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Click on the links below to view answers:
-
Where can I find
information on Emerson technical training?
-
How much oil is in a hermetic compressor and what is a
complete recharge?
-
When should oil be added to a system because of line
length and how much when there is no sight glass in the
compressor?
-
There are many oil additives that claim to increase
compressor or system efficiency, others that neutralize
acid or find leaks. What oil additives does Emerson
approve?
-
Does Emerson limit the length of line runs or vertical
risers?
-
How can I tell if the compressor is operating properly?
-
A single-phase unit dims the customer’s lights when it
starts. What can be done to remedy this?
-
Can a universal
capacitor and relay be used with Copeland®
compressors?
-
Will replacing the compressor solve a unit’s noise
problem?
-
Are pressure relief valves required to be used on
remanufactured compressors purchased from Emerson
Wholesalers?
-
What do I do if the oil pressure safety trips?
-
What would cause a compressor to run in a rapid cycling
mode?
-
What would cause my compressor to overheat?
-
What needs to be checked when an erratic oil pressure
control trips?
-
What needs to be checked when a compressor trips on
protector?
-
How do I know if a compressor is operating to capacity?
-
What is considered good oil pressure?
-
What are the proper methods to determine operating
superheat, sub-cooling and net oil pressures?
-
Which starting
components should be used with Emerson's new single-phase welded models?
-
Should a suction line filter drier be installed before
or after an accumulator?
-
Can I use a receiver on a cap tube system?
-
Can I directly replace R-12 with R-134a refrigerant?
-
Is it acceptable to use R-404A and AB?
-
Why do refrigeration manufacturers recommend only 80% to
90% of original system charge when retrofitting to some
HFCs?
-
Can I purchase pistons, rods, bearings and cranks?
-
How can I dispose of my failed compressor?
If you do not find an answer to your question, please
contact us
so we can help you.
Q1. Where can I find
information on Emerson technical training?
ANSWER: Visit the
training
page for information on Emerson's renowned Compressor
Operation & Service Seminars (COSS), as well as order forms
for videos, workbooks and literature.
Top
Q2. How much oil is in a hermetic
compressor and what is a complete recharge?
ANSWER: The amount of oil in fluid ounces is on the
nameplate in the box marked oil. A complete recharge
is four fluid ounces less than this amount since some of the
oil remains in the compressor after draining.
For more information on oil used in Copeland®
compressors see
Online Product Information.
Top
Q3. When should oil be added to a
system because of line length and how much when there is no
sight glass in the compressor?
ANSWER: The answer depends more on the amount of
refrigerant in the system and the compressor’s oil pumping
rate than on the amount of tubing surface to be wetted. A rule of thumb is to multiply the amount of refrigerant in
the system by 2.2% and multiply this number by 16 fl.oz./lb.
Subtract from this result 10% of the fluid ounces shown on
the compressor nameplate and add the remaining amount to the
system. This means that most systems don’t need
additional oil unless the refrigerant charge exceeds 35
pounds. Example: System charge is 50 lbs., compressor oil
charge from nameplate is 108 fl. oz. 50 lbs. x .022 x 16
fl.oz./lb. - (108 fl. oz. x 0.10) = 6.8 fl.oz. of oil to be
added.
For more information on a related oil management topic see
Online Product Information.
Top
Q4. There are many oil additives
that claim to increase compressor or system efficiency,
others that neutralize acid or find leaks. What oil
additives does Emerson approve?
ANSWER: The long-term effect of chemical additives
on refrigerants and materials used in the compressor are not
known without time-consuming, rigorous laboratory tests. The use of most of these additives is strongly discouraged
by Emerson and may result in voiding the compressor
warranty. Application Engineering Bulletin 17-1282
states
Emerson's
position on additives. An exception is the fluorescent
leak detection dye, AR-GLO®, made by Spectronics
Corporation, which can be used in systems with R-22 and
mineral oil in accordance with its instructions.
For more information on this topic see
Online Product Information.
Top
Q5. Does
Emerson
limit the length of line runs or vertical risers?
ANSWER: Since
Emerson Climate Technologies
is a component supplier we lack the field experience to
adequately answer piping questions such as this. We
would recommend following the system Original Equipment
Manufacturer's (OEM) guidelines, if available. Where
such information is not available, we would recommend using
standard ASHRAE piping guidelines or the tables found in
Emerson Climate Technologies'
refrigeration manuals AE-101 through 105. These are
available through a Emerson Wholesaler for a
nominal fee.
