Unlike water, antifreeze quickly settles on the bottom of the tank. If there is antifreeze involved
when you get a new tank of oil, you may have to drain water several times over a few hours until
most of the antifreeze is gone. Then draining water daily is sufficient. In any case, you will be
draining water frequently, so you need to make it fast and easy.
A good filter will have provisions for removing water. If you put a
quarter-turn ball valve in the bottom of my oil filter/water-separator,
draining the water only takes a few seconds. I installed a clear hose at
the outlet so I can see when the draining water turns to oil. Photo #14
shows this filter assembly.
Experience is the toughest teacher – she gives the test first, then the
lesson. So another issue I learned the hard way is that your oil feed
line must drain downhill at all times until it reaches the water/oil
separator. If there is any low spot in the line, it will accumulate water,
freeze, and prevent stable oil flow.
I originally put my oil line on the ground and then ran it up the side of
my shop where it made a very neat installation. But this formed a low
spot at the bottom of the wall, and this ruined my oil flow. I had to
elevate the line to get stable operation.
Photo #15 shows this suspended line. It isn't as neat as running the line Photo #14
on the ground, but it works perfectly.
It is interesting that nobody seems to mention the issue of
collecting oil. This is a major problem as you will burn
quite a lot of it over time. I burn 50-100 gallons per month
(190-380 liters) during sub-freezing weather to heat my
1,200 square foot shop (111 square meters) that has only
moderate insulation. So you must have a fast and effective
way to collect and store oil.
Collecting oil is a messy hassle, so you don't want to have
to do so any more frequently than necessary. In short, you Photo #15
want a big oil tank.
There is no cheap and easy solution to this problem. I
considered 55-gallon oil drums (200 liters), but when full,
these are heavy, hard to handle, and a nuisance to connect a
feed line to without spilling oil and making an environmental
mess. I quickly realized that I needed a serious oil transport
and storage system.
While my heater cost me nothing to build from scrap parts, I
had to spend about $500 to build a tanker/trailer and pump
system for my car. This consists of a small, inexpensive ($200)
trailer kit (from Northern Tool or Harbor Freight Tools) to Photo #16
which I mounted a 225-gallon (850-liter) plastic tank ($220).
Photo #16 shows this tanker/trailer.
When this tank is full of oil, the gross weight of the tanker/trailer is about 1,400 pounds (635 kg),
which is the maximum weight I care to pull with my car and it is the maximum weight allowed by
most small trailers. So don't get a tank that is too big unless you have a big, powerful tow vehicle
and a larger trailer that will handle the weight.
You also need some sort of hydraulic pump to transfer the oil to your tanker/trailer. While
commercial waste oil pumps are available, they cost hundreds of dollars and they don't pump oil as
fast as I would like. So I connected a used hydraulic pump to a 2-horsepower (1.49 kW) lawn
mower engine. This, with suitable plumbing, makes it easy to pump the oil.
Oil is thick and viscous, particularly in the winter when you will need to get it. It is hard to pump it
fast. My pump is powerful, but it still takes about 30 minutes to fill my tanker/trailer when the
temperature is below freezing. That's longer than I like to wait, but since I only need to collect oil
two or three times per year, it is acceptable.
When I get home with the tanker/trailer, I connect it directly to my heater's oil feed line and use the
tanker/trailer as my heater's oil tank. I use a 3/4-inch (1.9 cm) ABS plastic feed-line that is about
130 feet long (40 meters) to feed oil from my trailer (on the hill behind my shop) to my oil
filter/water-separator inside my shop. I only switch to a 1/4-inch (6.35 mm) copper line about 4 feet
(1.2 meters) above the heater.
Eventually I installed a larger, 1,600-gallon (6,500-liter) stationary tank. This makes it possible to
collect oil only in the summer when it pumps faster and being outside is more pleasant. I drain my
tanker/trailer into the big tank as often as I wish. I no longer have to worry about running out of oil
during the winter. In fact, with the big tank full, I have enough oil to last for at least three winters.
Theory of operation
This heater is extremely simple. But many readers are confused as to exactly how it operates. This
generates a lot of questions in my e-mail. So let me explain exactly how the heater works and how
to operate it.
This discussion will be very detailed so that every common question is answered. Please read this
section (and the next on practical points of operation) carefully, because if you have questions,
you'll probably find the answers here.
The heart of the heater is the flue. Yes, the flue. That is because the flue is the "engine" that powers
the flow of gases through the heater.
Hot exhaust gases in the flue are lighter than the air around them, so they rise. As they do, they
draw a small vacuum inside the heater shell. This vacuum "sucks" air down the open air tube. This
downward flow of air is directed at the center of the burner.
Note that the vacuum caused by the flue makes it possible to have air leaks around your door with
no problem. Any leaks in the heater's shell will result in a little air being sucked through them into
the heater rather than having any smoke or fumes come out into your room. So it is not necessary to
have a perfectly airtight door.
Liquid oil will not burn. It must be vaporized to a gas. The burner is hot enough to boil the oil that
is in it and the oil changes state from a liquid to a gas, just like boiling water changes to steam. This
is called vaporization. As the oil vapors flow off the oil pool, they mix with the fresh air from the
air tube and start to burn.
The air coming down the air tube forces the flames to flow horizontally off the burner. They do not
flow vertically upward into the air tube.
The horizontal flames form a ring of fire around the burner – what I call a "flower of flames." These
flames lick the sides of the heater shell and quickly and efficiently transfer their heat to the heater
The hot heater shell transfers its heat out into your room. It does so by producing a lot of infrared
radiation that you can feel from several feet away, and by heating the air next to it (convection).
The larger the surface area of the heater shell, the more heat will be transferred to your room. So
using a large heater works better than using a small one.
The heat transfer to the heater's shell is quite good in this heater design, so very little heat is wasted
going up the flue. The flue gases are relatively cool. The flue doesn't get very hot. In short, the
heater is quite efficient.
Practical points of operation
There are several practical issues that you need to keep in mind when operating the heater. The first
is to take care of the heater's "engine." This means that the flue must be tall enough to work well
and produce a strong draught.
Your flue must be a minimum of 9 feet tall (2.7 meters) – and taller is even better. Ideally, it should
be dead vertical with no bends or horizontal sections. Don't expect the heater to work with a "stub"
flue that is only 3 feet tall.
