50 Tips for Saving Energy_refrigeration_web_r2

5050Low- and
No-Cost Tips
for Saving Energy
Industrial Refrigeration Energy Efficiency

© Copyright 20132 50 LOW- AND NO-COST TIPS FOR SAVING ENERGY: REFRIGERATION SYSTEM
If you pay the power bill at an industrial cold storage or food distribution center,
you know that refrigeration systems never stop consuming energy. As the largest
electrical energy consumers in cold storage or distribution facilities,
refrigeration systems should be a major savings target for spend-weary
corporations. Yet, in today's economic climate where budgets for capital projects
are small or non-existent, finding ways
to reduce your energy spend can be a
challenge.
The solution? Driving energy savings
through low- or no-cost operations
and maintenance activities. This eBook
offers FIFTY of the best opportunities for
achieving savings at little or no capital cost.
LOW- AND NO-COST SOLUTIONS THAT
INCREASE ENERGY EFFICIENCY
CONTENTS
1 Evaporator Opportunities
2 Compressor Opportunities
3 Evaporative Condenser Opportunities
4 Control System Opportunities
5 System Opportunities
6 Systems Influencing Refrigeration Load
SAFETY ALERT
The improper execution of the activities outlined in this eBook could result in poor
system performance, property damage, product quality issues, and serious bodily harm.
Put safety first. Get qualified third-party contractors or certified refrigeration operators
to implement the O&M actions in this guide, if your staff does not have the expertise.

1 Cleaning Coils – Evaporator coils should be regularly inspected and cleaned, particularly in docks
or production areas where dirt, cardboard dust, rubber tire particulate, and other contaminants are
common. Dirty coils may prevent a space from achieving temperature, force the system to run at
lower suction pressure, or hinder evaporator fan cycling or variable frequency drive (VFD) control
effectiveness. Dirty coils may not defrost well.
2 Tune Overfeed Rates – Systems with liquid recirculation (also called overfeed) design utilize
hand expansion valves to meter liquid refrigerant at a 3:1 or 4:1 overfeed rate. If the valve is
throttled too low, the coil will starve. If the valve is too open, the evaporator will brine. Adjust the
valve to provide the maximum air temperature drop across the coil.
3 Adjust Defrost Relief Regulators – Hot gas defrost is often managed with a gas relief
regulator at the coil exit to maintain a target pressure within the coil during the hot gas phase of the
cycle. If this regulator is set too low, the defrost will be too long (due to low refrigerant temperature)
and the regulator will freely allow gas to pass and load the engine room. If the regulator is set too
high, this may force the system’s minimum condensing pressure to be set higher, or cause steaming
during defrost. A reasonable target is 70-75 pounds per square inch gauge (psig) for ammonia
systems.
4 Adjust Master Hot Gas Regulator – Some systems
utilize a master hot gas pressure regulator to maintain
consistent pressure in the main hot gas header serving the
coils. Pressure that is too high in the main header, results in
excessive coil temperature and increased false loading in the
engine room. The minimum system condensing pressure must
be set at least 5-10 psig above the master regulator set point.
A reasonable target pressure for the master regulator is 85-90
psig for ammonia systems.
Evaporator Opportunities
t i p
A service provider should ensure
coils are clean and clear of heavy
frost before tuning.

Evaporator Opportunities
5 Remove Oil – In most systems, any oil that migrates from the compressor eventually ends up
in low-pressure receivers or evaporator coils. Oil in evaporator coils hinders cooling, and makes it
extremely difficult to achieve a complete defrost at the bottom of the coil. Ice builds up and may
eventually bridge to the defrost pan. It is important to remove this oil.
6 Repair Valves and Regulators – It is important that hot gas solenoids fully close and do not
leak hot gas into the liquid or suction line. Also, regulators should fully close, as well as smoothly
and consistently maintain target pressures.
7 Remove Aging Ductwork – Older system designs included wooden or metal ductwork to
distribute air flow throughout a space. Unfortunately, this ductwork cannot be cleaned and may
also prevent cleaning the evaporator coil fans (usually centrifugal) and coil surface. Modifying or
removing this legacy ductwork can dramatically improve zone temperature management and system
efficiency.
8 Tuning Pressure Regulators – Some evaporator coils or process heat exchangers (e.g., water
or glycol chillers) are equipped with fixed or dual-pressure regulators. Ensure that the regulators are
set for the greatest temperature difference allowed by system limitations (such as freeze protection,
high humidity, etc.). Consult the original design engineer or contractor to determine the limits of the
application.
t i p
Differing frost patterns on valves
during a given mode of operation
indicates inefficiency.