For more information on a related topic see
Online Product Information.
Top
Q6. How can I tell if the compressor
is operating properly?
ANSWER: The
best way to determine if a compressor is pumping properly is
with a set of gages, an amp meter and the compressor
specification sheet. Measure the operating discharge and
suction pressure as well as the amperage. Using the
compressor curve sheet, found on
Emerson Climate Technologies 's
Online Product Information
database, compare the amperage reading at the measured
pressures. Because of voltage variations and
measurement inaccuracies the measured amperage should
compare to the actual curve sheet values within +/- 15%. Never check compressor operation by closing the suction
valve to see how low the suction will go. This might
actually cause damage to the compressor because of heat
build up.
Top
Q7. A single-phase unit dims the
customer’s lights when it starts. What can be done to remedy
this?
ANSWER: The simplest device to reduce light dimming
caused by voltage droop while the compressor is starting is
to add a start capacitor and relay. The capacitor and
relay will reduce the amount of time the compressor is in
locked rotor and thus reduces the amount of time the bulbs
dim to a tolerable flicker.
For more information on this topic see
Scroll Start Components.
Top
Q8. Can a universal capacitor and
relay be used with Copeland®
compressors?
ANSWER: The only universal start assist device
approved for Copeland® single-phase compressors
is a PTCR (Positive
Temperature
Coefficient Resistor) device with a resistance
as low as 12.5 ohms or higher. These devices are made by
various manufacturers and are applied parallel to the run
capacitor. They are approved only as low volt start
assist with piston compressors in systems where the
refrigerant pressure equalizes or scroll bearing units. All other applications must use the specified Copeland® start capacitor and relay combination.
For more information on this topic see
Scroll
Start Components
and
Compressor
Start Components.
Top
Q9. Will replacing the compressor solve a unit’s noise
problem?
ANSWER: In many cases, replacing the compressor will
not resolve the sound issue and it is recommended that
different possible noise sources be explored before a
compressor exchange is considered. The noise radiated
by A/C systems can be generated by:
-
Compressor noise as an airborne sound
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Structural vibration of system’s components such as
refrigerant pipes, panels etc.
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Outdoor/indoor fan
Because of the interaction between these sources of noise,
it is sometimes difficult to pinpoint the origins of noise
using the ear only. In general, the compressor is not
the principal noise generator if the noise is heard only
indoors or if the noise is still present when only the fan
is running.
For more information on this topic see
Scroll Sound Enclosures.
Top
Q10. Are pressure relief valves
required to be used on remanufactured compressors purchased
from Emerson Wholesalers?
ANSWER: Any remanufactured semi-hermetic Copeland®
compressor (with the exception of 2Ds, 6Ds, and 8Ds) must
have a low side pressure relief valve (P/N 998-0051-02)
installed and set to a maximum of 375 psig if the compressor
will be used with any of the R-502 replacement refrigerants
approved by
Emerson. While these compressors were originally built to
meet industry accepted design safety factors for R-502, they
may not meet these factors with the new higher-pressure
refrigerants. All new Copeland®
semi-hermetic
compressor models - those manufactured since January 1, 1994
- meet the design safety factors for these new
refrigerants.
Top
Q11. What do I do if the oil pressure safety trips?
ANSWER: If the oil pressure safety trips, perform the
following analysis:
-
Check the sight glass for the proper oil level or
foaming. If there is insufficient oil in the compressor,
loss of oil pressure will occur. Foaming oil will
also result in low oil pressure.
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Low oil level is usually caused by inadequate return of
oil from the system. The refrigerant piping,
accumulator, oil reservoir, evaporator superheats,
defrost scheme and oil floats should be reviewed.
-
Foaming in the sight glass is an indication that liquid
refrigerant may be present. Liquid can return to
the crankcase by migration during long off cycles or in
large gusts when rapid system changes occur, as seen
during defrost. Incorrect expansion valve settings are
typically a cause. A crankcase heater or suction
accumulator may be needed.
Top
Q12. What would cause a compressor
to run in a rapid cycling mode?