If you simply can't install a completely vertical flue (such as if you must run the flue through a
wall), there are several things you can do to minimize problems. The first is to use 45-degree
elbows in the flue instead of 90-degree ones. By doing so, you will avoid having any horizontal
sections of flue and the exhaust can rise upwards throughout the entire flue.
Horizontal sections of flue simply should not be used. You can make it work with 45-degree
sections of flue instead. And any section of flue that is at 45 degrees should be duplicated by a
similar amount of vertical flue.
In other words, if you have a 10-foot (3-meter) run of flue, but 3 feet of that is at 45 degrees, you
should add an additional 3 feet of vertical flue to compensate. So the total length of the flue will be
increased to 13 feet (4 meters).
Soot will accumulate in the flue. It will eventually clog the flue and the heater will misbehave
(which I will discuss shortly). So the diameter of your flue must be a minimum of 6 inches (16 cm).
Larger is better, but a 6-inch flue is about as large as you can fit into most water heaters that will be
used for this project. A 4-inch flue will work if perfectly clean, but soot will quickly clog it. So use
at least a 6-inch-diameter flue.
The amount of soot that accumulates in the flue will vary depending on the oil you are burning. I
generally find that I need to clean the flue every 300 to 500 hours of operation for motor oil. When
in doubt, clean more often.
Note that most flues are designed for wood stoves. This means that the cap on the top of the flue
pipe will have a screen in it that is intended to catch sparks and glowing embers to prevent wild
These screens quickly become clogged with soot. So remove them. Oil stoves don't make sparks
and embers, so there is no risk of them causing a wild fire.
The soot is not flammable like creosote deposits that accumulate in a wood stove flue. So there is
no risk of a flue fire in an oil stove.
The soot is soft and easily removed. You do not need to use a stiff brush like you would to remove
creosote in a wood stove. Certainly a flue brush will work very well to clean the soot, but it sure
will be messy. Using a brush requires you to get up on the roof, which in winter with snow and/or
ice on the roof is risky.
To make cleaning the soot fast, easy, and relatively clean, I blast compressed air up my flue. This
blows the soot out onto the roof where the wind blows it away or the rain washes it off. This is a lot
better than brushing buckets of soot into the heater and then having to shovel it out.
To use compressed air, I put a 1-inch (2.5 cm) hole in the heater shell right at the base of my flue. I
can stick a blow gun in there and blast the soot up the flue. I plug the hole with a pipe plug or small
metal plate when I'm done.
In my experience, compressed air will only blow through about 8 feet of soot (2.4 meters). Since
my flue is 12 feet tall (3.7 meters), I have an additional 1-inch hole about halfway up the flue. To
clean the flue, I blow out the upper section of flue first, then blow out the bottom section, whose
soot can then pass freely through the upper section. I have a small metal plate that I screw over the
upper hole when I am done cleaning it.
Air tube restrictor
The air tube restrictor is extremely important. It is absolutely essential that the air flow be severely
restricted for the heater to operate properly! Many readers incorrectly believe that they need a large
amount of air flow to make the heater burn "cleanly" and "efficiently." Just the opposite is true.
Why? Because if excessive air flows into the heater, it will blow the flames off the burner. If the
flames are only burning around the outer edge of the burner, the heater will produce very little heat
(poor efficiency), the heater will be very unstable, and most likely you will have a spontaneous
I cannot stress this enough – the flames must be over the burner at all times. Too much air will blow
the flames off the burner. You must severely restrict the air flow for efficient operation.
Excess air will not blow the flames off the burner if the burner is really hot. So it is possible to open
the restrictor more once the heater is really cooking. But doing so will not improve combustion.
Once the oxygen needs of the burner are met, the only thing excess air will do is cool off the heater
shell and drive the hot gases out the flue before they have had time to transfer as much heat as
possible to the heater shell.
So avoid the urge to use more air to get a "cleaner" burn. It doesn't work that way. Trust me – use
the most restriction possible for best heater performance.
So how do you know how much restriction to use? You can tell by watching the flame on the
burner. A "normal" flame that has adequate air for complete combustion will be highly energetic
and be mostly yellow in color with streaks of white in it. An oxygen-starved flame will be sluggish,
orange in color, and very smoky.
The amount of air required will be about the amount that will flow through an area of about 1-1/2
square inches (9.7 sq cm). This will be a hole about 1.3 inches (3.3 cm) in diameter. If you are using
a restrictor with a straight side, you will want to close off about 80% of the air tube, which will be
all but about an inch (2.5 cm) of the air tube opening.
Many readers are concerned about wasting a lot of warm room air feeding the air tube and the fire.
But you can see that if you use an appropriate amount of restriction, the amount of air sucked into
the heater will be very small. So it isn't a problem.
However, if you want to plumb in outside air, feel free to do so. The only disadvantage will be that
you can't look down the air tube to see the flames and monitor the heater.
Lighting the burner
Fill the burner with kerosene. It needs to be completely full. So be sure the burner is level. If
necessary, shim your heater or the burner pedestal so the burner is level.
A turkey baster works well for filling the burner. They are cheap and readily available from food
stores. The bulbs on these are usually latex, which kerosene will gradually dissolve. But if you store
the baster with its point down, kerosene will run out of the bulb and it will last a long time.
Light the pool with a lighter or propane torch then close the door.
You would think that the flame and smoke would go straight up the air tube at this point. But it
usually won't if the door is closed.
The reason for this is that the air tube is restricted, while the rest of the heater is wide open space
with a big flue opening at the top. The flames find it easier to go out into the heater space and up the
As soon as they do (it may take a few seconds), air will start to be sucked down the air tube. You
can feel the cool flow of air near the inlet of the tube with your hand.
If your heater blows smoke out the air tube, then it is almost certainly because you have a flue that
is clogged with soot. Cleaning the flue should fix it.
If your heater has a clean flue and still blows smoke out the air tube (very unlikely), you can always
close the air tube completely with the restrictor plate or with your hand. After 10 or 15 seconds,
enough hot gases will have been generated inside the heater that you can slowly open the air tube
and air will be drawn into it normally.
Note that smoke will go up the air tube if you have the door open. This is because the flue vacuum
will draw air in more easily through the relatively large door than through the restricted air tube. So
when the door is open, no air will come down the air tube and the flames can and will go up it.