9 Solve Current Limiting / Forced Unloading – Screw compressor microprocessor panels
usually include settings to prevent overloading of the motor. If the panel sees motor current driving
above nameplate or the service factor, the compressor will stop loading or even unload. This causes
the compressor to lose efficiency by running in an unloaded condition. This may force the control
system or operators to fire off another compressor to
supply capacity. Use a clamp-on current meter to ensure
that the current reading of the compressor microprocessor
is correct. Also ensure that the current limiting parameters
in the panel correctly match factory recommendations for
stop-load or force-unload settings. It is not uncommon for
current transformer (CT) multipliers to be in error or for
the incorrect current limiting parameters to be entered
into the controller.
10 Ensure Economizer Operation – Ensure that economizer ports function properly. The
economizer pipe should be cold to the touch when the system is operating. Most economizers
have a pressure regulator; ensure that the regulator is set to its factory recommended level. Most
microprocessor panels will disable economizer function below a prescribed slide valve position (e.g.,
75%) since economizer port gas is open to main suction pressure as the compressor unloads. Ensure
that this setting is correct. It is not uncommon for a failure on the microprocessor board, or a failed
economizer solenoid to prevent function altogether.
11 Auto VI Feature – Some screw compressors have automatic volume ratio controls. This matches
the compressor internal compression ratio to the external system pressures to prevent over or under
compression and loss of efficiency. Ensure the auto VI system is calibrated and operating correctly.
If an external control system is managing compressor VI, ensure the system is calibrated and
functioning properly.
t i p
Most modern screw compressors have a
microprocessor panel and control sensors,
both of which must be calibrated correctly
or else compressor performance can suffer.
COMPRESSOR Opportunities

Compressor Opportunities
12 Manual VI Feature – Other screw compressors may be equipped with a manually-adjustable
volume ratio feature. Read the factory operating manual to determine the proper VI setting.
13 Repair Shaft Seals – Repair any leaking compressor shaft seals, ESPECIALLY systems operating
in a vacuum. Air entering the system will impact condensing pressure, place a burden on the purging
system, and introduce water into the refrigerant charge.
14 Avoid Excessively Low Cut-Out – If compressor cut-out suction pressure is set too low, a
compressor may not turn off under extremely low-load conditions. The compressor will simply pull
down to extremely low suction pressure and draw fully-unloaded power. If the compressor is set up
this way on purpose (e.g., it has problems starting, see below), resolve this issue.
15 Solve Starting Issues – If a compressor cannot reliably start and stop, it may be tempting to
operate it in an unloaded state to avoid the problem. Instead, resolve the issue that prevents reliable
starting, whether the issue is with the motor starter or controls. If the concern is excessive motor
restarts, consult with the compressor or motor manufacturer to determine the minimum allowable
anti-recycle time to allow the compressor to restart promptly and avoid system disruption.
t i p
Critical set points for
compressors include economizers,
pressure sensors, VFD settings,
current transducers, and
compression ration settings.

16 Unplug Spray Nozzles – Regularly inspect evaporative condenser spray nozzles to ensure
nozzles are not plugged.
17 Water Treatment – It is critical that water be treated for
solids and biological content. It only takes a small amount of
buildup on condenser tubes to dramatically reduce capacity
(e.g., 1/16” of calcium carbonate can reduce condenser
capacity by nearly 50%). Hold your water treatment
contractor accountable for system performance. This will
require regular inspection of condenser tubes.
18 Water Pressure – Although tempting, increased water pressure does not improve evaporative
condenser performance. Most condensers are designed with modest water pressure at the header,
perhaps 3-6 psi. Install a glycerin-filled 0-15 psig gauge in the condenser water distribution header
and throttle the condenser pump to deliver the correct pressure. If substantial throttling is required,
have the pump impeller trimmed to provide the proper amount of pressure for the application.
19 Clean Strainers – Regularly inspect and clean the condenser sump pump inlet strainer. A plugged
strainer will reduce condenser capacity and waste pump energy.
20 Adjust Sump Water Level – Ensure that condenser sump float level is correct and that water
level is not too low. Low water level can result in poor pump performance and water flow.
21 Plugged Fill or Drift Eliminators – Regularly clean fill material on induced draft condensers
and drift eliminators on most condensers. Otherwise, reduced air flow will impact condenser
performance.
22 Address Non-Condensables – Ensure the purger is working properly and that air is being
eliminated from the condenser. Do this by measuring pressure and temperature at the condenser to
verify the values correspond.
Evaporative Condenser
Opportunities
t i p
Good water treatment is critical to
avoiding scaling on the tubes that
causes a reduction in performance.

