central heating 3

1. Central Heating

2. Types of central-heating system
• As with cold and hot water systems there are many
different types of central heating system out in the
workplace.
• Some which could be decades old still working but in
need of either refurbishment or maintenance
• Some systems need to be extended or have controls
added to make them compliant with the latest Building
Regulations
• Like TRV (Thermostatic Radiator Valves), mid position
valves, programmers, cylinder and room thermostats
for total control of heat and efficiency

3. The one pipe system

4. One pipe system

6. Two pipe system semi gravity
• This was a popular choice of system particularly in the
1970s. It is no longer permitted on new properties
(other than with solid-fuel boilers) without additional
controls being installed.
• Nor do they meet the requirements of the Building
Regulations for extension or boiler replacements to
existing oil- or gas-fired systems.
• In a two-pipe system, water is pumped around both
the circuit and the radiators.
• This improves the speed with which radiators heat up.
The system can easily be balanced by adjusting the lock
shield valve on each radiator.

7. Building Regulations and central-heating
• The Building Regulations 2000 deals with the
conservation of fuel and power
• Approved Document L1: Conservation of fuel and
power.
• This document sets out the requirements for all
central heating installations in domestic dwellings

8. Fully pumped systems Y - plan

9. Fully pumped systems
• In this system, the hot water and the heating
circuits are operated completely by the pump.
• Installations are controlled by motorised
valves.
• There are a number of system designs
incorporating two-port zone valves or three-
port valves (two-position and mid-position)
that meet the requirements of the Building
Regulations Approved Document L1.

10. S-plan ( zone valves )

11. Feed and expansion cistern
• As you have seen from the diagrams in this chapter, the
feed and expansion (F&E) cistern is used on all open-
vented central-heating systems.
• While the cistern allows the system to be filled up, its
main purpose is to allow water in the system to
expand. The water level should therefore be set low in
the cistern when filling the system.
• The cold feed to the system in an average domestic
property is usually 15 mm minimum, and this pipe
should not include any valves.
• This is to ensure that, in the event of overheating,
there is a constant supply of cooler water to the system
to prevent the dangerous condition of boiling.
• The servicing valve to the system should be located on
the cold-water inlet pipework to the cistern

12. Feed & Expansion cisterns
• The F&E cistern is
located at the highest
point in the
system, and it must
not be affected by the
position and head of
the circulating pump

13. Pump positions

14. Primary open safety vent
• In a fully pumped
system, this should
usually rise to a
minimum height of 450
mm above the water
level in the F&E cistern
to allow for any
pressure-surge effects
created by the pump

15. Air separators
• The purpose of the air
separator is to enable the
cold feed and vent pipe to
be joined closely together
into a correct layout to
serve the system.
• The grouping of the
connections causes
turbulence of water flow in
the separator, which in turn
removes air from the
system.
• This reduces noise in the
system and lowers the risk
of corrosion

16. • Here is a common
picture of a air
separator
• The connections are
normally
• to cold feed
• to vent pipe
• to boiler flow

17. Heat emitters
• Just another name for a
radiator, well no there
are many different heat
emitters from fan
assisted to your standard
panel radiator here are
just a few
• Kick space or plinth type

18. • The standard panel
radiator which
depending on
manufacturer can have
several different
features as to sizing and
shape

19. Some of the different types of radiator

20. • A traditional type
towel rail with inset
column radiator
• The radiator supplies
a small amount of
heat while the rail
dries the towels

21. Modern type towel heaters
• A modern type towel
may look decorative,
but some rails are there
only to dry towels.
• They hardly throw any
background heat into
the room, but are quite
popular

22. How to fit them
• The standard radiator is
fitted approx 150mm to
175mm from the floor,
this is to allow for air
flow around the
radiator.
• However if required
because of high
skirting's or other
obstacles they can be
fitted higher

23. Radiator brackets
• A number of brackets and
fixing
• styles are available, and are
usually provided with the
radiator.
• The bracket shown has
deep hanging slots and
corresponding lug positions.
• These provide greater
stability. Plastic inserts are
used to seat the radiator
precisely and help to
minimise expansion and
contraction noises

24. Radiator valves
• There is a wide selection
of valves available from
manufacturers.
• Building Regulations
require thermostatic
radiator valves (TRVs) to
be installed on new
systems or for there to be
some other means of
controlling an individual
room’s temperature

25. Wheel-head radiator valves
• These enable the
occupier of the building
to control the
temperature of the
radiator manually by
turning it on or off.
• Rotating the plastic
‘wheel head’
anticlockwise will raise
the spindle through the
body of the valve, lifting
the valve and opening the
flow to the radiator.

26. Wheel-head radiator valves
• This is the inside of a
radiator valve
• Most of them have similar
internal workings , but
some valves can withstand
higher pressures, or are
designed to fit the
customers needs angled or
straight or thermostatic

27. • Traditional boilers
• boilers with cast-iron,
high-alloy steel, copper
or aluminium heat
exchangers
• system boilers.