You will need to start the oil flow at some point after the burner has been lit. You can do this
immediately or wait for a minute for some of the kerosene to burn away. Either way works. But you
must avoid flooding a cold burner with raw oil or the flame will go out and oil will flow over the
burner into the bottom of the heater.
So start with a "low" oil flow. This means an oil drip rate of 2-3 d/s (drops per second) as seen in
the sight glass in the valve.
Usually the kerosene will get the burner hot enough that there will be sufficient heat for the burner
to vaporize 2-4 d/s of 5W-30 motor oil from a cold start. Until you become familiar with your
heater's behavior, you should wait and observe it for at least 10 minutes after you light it to be sure
that it doesn't flame out.
Sometimes a single shot of kerosene won't get the burner hot enough to sustain oil combustion. This
is unlikely with 5W-30 motor oil, but if you use heavier petroleum oil or veggie oil, the burner will
need to be hotter. If the flame keeps going out, you need more heat.
You can get more heat by using a second shot of kerosene. However, you must be careful to avoid a
flash fire when adding more kerosene. Fortunately, it is easy to avoid. Here's how:
Understand that if you put kerosene into a hot burner that has no flame, the kerosene will vaporize
into a fog inside the heater shell. If you then attempt to light it, the kerosene vapors will suddenly
ignite, causing a big blast of flame to come shooting out the door of your heater.
This small explosion probably won't harm you, but it will most certainly get your attention. You'll
probably be missing some eyebrows and other body hair that gets burned off by the flash fire.
To avoid this, NEVER PUT KEROSENE INTO A FLAMELESS HOT BURNER!
But it is perfectly safe to put kerosene into a burner that has flame on it. The flame will ensure that
the kerosene vapors are burned as fast as they form. This will prevent an accumulation of kerosene
vapor that can explode.
So to get your burner really hot, light a load of kerosene, close the door, and wait. Do not start an oil
Wait until the kerosene is mostly burned away (about two minutes). Then open the door, assure that
flames are still present, and squirt in another shot of kerosene. Close the door and wait another
By now the burner should be hot enough to burn even difficult oil. So start a slow oil flow (2-3 d/s).
The fire should be self-sustaining over the next five minutes. If so, you can walk away and let the
fire heat up the stove. You should let the heater warm up on "low" for about 15-20 minutes.
You should have a wood stove thermometer on the side of your heater at the level of the top of the
burner. This will be the hottest location in the heater.
Wood stove thermometers can be obtained at any wood stove store and at most hardware stores.
Most are round and use a bi-metallic coil to operate a needle that points to the temperature. They
are cheap, typically costing less than $20.
These thermometers usually are mounted with a magnet. However, an oil stove gets much hotter
than a wood stove and at high heat the magnet will lose its strength and the thermometer will fall
off. So get one that has a hole in the middle that you can use to screw the thermometer to the heater.
At the end of the warm-up period, the thermometer should show a temperature of at least 250
degrees F (121 degrees C). I consider this "low" heat.
After a successful warm-up period, you can then increase the oil flow to get it hotter. Keep in mind
that if you increase the oil flow too much, too suddenly, you will flood the burner and extinguish the
So increase the oil flow by no more than 100%. For example, if you have been running 3 d/s,
increase to no more than 6 d/s.
Let the heater run for another 15-20 minutes before increasing the oil flow again. If you doubled the
oil flow, the temperature should be about double the previous temperature – probably around 500
degrees or more (260 degrees C). I consider this "medium" heat.
You can double the oil flow again. By now, you will probably see a thin, steady stream of oil rather
than distinct drops. Again, wait 15-20 minutes. The temperature may climb to over 800 degrees
(427 degrees C), which is hotter than you are likely to want or need.
After another 15 minutes, you can increase the oil flow more. But you probably do not need more
heat and you will be pushing the limits of the heater as the temperature exceeds 1,000 degrees (538
degrees C). At some high oil-flow rate you will "overfire" the heater.
How will you know when you have overfired the heater? The heater will start to shake and vibrate
violently as smoke and soot start puffing out of the air tube and from around leaks in the door.
What is happening is that you are burning more oil and producing more exhaust gas volume than
the flue can extract from the heater. When this happens, exhaust gases develop pressure inside the
Remember that in normal operation, there is a slight vacuum inside the heater as the flue gases are
trying to pull air past the air tube restrictor. But now there is more pressure inside the heater than
outside. So the exhaust gases start going up and out of the air tube.
When the exhaust gases are going up the air tube, air cannot get into the heater to burn the oil
vapors that are forming. So the fire starts to go out.
As the fire dies down, the exhaust gas volume diminishes. As it does, the flue "catches up" and
starts to draw air back down the air tube.
But keep in mind that during this period of time, although the fire has died down (due to lack of
air), the burner has continued to vaporize oil. As a result, there is now a large fog of unburned oil
vapors inside the heater. When the air comes back down the air tube, these vapors can now get
oxygen and burn and are ignited by the small flame that is still present.
You now get an explosion, just like the kerosene explosion I described previously. But because the
door is closed, the blast of flame can only go back up the air tube rather violently.
This once again causes the fire to die down, vapors to form, the flue catches up, the air comes back
down the air tube, and you get another explosion.
These explosions are small (they don't blow up the heater) and occur several times per second. But
they make the heater shake violently and belch smoke, soot, and fumes all over your room.
I don't think that overfiring the heater is dangerous, although obviously it should be avoided. If left
unattended, the condition will self-correct as the violent pulsations inside the heater eventually put
the flame out.
But you can stop the action immediately by simply covering the air tube with the restrictor plate
(which will probably have been blown off the heater and is lying on the floor somewhere nearby).
By covering the air inlet, you will prevent air from flowing back in to cause more explosions.
But don't leave the air tube completely covered for more than a few seconds, or the fire will go out.
Most likely, you'd like to keep the fire going because it's cold outside.
So promptly open the restrictor plate a little. Just a 1/4-inch opening (6.35 mm) will be enough to
keep a little fire going until the oil flow gets back under control.
Once you have stopped the violence by closing the restrictor plate, immediately shut off the oil.
Within about 30 seconds, the excess oil in the burner will have vaporized and exited the flue. You
can then open the restrictor to its normal position and turn the oil back on – but of course, to a
somewhat lower oil-flow rate.
Note that the burner will be extremely hot during an overfire condition, so the oil in it will vaporize
very quickly. Therefore do not wait long before turning the oil back on or you will lose your flame.