ANSWER: Possible causes include:
-
Compressor oversized for load
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The "cycle on" and "cycle off" range of low pressure
control is set too close
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Undersized evaporator/suction line piping
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A leak in liquid line solenoid valve
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Oil float feeding erratically
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The compressor shows a high to low internal leak
Top
Q13. What would cause my compressor
to overheat?
ANSWER: Overheating problems occur when oil in a
compressor is heated to the point where it loses its ability
to lubricate. If the heat is high enough, the oil
breaks down chemically. Major reasons for
overheating due to discharge temperatures are:
Low suction pressure is normally the result of incorrect
pressure switch settings, pressure drop in suction line,
light load operating conditions or restricted evaporator
coils.
High condensing pressures can be caused by inadequate
airflow through the condenser, undersized discharge
line/condenser, and overcharge of refrigerant or
noncondensables in the system.
High-pressure ratios are a combination of low suction
pressures and high condensing pressures. If the compressor
is operated within the manufacturer guidelines, this
condition will not cause a problem.
Emerson Climate Technologies
recommends monitoring discharge line temperatures to
determine if the compressor is in a danger zone of
overheating. Generally, discharge line temperature of 225ºF
(107.2oC) and below will insure the compressor of
a long life.
Top
Q14. What needs to be checked when
an erratic oil pressure control trips?
ANSWER:
First, we must recognize that there is no such thing as a
nuisance oil control trip.
The tripped control is warning you of an existing problem.
The system should not be reset until you have looked in
the sight glass and recorded the level.
-
If the oil is below the glass, the system should be
checked for leaks or oil logging.
Investigate for the oil return problem.
This could be corrected by longer or more defrost
cycles, reducing short cycling, preventing low
refrigerant charge, eliminating piping problems, etc.
If it is determined that oil should be added it
must be removed once the problem is remedied.
-
If the oil is above the glass, the system should be
checked for the possibility of refrigerant diluting the
oil.
Liquid refrigerant floodback could be identified by
absence of superheat at the compressor.
It would be advisable to separate the refrigerant
from the oil by heating the oil with a crankcase heater
a few hours before starting or by jogging the compressor
(quick start/stop of the compressor several times) until
the foaming is controlled.
Remember the suction service valve should not
be closed while jogging the compressor.
If the valve is closed the refrigerant and oil
could manage a more violent explosion (flooded start) as
there is less space for the initial start-up pressure to
be pulled from.
-
If the oil level is in the sight glass, the oil may be
checked if it is too hot.
Identify this by checking the temperature six
inches out on the discharge line.
The maximum is 225°F
(107.2oC) at this distance.
Any higher temperatures could mean that the cylinder
temperature is above 300°F (148.9oC) and it could cause oil control trips.
If the oil is foaming excessively it may have
refrigerant dilution and may be identified as a
floodback problem.
On refrigerant cooled semi-hermetic compressors, the
problem could be an over-pressurized crankcase.
The root of this problem is overheat that causes
excessive crankcase pressures due to piston blow by at
low loads.
The problem may be found by attaching a gauge manifold
set to the crankcase and the suction.
With the compressor operating, start slowly front
seating the suction service valve.
Observation of the gages should show both falling
at an equal amount until the valve is fully front
seated.
The point at which the crankcase gauge stops
falling is proof that the crankcase blow by pressure
exceeds the venting.
Top
Q15. What needs to be checked when a
compressor trips on the protector?
ANSWER:
Emerson Climate Technologies
protectors are inherent, meaning they sense both temperature
and amperage.
If a protector trips, the system should be investigated for
the increased temperature or amperage problem.
Some causes could be charge shortage, high head
pressures, increased friction of moving parts, reduced
voltage, unbalanced voltages, shorted windings, etc.
Top
Q16. How do I know if a compressor
is operating to capacity?
ANSWER:
When selecting a compressor the capacity is listed under
specific conditions (Example: ARI conditions for air
conditioning compressors is at 130oF (54.4oC)
condensing and 45oF (7.2oC)
evaporator).
A compressor capacity will change as the load changes.
To accurately check compressor capacity one should note
the conditions you are operating at and plot these on a
capacity curve designed for the specific compressor and
refrigerant you are using. In short, the capacity that the compressor is drawing is
specific to the conditions. To obtain capacity data
please check with your nearest
Emerson Wholesaler
or visit Emerson's
Online Product Information (OPI)
database.