23 Tension Belts – Check condenser fan belt tension to ensure there is no slip. Slip will reduce air
flow and waste fan energy through the slip itself.
24 Address Recirculation or Bad Environment – Poor condenser configuration may result
in warm, moist exhaust air from one condenser being drawn into a neighboring condenser. Poor
rooftop layout may result in a boiler blow-down stack or process exhaust air stream placed near the
inlet to a condenser. In all cases, address the issue to relocate, raise, or otherwise reduce moist or
warm air entering the condenser.
25 Correct Poor Drift Eliminator Strap Configuration – To properly inspect condenser
performance, hold-down straps must be loosened to allow drift eliminators to be removed. In some
cases, these straps are configured so that they’re difficult or impossible to remove. Reorient, or
otherwise modify the strapping system to correct this issue.
26 Wet vs. Dry Operation – Evaporative condensers are inefficient when operated dry, particularly
when ambient temperatures are above 30-40°F. Ensure that condensers are properly winterized
(sump heaters, heat trace, etc.) so they safely operate wet down to 25-30°F ambient.
27 Sump Heaters – Ensure any electric sump heaters (often 10 kW, 20 kW or more) are functioning
properly. Failed or incorrectly adjusted thermostats can result in inappropriate energy use by the
heaters, and heating of the water that elevates discharge pressure.
t i p
Proper maintenance helps avoid
the top threats to condenser
performance: non-condensable
gases, scale on the tube bundle,
and poor spray-water dispersion.
EvaporaTIVE CONDENSER Opportunities

28 Zone or Process Temperatures – Warehouse cooler or freezer temperatures should be set at
an appropriate value as determined by product or customer requirements. Product, glycol, or other
process temperatures should not be set lower than required. This may seem obvious, but systems
are often set to maintain lower temperatures than necessary.
29 Suction Pressure – Raise system suction pressure to the
highest allowable value (which is usually dictated by the
worst-case temperature zone or process load). Note that this
will affect evaporator fan cycling or VFD control, so some
optimization may be in order.
30 Condensing Pressure – Operate the system at the lowest
allowable minimum condensing pressure set point. If a
system can be operated as low as 90-100 psig (for ammonia)
without problems, this is a reasonable target. Note that
defrost, freezer floor heat, liquid injection performance, and compressor oil carryover are potential
barriers to reduced minimum condensing pressure. Discuss possible limitations with the equipment
manufacturer, refrigeration contractor, and system operators.
31 Condenser Wet Bulb Approach – If the control system offers a condenser wet bulb approach
control feature, activate it and target an approach in the 12-15 degree range. The optimum value
may require experimentation. This feature ensures an appropriate balance of condenser capacity
relative to refrigeration load and compressor operation.
32 Evaporator Fan Cycling – If the control system offers an evaporator fan cycling feature,
activate it. In some cases, a swirl feature will operate the fans a minimum duty cycle to mix room air.
Set up the swirl feature for the minimum required. If the control system has separate cut out and cut
in set points for liquid solenoids and fans, energy savings is maximized when the cut in and cut out
set point is the same for the solenoid and fan control.
Control System Opportunities
t i p
Fine-tuning control systems and using
them to take advantage of demand-
response programs or varying utility
rate schedules – can be a considerable
source of energy and cost savings.