If you do have a flame-out, remember that the burner is hot so you cannot put kerosene into the
burner. You can, however, put oil in the burner. It will vaporize and smoke, but it won't explode
because you are only letting in a few drops per second rather than a big load from a turkey baster.
So open the oil valve and light the oil directly with a propane torch. It should ignite and you can
close the door and all will be back to normal.
Of course, you will then need to open the doors and windows to get rid of the smoke and fumes.
You'll probably have to sweep soot and ash up off the floor.
I've discussed the overfired condition in detail because sooner or later you will probably experience
it. You won't know how much oil you can feed your heater until you do. So just be calm, know that
it isn't dangerous, and go stop it.
Note that the oil-flow threshold that causes overfiring is not constant. This is because soot in the
flue will reduce the capacity of the flue. A badly clogged flue will result in overfiring even at just
moderate oil-flow rates. So any time your heater misbehaves, such as smoke coming out the air tube
at start-up, overfiring, or unexplained flame-outs, suspect a clogged flue.
An unexpected flame-out will result in oil filling up the burner and overflowing into the bottom of
your heater. Because the heater shell will hold a couple of gallons of oil before it runs out the door,
most of the time you will discover the problem before oil spills into your room – at least, I hope so.
So what do you do about flame-outs? If there is just oil in the bottom of the heater, remove most of
it with a cup and then suck as much out as you can with the turkey baster. This will be a mess
because of the ash with which it is mixed. But do the best you can.
You can then burn the remaining oil in the bottom of the heater. Before doing so, remove the
WARNING: Never start a fire under the aluminum burner. Doing so will melt it. The burner must
only have fire on or above it.
With the burner removed, you can light the oil in the bottom of the heater using a propane torch.
Just heat one area. The ash will act like a wick and help keep it going. Once things get hot, the oil
flame will be self-sustaining.
You must be careful to avoid an excessively hot burn when so much oil is present. You will need to
use the air restrictor plate to keep the temperature under control. Tend the heater at all times during
this process and adjust the restrictor to keep the temperature below 600 degrees (316 degrees C).
There will be more smoke than usual during this burn because much of the oil vapor formed will
not burn and will simply go up the flue as dense smoke. This burn may take an hour or more
depending on how much oil was left in the bottom of the heater. Once the fire has burned out, you
can reinstall the burner and return to normal operation.
If you have spilled oil on the floor, you can get oil-absorbing "kitty litter" from any auto parts store.
You sprinkle this stuff on the oil and sweep it around while it absorbs most of the oil. It will trap the
oil so you can sweep it up and throw it away.
I made this heater very simple for ease of building and operation. But this requires that you tend to
it much like a wood stove. It is certainly easier to operate and tend than a wood stove, but you
should not leave it unattended for long periods unless you install some safety features (more on this
So what causes flame-outs? In my experience, they are usually caused by water in the oil. You
should be using an oil filter/water-separator, but even so, you have to drain the water regularly. If
the water separator becomes full, water will get to your heater and put out the flame.
Other causes include a flue that is clogged with soot, overfiring the heater when you are not present
to stop it, running too much oil into a cold burner at start-up, and failing to restrict the air tube
The design of the heater is very crude, non-critical, and easy for most DIYers to build with common
tools. You don't have to build a heater exactly like mine to make it work. You can feel free to
change most things to fit the materials you have available. For example, while my heater is made
from a 40-gallon (150-liter) water heater tank, you could use a different size water heater, an old
propane tank, a wood stove, or a piece of large steel pipe. You can make the door larger or smaller
or in a different location. You can use many different things for the burner's pedestal, etc.
But there are a few rules that should be followed:
1) Use a minimum of a 4-inch (10-cm) diameter air tube.
2) Use a minimum of a 6-inch (15.2-cm) diameter flue.
3) Use a burner of at least 5 inches (12.7 cm) in diameter.
4) A larger/taller heater will be more efficient than a small one.
5) The burner should be 5-7 inches (13-18 cm) below the bottom of the air tube.
6) The air tube must be vertical for at least a foot (30 cm) above the burner.
7) Use adequate air-flow restriction (usually at least 80% restriction).
8) The flue must be a minimum of 9 feet (3 meters) tall.
9) The oil line must run inside the air tube.
10) The oil line should stop about 2 inches (5 cm) from the end of the air tube.
I'll describe how I made my heater just to give you ideas and suggestions. But you can be as
creative as you like.
I made my heater from a gas-fired, 40-gallon water heater (150 liters). I stripped all the covering
and insulation from it, removed the water pipe fittings, and welded the openings shut.
Note that water heaters usually have a coating of glass on their interior to prevent the steel from
rusting. You may ignore the glass. It doesn't melt inside the heater and it appears to prevent any
deterioration of the steel. The interior of my heater looks the same as it did five years ago when I
first built it.
I made my air pipe by using the 4-inch (10-cm) gas flue that was
already present inside my water heater. I'll admit that cutting
this pipe inside the heater, removing the bottom section, and
welding up the hole left in the bottom can be difficult unless you
have a well-stocked tool shop.
So you may well find it more practical to take MEN's advice
and use an electric water heater tank, which doesn't have a flue.
You can then cut an opening in the center of the top for a 4-inch
pipe that you can mount in the center of the tank, directly above Photo #17
the burner, using MEN's fabrication technique: Air tube and flue fittings on an MEN
heater built by Journey to Forever
First the holes on top of the tank are chalked, and then cut,
using an electric saber saw (if you don't have one, MEN recommends that you rent one for a few
hours). Cut the openings a little on the small side, and then spend a few minutes filing them out
to size. The flue and air pipe are secured with bolts and 3/4-inch-wide angle iron tabs.
I cut some 1-1/2-inch steel strap (3.8 cm) and welded the ends together to make a collar for a 6-inch
flue (15.2 cm) beside the air pipe. If you don't have the tools needed for this, use the technique
shown for the MEN heater.
The conical burner sits on a pedestal in the heater. No bolts or
fasteners are needed or used. Photo #18 shows the pedestal, which
is made from water pipe and floor flanges. Photo #19 shows the
conical burner sitting on top of the pedestal.
I cut the door using a 3-inch (7.6 cm) cut-off wheel in a die grinder.
If you use a very thin wheel, you can get a very narrow kerf.