28. • All boilers can be floor
standing or wall-mounted, and
are usually designed to fit in
with kitchen unit installations.
• Gas-fi red back boilers are also
available; these are concealed
in a chimney opening at the
back of a gas fire.
• Traditional or regular boilers
supply hot water indirectly via
a domestic hot-water storage
cylinder, which is usually sited
at first-floor level

29. Condensing boilers
• The condensing boiler has to include a fan to make
the process work, and the heat exchanger is larger
than that in non-condensing boilers.
• The boiler is able to extract more heat from the
combustion process than traditional boilers,
making it more efficient.
• As the flue gases are cooled, the water vapour they
contain turns to liquid (condensates), which has to
be drained from the boiler to a drain or soakaway.

30. • Condensing Combi
boilers now are so
efficient compared to
old boilers, that from
2004 any new boiler
fitted had to be
condensing

31. Time switch
• A time switch is an
electrical switch
operated by a clock to
control either space
heating or hot water, or
both together
• Some are programmer
thermostat and have
multi functional
displays, and some are
even wireless

32. Automatic bypass valves
• These are mechanical devices
used to make sure water can flow
through the boiler to maintain a
minimum water-flow rate should
a system using zone valves or
TRVs become closed.
• Once set, the valve opens
automatically as the TRVs or zone
valves close and the system
pressure goes over the pre-set
limit.
• Use of the bypass valve reduces
system noise and increases pump
life by preventing it working
against a ‘dead head

33. • An auto bypass open to
stop damage to the
pump on the system
• It can however become
damaged with system
debris which makes the
valve vibrate and
normally a high pitched
buzz can be heard
throughout the system

34. Automatic air vents
• These are used on central-
heating systems in order to
remove air from the system
automatically.
• A vacuum break on the
bottom of the valve
prevents an air lock forming
and encourages air to be
released from the water.
• Vents should always be
installed on the positive
side of the system and
positioned where air is
likely to get trapped

35. Motorised valves
• Three-port diverter valve
• This can only give hot
water or heating
• The ports on the valve are
• AB the inlet from the flow
• A which is the out let to
the heating
• B which is the outlet to
the hot water cylinder
( B for Bath )

36. Zone valve
• A motorised valve
which opens and closes
when told can be used
any where on central
heating required or for
domestic hot water
applications, usually
though on larger
building

37. Mid position three port valve
• This valve looks very
similar to the three port
valve, and it is.
• The difference is it can
do central heating and
hot water both at the
same time, the valve
goes to a mid position
to do this

38. Junction box or Wiring centre
• These provide the connections
between the electrical system
components and the mains
electricity supply.
• Most manufacturers supply their
controls in packs, and these can
include a wiring centre which is
designed to simplify the wiring
of a particular system pack.
• Packs include control valves,
programmers and thermostats.
All the terminal connections are
clearly marked, and full
instructions are included with
the wiring centre

39. Soundness testing of central-heating
pipework systems
• visual inspections
• Pressure testing
• Cold flushing the system
• final checks
• Hot flushing of pipework
• anti-corrosion procedures

40. Decommissioning of central-heating systems
• Isolate the system • Make sure the electrical supply to the
heating system is isolated. Turn off the
boiler.
• Remove the fuse from the spur outlet
to the wiring centre or junction box for
the controls. Advise the customer of
what you are doing and not to touch
the controls.
• Only work on the system when the
water has cooled.
• If you speak to the customer
beforehand to arrange the job, it is a
good idea to ask them to turn off the
system so that it is cold when you get
there

41. Close all outlets
• Turn off the service
valve to the F&E cistern;
close any automatic air
vents.
• The open vent pipe and
cold feed now need
plugging –
manufacturer devices
are available, to carry
this out

42. Draining down the radiator
• This is carried out by isolating both radiator valves and the
loosening of the union nut on the radiator valve to be
replaced.
• Catch the water from the radiator in a small bowl, and have
a bucket handy to empty the bowl from time to time. Air
needs to be let in to the radiator through its air vent to
ensure that the water in the radiator fully drains out.

43. Filling a heating system
• There are a couple of
different ways of filling a
heating system
• With the open vent
system the water fills its
self, but air must be
removed from radiators
with a key
• However sometimes air
locks can happen on
poorly designed systems

44. Sealed systems
• With sealed systems such as
combi’s most of the time this
is done via a filling loop, it
can be fitted external to the
boiler, or inside of the boiler
as per the manufacturer.
• The normal operating
pressure of a sealed system
is about 1 to 1.5 bar
• The rads are bled the same
as before to remove any air,
inside the boiler

45. • The radiators are bled the
same as before to remove
any air.
• inside the boiler an AAV
( automatic air vent )
removes the air from the
boiler, then the pressure
is checked on the gauge
cold against
manufacturers
instructions

46. Finishing touches
• When the job is finished a
fully fitted central heating
system complete with boiler
and all controls are complete,
this should last the customer
for years,
• At this point the instructions
and how to use the system
should be shown to the
customer, and Benchmark left
filled in by the installer for the
customer

47. •Any Questions ?