33 Condenser Staging – Operate the most efficient condenser in the lead list first. Generally, the
most efficient condensers are axial fan units with integral sumps. Centrifugals are less efficient,
as are those with remote sump pumps or limitations to operation during frigid weather. Evaporative
condensers are most efficient when wet with air flow at mid-range fan speeds. Avoid turning all
system pumps on first, and then starting to add fans. Turn on a condenser pump, then the fans,
then the next condenser pump, then fans, etc. The goal is wet with air movement for the greatest
efficiency.
34 Defrost Schedule – If the control system only offers a fixed
defrost schedule, experiment with the number of defrosts per
day to minimize defrost count. Do not let frost build up so
much that it becomes difficult to achieve a full, clean defrost.
There is no rule of thumb for defrost interval – many coils can
operate 8-16 hours or more between defrosts. In dry climates,
it is not uncommon for evaporators to be defrosted only once
or twice a week.
35 Defrost Initiation – If the control system offers a liquid run-time feature or frost sensors, use this
feature to initiate defrost only when necessary.
36 Defrost Pump Down – Ensure that all liquid is fully boiled out of the evaporator coil before hot
gas is introduced. Watch a coil closely during a test pump down and measure fin temperature with
a laser thermometer, or watch air temperature drop to determine when a coil is completely dry. This
may require 30-60 minutes for a frosted coil or one with VFD control operating at reduced speed.
37 Defrost Hot Gas Duration – Most evaporator coils should be able to clear all frost with 10-20
minutes of hot gas. If you find a coil needing 45-60, or more minutes of hot gas to clear all frost,
there is probably something wrong that should be addressed (e.g., hot gas regulator pressure,
inadequate pump down, etc.).
38 Transducer Sensor Calibration – Use an ice bath to calibrate key zone or process
temperature sensors. Calibration pressure gauges ensure that the pressure transducers, used by
a central control system, are properly calibrated. You may need to adjust offsets in the control
system or even replace a failed pressure transducer. For compressors operating off their local
microprocessor panels, calibrating control pressure transducers is critical (particularly suction).
t i p
Make sure the winterizing heat trace
and sump heaters are functioning so the
system performs well in frigid weather.

39 Poor Ambient Probe Location – If a control system ambient temperature probe is located in
direct sun, the probe will not read properly. This is particularly important when utilizing a condenser
wet bulb strategy.
40 Frigid Weather Condenser Strategies – Many central control systems can turn off condenser
water pumps (or drain condenser sumps) during frigid weather for freeze protection. It is important
that these set points be set at reasonable values to minimize dry operation of the condensers.
41 Tune Internal VFD Parameters – For evaporator and
condenser fans, the most efficient VFD configuration is
typically a low carrier frequency and a “square” or “variable”
torque curve. There may also be energy-saving features or
settings that can improve efficiency. The best method is to
measure VFD input power with an appropriate power meter
and experiment with these parameters to obtain the
minimum power.
42 Optimum Evaporator VFD Strategies – In general,
evaporator fan VFDs can be operated with a minimum speed in the range of 40-50%. There is little
additional savings from going slower. Limiting evaporator maximum speed to 90 or 95% can add
savings with very little impact on net evaporator capacity. Liquid feed or pressure regulators should
stay at full capacity until the fan VFDs are at minimum speed. Simultaneous speed control will save
more energy than sequential ramping of speed when there are multiple coils in the zone.
43 Optimum Compressor VFD Strategies – Compressor minimum speed is dictated by
compressor or motor limitations, typically in the range of 20-50%. Consult the manufacturer for
proper settings. In nearly all cases, the compressor micro-processor manages the VFD and slide
valve. Speed should be reduced first. Once at minimum speed, then the slide valve can be closed.
Avoid simultaneous adjustment of speed and slide.
44 Optimum Condenser VFD Strategies – Implement pump and fan staging, minimum and
maximum fan speeds to target the general strategy of “wet with air at mid-range speeds.”
Mid-range can be defined as 30 to 80% speed. Once all condensers are online, fan speed can be
allowed to rise to 100%.
t i p
All VFDs have internal parameters such
as carrier frequency, torque curves,
minimum and maximum speeds. It is vital
that VFDs do exactly what the control
system tells them to.