Cut the door about a foot square (30 cm) and remove it from the
heater shell. You will need to line the inside edge of the door
opening with some sheet metal so that the door can close against it.
A couple of cheap cabinet hinges can be used to hang the door and
a simple clamp can be used to hold the door closed.
The door does not have to be airtight or have a gasket to seal it. But
it is best if the fit is reasonably good. Photo #18
The only problem with the conical burner design is building it. The
burner must be machined on a lathe because there is no common
hardware store item that is anything like it. I have a machine shop,
so this presented no problem, but the average amateur builder will
have to have a machine shop make this part. I now machine these
and have them in stock for DIYers (see details at the end of this
The burner needs to be level as it is very shallow. You will either
need to put adjustable feet on your heater or use metal shims to
The heater size is not critical. But keep in mind that the heater will
heat the air more efficiently if it has a large surface area. So a
small, squat heater may look nice, but it won't be efficient. Since
floor space is the major space issue, and height isn't, I used a small-
diameter, but tall heater to get adequate surface area.
Your stove should be painted flat black to maximize radiation efficiency. The high-temperature
paint (1,200 degree F, 650 degrees C) used on wood stoves works well, although the oil heater can
get so hot that it burns the paint off. Expect the paint to smoke a lot the first time you fire up the
heater, so be prepared to ventilate your room.
Please use a safe flue! It makes no sense to build a heater that uses free fuel and then have its flue
burn your house down. Your roof opening should be lined with metal and a triple-wall, insulated
pipe should be run through it. If you are uncertain how all this is done, check with anyone who
installs wood stoves for guidance.
The surface temperature of an oil heater can exceed 1,000 degrees (538 degrees C). So it is essential
that you use safe installation practices. You should follow the safety guidelines for wood stove
Specifically, this means that the heater must be at least 4 feet (1.5 meters) from any combustible
surface. It must sit on a non-combustible surface like concrete, steel, or tile. The flue must be
insulated where it goes through the roof, and the rafters and other combustible surfaces in the roof
must be shielded by sheet metal.
Burning vegetable oil
Although I burn waste motor oil in my heater, I recognize that many readers will want to burn waste
vegetable oil. So I did some experiments with my conical burner to see how it handled vegetable
oil. I did not have any used vegetable oil, so all tests were done using new, generic, vegetable oil
bought from the food store.
First, it is obvious that vegetable oil doesn't burn as readily as motor oil. The burner must be
brought to a considerably higher temperature than needed with motor oil to initiate and sustain
combustion of pure vegetable oil. I was unable to obtain vegetable oil combustion using only a
single shot of kerosene as the starting fluid. But once started with a second shot of kerosene, veggie
oil burned okay. A pool of liquid vegetable oil formed on the burner and the heater ran reliably and
cleanly using only pure vegetable oil.
I could even turn it down to a rather low setting without the heater "flaming out." The heater prefers
to run a bit hotter with vegetable oil than what is needed with motor oil. However, it can be turned
down to a low enough setting with vegetable oil to still produce a reliable flame that is not too hot.
At the opposite extreme, vegetable oil doesn't get the heater quite as hot as does motor oil. But it
runs plenty hot enough.
For ideal combustion, I found that vegetable oil needs a bit more air than does motor oil. I found it
burned cleanest (virtually no smoke) with the air restrictor opened up from 2 inches to 2-1/2 inches
(5 to 6.4 cm).
Fuel consumption was quite reasonable. I found that at a low setting the heater consumed about 6
ounces (0.18 liters) of vegetable oil per hour. At a moderate setting, fuel flow was about a quart per
hour (0.95 liters).
I didn't burn enough vegetable oil to get a really good feel for the type of ash produced, but after
burning the vegetable oil that I bought, I found that there was some soft ash that was all black
(unlike motor oil "ash", which is light in color). But it was very easy to remove. So I think that
burning vegetable oil will make cleaning the heater quite easy.
In summary, the heater will run quite well on vegetable oil.
Improved starting system
While the heater is easy to start by squirting kerosene into the burner, this is not convenient or
clean. Also, sometimes it doesn't produce enough heat to burn difficult fuels.
Starting can be made easier and more reliable by installing a small tank (1-5 gallons, 3.8-19 liters)
of starting fuel (kerosene or gasolene) above the heater. Connect this tank to a "T" in the oil line
such that you can introduce starting fuel to the oil feed tube through a separate drip valve.
Then when you want to start the heater, you simply start a flow of starting fluid through the valve at
a brisk rate and light the burner. You can then turn on the oil at a low rate and let the two mix and
flow into the burner.
The starting fluid will guarantee that the oil will burn and the burner will heat up very quickly. After
about five minutes (depending on the type of oil you are using), you can turn off the starting fluid
valve and the heater will sustain oil combustion.
If you have a fuel that is very difficult to burn (like synthetic oil or heavy gear oil), you can keep a
small flow (1 d/s) of starting fluid running at all times. This will ensure that the difficult fuel will
The heater design described above is simple, reliable, easy-to-use, and solves the problems
associated with vaporization waste oil heaters. It uses no electricity, is quiet in operation, has
reliable oil flow, has a wide heat range, and is easy to clean and light. In other words, it is a
practical design that you can use day in and day out for seriously heating your garage or workshop
without costing you a lot of time and frustration.
But many readers have expressed a desire to have a more automated heater that can do more (such
as heat their home) and requires less attention. The heater I actually use is self-cleaning and it
operates under thermostatic control. It has safety features so there is no possibility of an oil spill,
and I only have to clean it once a month.
Such a heater is much harder to build – beyond the ability of most DIYers – and it requires
electricity to operate. So the simple heater described above is best for most users. But due to
popular demand, I am including the following discussion that describes how to build an automated
version of the heater.
This is a general discussion and will give many ideas for automating your heater. But because such
a heater requires custom fabrication, I will not provide any detailed plans because you will have to
be creative and develop your own automation systems.
There are three issues to address for automation:
1) Obtain automatic oil flow.
2) Make the heater self-cleaning so you don't have to clean it every day.
3) Safety features (automatic shut-off if there is a flame-out).
The drip system described above works very well with occasional monitoring, but the oil flow is
unstable with temperature changes and therefore unsuitable for unattended operation. You either
need to make a temperature-controlled needle valve assembly or use oil pumps.
An automatic, regulated, thermostatically controlled oil feed can be made to work without
electricity. I have not made a thermostatically controlled, gravity-fed drip system because I use oil
pumps, but certainly one could be made.
Conceptually, it is quite simple. A bi-metallic element (such as what is used in a thermostat) could
be connected mechanically to either a needle valve or a disk valve such that as the temperature
increased, the bi-metallic element would reduce the oil flow by either moving a tapered needle into
an orifice or by putting pressure on a flexible disk – and vice versa.
The system would have an adjustment knob so that you could adjust the tension on the bi-metallic
element to control the temperature – similar to a typical thermostat.
I'm sure such a device could be built and that it would work beautifully. If you make one, please
send me the details.
I use constant displacement oil pumps to obtain a constant and automatically controllable oil flow.
Suitable pumps are difficult to find. While there are many chemical metering pumps available
(check eBay), most pump too much volume, are incompatible with petroleum products, and have
short life spans.
There are two general types of positive displacement chemical pumps. One uses peristaltic motion
where a flexible tube is squeezed along its length to push fluid through it. The tube fits inside a
cylinder and there are rollers on a wheel which is turned by a gear motor that pushes fluid through
the tube as the wheel turns. I don't consider these suitable as the flexible tubing will fail rather
quickly with constant use.
The other type is a diaphragm pump. These have a diaphragm that is operated by a crankshaft.
There are check valves at the inlet and outlet to provide constant volume flow. By using a very
small diaphragm motion, long-term reliability can be very good.
Diaphragm pumps are normally driven by small gear motors. Such motors turn at high speed, use
journal bearings, and so have a life span of about 3,000 hours. Since the pumps will need to run
more or less constantly, they will be worn out in less than a single heating season.
I use diaphragm pumps and replaced their gear motors with "Slo-Syn" motors. These motors have
so many poles that they operate at only 72 rpm, direct drive. They use double-sealed ball bearings
and will operate for millions of hours without attention.
Adapting a Slo-Syn motor to a diaphragm pump usually requires a lathe. If you have access to one,
I recommend making a Slo-Syn motorized diaphragm pump. You will need to change the "O" ring
seals in the valves to handle petroleum. My pumps have worked for four years without failure.
I use two pumps. This is because an oil heater cannot be automatically started easily like a propane
The first pump is used to keep the heater running continuously on "low" (about 7 ml/minute). The
second one is controlled by a common, programmable, wall thermostat to increase the oil flow (by
an additional 10 ml/minute) when more heat is needed. This system works perfectly.
To prevent any possibility of an oil spill during unattended operation (I leave my heater on
continuously, including at night), I run the power to the pumps through a safety thermostatic switch.
This switch is set at 120 degrees F (49 degrees C). If the temperature of the heater falls below that,
such as during a flame-out, the switch opens and stops the pumps.
Such switches are readily available for less than $20 from any wood stove store. They are used to
switch on blowers that are commonly used on wood stoves.
As should be obvious, you will also need a small switch to bypass the safety switch when starting
the heater. Once it gets hot, the thermostatic safety switch will close and you can then open the
bypass switch for safe operation.
I could write a book on my experiences trying to build a self-cleaning burner. This has turned out to
be one of the most difficult and frustrating devices I have ever engineered and built. It has taken me
three years of experimenting to get reliable operation.
My system is quite simple. I rotate the burner under a sharp blade that scrapes off the ash as the
burner rotates under it.
The main problem with a self-cleaning burner is that I mistakenly expected it to be easy to scrape
the ash off the burner. I made this false assumption because the ash is very easy to remove when the
burner is cold.
But I have discovered that the main reason for this is that the aluminum burner contracts greatly
when it cools off, and this breaks the hard ash off the burner so it virtually just falls off when you
hold it in your hand to clean it.
A second reason is that the ash that accumulates on the burner is very porous. This makes it easy to
scrape it off the burner.
But when the burner is hot and you keep scraping the ash off it, the ash neither breaks away from
the burner nor becomes porous. As a result, the ash takes on the character of polished marble rather
than loose, fluffy ash. So you have to make your cleaning system extremely rigid, strong, and
My early attempts at self-cleaning used a small gear motor and relatively weak scraping blades, and
either the motor would stall or the scraper broke. As I made the assemblies stronger, I found that an
aluminum burner would actually warp and droop and finally break apart. I also had constant bearing
failures as they could not withstand the heat and pressure inside the heater.
Experience has shown that I need a powerful motor system, an extremely strong scraper blade, an
ash distribution system, a secondary scraper blade, a super-strong burner, external bearings, a
massive drive shaft, and a pulse timer. Here are the details of my current system:
Photo #20 shows my gear motor system. I'm using a 1/4-horsepower motor (0.18 kW) driving a
300:1 dual worm-gear box. The gearbox rotates at 6 rpm and can handle 20 horsepower (14.9 kW).
Because the burner support bearings have to withstand
severe radial loads and high heat, I never could get bearings
to hold up when they were inside the heater. The biggest
problem with such internal bearings is that the heat causes
their ball separators to lose their temper, distort, and either
jam up the bearing or fall out, leaving the balls to move to
one side of the bearing, where they fall out and the bearing
Also, due to the heat, the bearings cannot be sealed or Photo #20
effectively shielded. So they must survive without
lubrication and they must tolerate having foreign material getting into them.
The solution is to keep the bearings outside the heater. This requires a long shaft to extend from the
gearbox up inside the heater. This increases the loads on the bearings due to cantilevering, but the
bearings can be very large, oil-cooled, and sealed. The ones in my current gearbox are tapered
rollers and are completely submerged in an oil bath. They have been 100% reliable.
The drive shaft is 1-1/2-inch in diameter (3.8 cm). It has a keyway to handle the torque.
Photo #20 shows this motor/gearbox assembly welded to the bottom of my heater.
When an aluminum burner is hot, it has poor strength, and the pressure of the scraping action of the
blade is so high that it causes the burner to deform and sag. So the burner must be made of thick
The primary scraper blade is made of tool steel that is 1/2-inch wide and 1 inch tall (1.3 x 2.5 cm).