45 Purger Performance – Ensure that the purger is operating properly. The purger counter should
show a reasonable level of purging, but note that no system is perfect. There are control fuses,
check valves or solenoids that can fail and prevent proper operation.
46 Water in the System – Regularly test the system refrigerant for excessive water content.
Excessive water will change the properties of the refrigerant and substantially reduce system
performance and efficiency.
47 Pump Drum Tuning – A gas pressure system (also called a Phillips or Pumper Drum System) has
a number of critical pressure control regulators. Flash gas from a controlled-pressure receiver (CPR) or
low pressure vessels should be properly routed to an appropriate suction (or economizer ports). Any
hot gas supply regulators should be carefully adjusted to prevent false loading of the system. Liquid
transfer units (LTUs) that utilize hot gas for dumping and liquid transfer should be carefully set up to
avoid false loading of the system. Set CPR pressure to the lowest allowable value to maximize sub-
cooling and prevent the CPR from acting as a barrier to minimum allowable condensing pressure.
48 Repair Faulty or Leaking Float Drainers – Liquid float drainers may be installed on main hot
gas defrost headers, individual evaporator defrost relief, under-floor glycol heat exchangers, or other
applications. If the float drainer is leaking hot gas, it will false load the system. Ensure that all liquid
drainers are functioning properly.
System Opportunities
t i p
Water in a refrigeration system
dilutes and impacts the boiling
point of the system’s ammonia.
A water removal system or
hybrid air/water purger should be
installed to maximize efficiency.

49 Door Performance – Dock, cooler, or freezer door
performance directly impacts refrigeration load and defrost
requirements. Door seals, door defrost heaters, sensors,
closing delays, and other characteristics are extremely
important to minimizing refrigeration load. If re-circulatory
air doors are used, proper control of air heaters (electric or
hot gas), adjustment of air flow directional vanes, and clean
return air screens or grates are key to efficiency.
50 Lighting Performance – Warehouse lighting controls,
including motion sensors, bi-level control on high-intensity
discharge lighting, manual or time clock controls all directly
impact refrigeration load. Every watt of light fixture power
ends up as refrigeration load in the space.
Systems Influencing
Refrigeration Load
t i p
Install motion controls and
set sensor time delays to the
minimum allowable delay for
facility use patterns, safety, and
manufacturer specifications.
t i p
Ensure that freezer under-floor
heating systems are set to
the minimum required ground
temperature to prevent heaving.
This should be carefully considered
and implemented.

Points to Consider
Think about the following as you pursue low- and no-cost efficiency gains:
Be willing to experiment while maintaining system stability and reliability. Every refrigeration system
is unique and displays its own quirks and character. For this reason, each system must be poked,
prodded, and otherwise forced to show its limitations and capabilities.
It is important to remember that functional does not imply efficient.
In most cases, a well-tuned and properly maintained system is more efficient.
A small group of people dictates the energy use for the refrigeration system. These people are critical
to reducing energy use.
You must understand more than how a refrigeration system operates. It is important to understand
what drives the energy use for each component or system in a way that allows you to make wise
decisions regarding configuration, set points, and strategies. Consider a taking class that focuses on
efficiency to improve your understanding and skill set.
It is possible that there are misconceptions that have been passed on by other system operators,
contractors, or vendors that are limiting efficiency of the system. Ask questions, do research, and
talk to experts. Trust but verify.
Design conditions are just that – information used to select components and configure the system.
Often, design conditions are not intended for day-to-day operation, particularly when pursuing
efficiency gains. Avoid clinging to these values unless there is a strong, reasonable, or justified case.
Some system inefficiencies or barriers can only be seen during certain seasons. For example, high
condensing pressure may only manifest during the summer whereas limits to system minimum
allowable condensing pressure may only be addressed during winter. If you utilize a third-party
contractor to operate or maintain your system, the contractor must be involved in pursuit of energy
efficiency. Implement processes, goals, or requirements to ensure alignment and accountability.

123 NE 3rd Ave, Suite 400
Portland, OR 97232
503.287.8488 main
503.287.8788 fax
INDUSTRIAL STRENGTH ENERGY EFFICIENCY
TALK TO CASCADE ENERGY TODAY! 866.321.4573
20 years
Deep, hands-on technical
expertise over a 20-year span.
2,000 projects
Analyzed and implemented more
than 2,000 energy efficiency
projects.
350 sites
Monitor energy performance at
over 350 industrial sites.
250 facilities
On-site tune-up and retro-
commissioning at over 250
industrial facilities.
Cascade Energy provides corporations and utilities with the industrial strength
expertise needed to realize their energy efficiency potential. With a full
complement of services and engineering know-how based on 20 years of
hands-on experience, Cascade has a proven track record of reducing industrial
energy consumption and costs.
cascadeenergy.com energysensei.com info@cascadeenergy.com
Industry Expertise
• Refrigerated storage
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• High technology
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System Expertise
• Refrigeration
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EBOOK-003-2 REV 1-OCT-2013

50 Tips for Saving Energy_refrigeration_web_r2

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