It takes this much strength to handle the load, even though the cantilevered end of the blade is only
3 inches long (7.6 cm). I've had lesser steel alloys and smaller blades just bend under the scraping
The blade must be very strongly attached to the heater so that it can scrape the burner with
sufficient force. The blade holder is made as a three-piece steel assembly that triangulates the blade
to two points on the side of the heater, 90 degrees apart, and a third leg is welded to the bottom of
the heater. This lower leg must be very strong as the blade is forced upward with tremendous
pressure as it scrapes the burner. I have had 1/4-inch-thick (6.35 mm) steel snap from the tensile
Note that you cannot weld the scraper blade to its holder. Welding embrittles the blade and it will
snap off. I solved this problem by using a carbide drill to drill a pair of holes in the tool steel blade.
The blade can then be mounted with grade 8 bolts to the triangulated holder.
The primary scraper blade will accumulate ash just like the burner does. The ash will eventually
spread out over the top of the burner forming an "umbrella." If such an umbrella forms, it will catch
the oil and direct it over the edge of the burner into the bottom of the heater. So this umbrella cannot
be allowed to form.
To break up the ash on the primary scraper blade and prevent an umbrella from forming, I use a
secondary scraper blade that is welded to the center of the burner. This blade can be relatively
small, but it still must be quite strong. I use a 3/8-inch-thick (1 cm) Allen key and it extends up and
radially out over the primary scraper blade.
As the burner rotates, the secondary blade scrapes the ash off the primary blade. For reasons I do
not understand, the secondary scraper blade does NOT accumulate significant ash, so thankfully, it
is not necessary to figure out a way to keep it clean. Note that neither of the scraper blades actually
contacts the other blade or the burner.
The blades can ride as much as 1/4-inch (6.35 mm) above the surface they need to keep clean and
they will still work. Amazingly, any gap between the surfaces will quickly fill with hard ash and
produce a new, hard surface that will require forceful scraping to clean. So the problem of high
forces cannot be eliminated simply by putting space between the parts.
It is also essential to use a sharp scraper blade and be sure to use plenty of relief behind the scraping
edge. Obviously, if debris can build up under the blade from insufficient relief, the cutting edge
cannot contact the ash and the blade will be forced upward with so much force that failure is
Photo #21 shows the burner, scraper blades, and distrib-
I have found that the system works best if it does NOT
run continuously. It is better to let a small amount of ash
build up and then scrape it off rather than scraping the ash
continuously. By letting it build up, it is not as hard as the
almost polished ash that is produced by continual
scraping. It also saves the cleaning parts if they are not
actually used very much. Finally, the system is noisy, so it
is best to run it infrequently.
To achieve this, I use an ordinary timer from a hardware store. Some of these have 12 or more
settings per day. I set my cleaning system to turn on every two hours and the cleaning cycle runs for
just two minutes each time.
The ash that comes off the primary scraper blade quickly builds up in a heap under the blade. You
will need to spread this around the inside of the heater or else you will have to clean it out every
few days. To do this, I attached a steel vane to the drive shaft. This sticks out about 2 inches (5 cm)
from the shaft and as the shaft rotates, the vane catches the pile of ash and distributes it around the
circumference of the heater.
These systems make it possible for the heater to operate unattended for a month at a time while
keeping my shop at a constant 70 degrees F (21 degrees C). Flame-outs are very rare, but if they
happen there is no significant oil spilled. Perhaps an ounce of oil will overflow into the bottom of
the heater before the pumps switch off, but I can ignore it and it will evaporate once the heater is
back up to temperature.
Hot water and home heating
Waste oil heaters can be used to heat water – either for domestic hot water or to heat your home
using radiators. Safety is the problem. An oil heater gets very hot and can easily boil the water in a
water tank or in water-circulation pipes. Of course, boiling water produces steam, which can cause
an explosion. So it is absolutely essential to install "pop-off" safety valves that will vent the tank
and/or tubing in case the pressure rises too high. These valves are always used in all water heaters
so they are readily available at reasonable prices.
You should also install a safety shut-off solenoid valve in your oil supply line. This should be
controlled by a thermostat in your water system so that the valve will automatically turn off the oil
supply to your burner if the water temperature exceeds a safe level – probably around 190 degrees F
(88 degrees C). It should have a second thermostat to turn off the oil if you have a flame-out.
Always assume the worst because Murphy's Law assures it will happen. You remember Murphy's
basic laws, don't you? I'll refresh your memory:
1) Nothing is as easy as it looks.
2) Everything takes longer than you think it will.
3) If anything can go wrong – it will – at the most inconvenient time.
Murphy has many other laws, but these give you an idea of what you are up against. All mechanical
devices will eventually fail. So think about what will happen when something like your water
circulating pump fails and the water in the piping in your heater doesn't move while being exposed
to the intensely hot flames inside the heater.
Will your safety systems provide adequate control? If the pop-off valve opens, will water flood your
basement? If the fire goes out unexpectedly, what happens to the oil flow? Does it soak your carpets
with black oil or contaminate ground water supplies? What happens to the system if you have a
These safety issues are not trivial. Please deal with them competently and responsibly. Failure to do
so could result in your injury or death – worse, how would you feel if one or more of your family
members were injured or killed due to your negligence? What if you burn your house down?
The biggest problem is how to control the heat when heating water – particularly when using a
recirculating hot water heating system in your house. If you have too much fire, the water can boil.
Too little doesn't give you enough heat.
This is a serious problem when heating your home with hot water radiators as they need to be fed
water that is close to boiling to get adequate heat, but the water must never actually boil or you will
get a steam explosion. So the temperature range is very narrow and you really need to have some
sort of automatic regulation of the oil flow to hold a precise temperature.
My heater is designed to work manually, like a wood stove, where you keep an eye on it and adjust
the temperature yourself. This works just fine for heating a shop or garage where precise
temperature control is not an issue, you are heating only air, which can't explode, you are present in
the room most of the time, and you don't heat it 24 hours per day. But the situation is different when
you want to heat your home or water heater precisely and continuously.
Therefore, I DO NOT RECOMMEND using this type of heater for heating water.
If, despite my warnings, you insist on moving forward with your plan for hot water, I suggest that
you wrap many feet of copper tubing in a spiral around the inside of the heater to act as a heat
exchanger. The flames from the heater will bathe these coils and will heat the water within them. I
would use at least 3/4-inch tubing (2 cm), and larger is better.
Use a safety pop-off valve at both the inlet and the outlet of this tubing. The heat will make the
tubing weak and prone to sagging, so support it well.
You need to be sure to pump water through the copper coil at all times that the heater is running
hard. This will keep the copper relatively cool and strong. If you run the heater hard with no water
in the tubing, the copper may melt.
A water-only heater should be insulated on the outside to trap as much heat as possible inside the
heater. You can use fiberglass insulation for this purpose as it will handle a lot of heat before
melting and will not burn.
For safety, I strongly advise that you place your hot-water oil heater outside so that only the pipes
from it can reach inside your home. Use multiple pop-off valves where the pipes enter your home.
Surround the heater in a strong structure so that if you have a steam explosion it will be contained.
Wood stove conversions
Many readers wish to convert wood stoves to oil use. This should work well, although I have not
built one myself. Despite my requests, no readers have reported back to me to confirm their success.
A wood stove is not as good as a round water heater because the flames will not uniformly heat its
interior (assuming it is rectangular) and it is lower than a tall water heater tank. But it will look
nicer than a water heater tank so may be acceptable in your home.
You will need to completely block all air vents into the wood stove and install a vertical 4-inch air
pipe (10 cm) – this is essential for proper operation of my heater design. If you wish to install the
wood stove in your home, you will need to take some serious action to deal with the messiness of
an oil heater.
This would include running the air pipe outside so that when you overfire the heater it won't belch
smoke and fumes into your house, but ejects them outside instead. You will then need to use a
damper (a butterfly valve) since you won't be able to reach an external restrictor plate. You should
make the heater 100% airtight to prevent any smoke or soot from blowing out of leaks in the stove.
Good luck cleaning the flue without getting some soot in your house. Frankly, I don't think an oil
heater belongs in your home, but sometimes free heat makes us compromise.
Probably a better way to heat your home with an oil heater is to place it somewhere where its
messiness can be controlled. A good place might be found in the basement or outside in a small,
enclosed, and well-insulated structure. You could then blow air over the heater and through ducts in
the house. Since most homes have forced-air heating, this should be relatively easy to do.
To prevent ash and soot from blowing through the ducts and getting everywhere in the house, you
should install filters between the oil heater and the duct work leading to the house. You must also be
careful to make the heater airtight so you don't get any odor in the house if you have an overfired
Heating a greenhouse
Hundreds of these heaters have been built per my article at the Journey to Forever website. Many
have been used in greenhouses.
I designed the heater mainly for workshops and garages. It will work very well in a greenhouse, but
you will have to tend it. If you are willing and able to do so, you will be well-served by the heater
and save a lot of money on heating costs.
You should think of a waste oil heater as being much like a wood stove. That means that it requires
frequent attention, although not nearly as much as a wood stove. But you can't just set a thermostat
and ignore it for months like you would most types of commercial heaters.
It requires daily cleaning. It is very easy to clean, and can be cleaned in less than a minute, but you
must do so every day.
It is not operated by a thermostat. You will occasionally need to check its operation and adjust the
oil flow valve to get the heat output you want.
The oil-flow rate will not be reliable. The flow will change based on the ambient temperature
because oil changes its viscosity dramatically with temperature. So for a given valve setting, the oil
will flow faster if the ambient temperature increases, and it will flow slower as the temperature
cools. You will need to adjust the valve every few hours to compensate for this if you have large
temperature changes between night and day.
If you want to run it in a greenhouse where you only visit it once per day or so, you probably would
like to have an automatic heater control system.
The heater I actually use is self-cleaning and it operates under thermostatic control. It has safety
features so there is no possibility of an oil spill and I only have to clean it once a month. But such a
heater is much harder to build – beyond the ability of most DIYers. For details, see "Full
I strongly suggest that you find a reliable source of waste oil before you build the heater. You will
also need some way to collect it as most waste oil is to be found in tanks and you will have to pump
the oil into your container in some way.
My heater is very thrifty on oil use. But it will still use about 3 gallons per day (11 liters). So if you
use it regularly, you will burn several hundred gallons per year. I burn about 500 gallons (1,892
liters) per year up here in the Rocky Mountains where we have long winters. So oil collection is
something that will require your serious attention. Don't expect to take a 5-gallon gas can down to
your local auto repair shop and get oil.
Like a wood stove, an oil stove produces smoke, soot, and ash. Therefore, its operation is somewhat
dirty. You will need to clean the flue every 500 hours of operation. You can use a small garden
shovel to remove ash from the bottom of the stove every month or so. When I clean the burner, I
have a pair of heavy rubber gloves that I keep in my ash bucket. I put these on to keep my hands
clean when I handle the burner.
My heater will put out an awful lot of heat. My shop is poorly insulated, yet the heater has no
trouble holding a room temperature of 100 degrees F (38 degrees C), when the outside temperature
is -20 degrees (-29 degrees C). That's a 120-degree temperature gradient (67-degree C) in what is
essentially a 4-car garage. That's a lot of heat.
But if you want more heat, it should be a simple matter to scale up the heater to a larger size. The
main limitation on heat is the flue. You'll need to increase the flue from 6 inches to 8 inches. You'll
also need a larger heater shell, a larger burner, a 6-inch air pipe, and a larger oil-flow valve.
Alternatively, you could use two heaters.
For the convenience of my readers, I now manufacture machined, conical, aluminum burners and
have them in stock. They cost $50. Shipping adds $5 for US domestic or $15 for international
I also have precision needle valves in stock. They are also $50 each, but shipping is free if included
with a burner. Shipping for a needle valve without a burner is $5.
Photo #22 shows this valve. Orient it vertically so you can
watch the drops fall from the nozzle.
I accept all forms of payment including check, money orders,
major credit cards, and PayPal. If you wish to send a check or
money order, my address is:
12054 Deer Trail Road
Conifer, CO 80433
If you wish to use a credit card, I'll need its account number,
expiration date and the card's billing address. If you wish to use Photo #22
PayPal, send payment to my e-mail address:
I generally ship the day following receipt of payment by Priority Mail.
Waste oil filters can be obtained from Dymatic, Inc., in Chicago. They have a suitable filter made
by Lenz, part number DH-1000-100. Their price is $49.95. I purchased my waste oil filter/water-
separator on eBay. It is made by COMBU, model number 70101. It is a 100-micron filter using a
cleanable metal screen rather than a paper element. The Lenz filter also uses a metal screen. The
COMBU filter is made in Italy, but there is an American dealer who carries them:
2001 S. 21st St.
Parsons, KS 67357