Top
Q17. What is considered good oil
pressure?
ANSWER: Good oil pressure
is
20-60 psid, this is the differential between crankcase and
oil pump discharge.
Top
Q18. What are the proper methods to
determine operating superheat, sub-cooling and net oil
pressures?
ANSWER:
-
Superheat at the evaporator should be checked as close
to the end of the coil as possible (preferably near the
expansion valve thermal bulb).
Take the pressure at this location with a pressure tap
or the EPR shrader.
Convert this to saturation temperature and compare it to
the actual temperature obtained near the thermal bulb.
-
Superheat at the compressor should be checked at the
compressor only.
Take the suction pressure at the service valve and
convert it to saturation temperature.
Compare this to the actual temperature obtained
approximately six inches out on the suction line.
-
Subcooling should be checked as close to the inlet of
the evaporator metering device as possible.
Take the pressure of the liquid line near the
metering device inlet and convert this to saturation
temperature.
Compare it to the actual temperature obtained near the
same point the pressure was obtained.
-
Net oil should compare the actual forces that work on
the oil pump.
This includes oil pump outlet pressure and crankcase
pressure (not suction pressure).
The suction pressure on a semi-hermetic refrigerant
cooled compressor may be a couple of pounds pressure
difference from the actual crankcase pressure.
This especially holds true if the compressor is a
two-stage application that has intermediate pressure
working on the crankcase.
Place a gauge manifold on the oil pump discharge
and one on the compressor crankcase, the difference is
net oil pressure.
Top
Q19. Which starting components
should be used with
Emerson Climate Technologies'
new single-phase welded models?
ANSWER:
Only Emerson authorized start components
should be used. We have tested and approved the heavy-duty start components.
Contact your local authorized
Emerson Wholesaler
for proper selection.
Top
Q20. Should a suction line filter
drier be installed before or after an accumulator?
ANSWER:
A drier is designed to be a temporary device to clean a
system after a burnout.
The suction line acts like a chimney during the burn and the
soot carries into the accumulator.
The soot will need to be caught before entering a newly
installed compressor.
For this reason we suggest that the drier be installed
between the compressor and the accumulator.
It should be removed within 48 hours and replaced until
the system is cleaned and acid free.
At this time it may be removed or a filter left in
place. The
filter may be installed up stream of the accumulator to keep
the accumulator from being contaminated.
Top
Q21. Can I use a receiver on a cap
tube system?
ANSWER: The refrigerant charge is critical in
capillary tube systems since normally there is no receiver
to store excess refrigerant. Too much refrigerant will
cause high discharge pressures and motor overloading, and
possible liquid floodback to the compressor during the off
cycle; too little will allow vapor to enter the capillary
tube causing a loss in system capacity.
Top
Q22. Can I directly replace R-12
with R-134a refrigerant?
ANSWER:
Emerson Climate Technologies
does not agree with any so-called direct drop in
replacements.
Refer to
Form
93-04 at Online Product Information
for specific retrofit recommendations.
Briefly, this will include an oil change from mineral
oil to Polyol Ester oil.
The mineral oil must be below 5% total in the system.
The expansion valves may be oversized.
The system must dry and clean.
Top
Q23. Is it acceptable to use R-404A
and AB?
ANSWER:
Emerson Climate Technologies
does not approve the use of Alkyl Benzene oil with R-404A.
R-404A is a HFC and Polyol Ester is the only approved
oil. The Alkyl
Benzene will not be miscible with the HFC.
The HCFC refrigerants have a small amount of chlorine
that is miscible with the AB oil.
Tests have proven that oil return problems result when
AB is used with R-404A.
Top
Q24. Why do refrigeration
manufacturers recommend only 80% to 90% of the original
system charge when retrofitting to some HFCs?
ANSWER:
The
new refrigerants are considered “higher efficient” and they
are trying to sell refrigerants under the requirement of
fewer component change outs.
For example, an expansion valve works to full capacity
if it has full liquid (subcooled liquid) to its inlet.
If the expansion valve is considered oversized for the
new refrigerant then the valve capacity will decrease if the
refrigerant starts to boil off before the inlet of the
valve. The
vapor molecules take up more space than the liquid
molecules, therefore, less refrigerant passes through the
valve with vapor.
Emerson Climate Technologies
recommends valves to be sized accordingly and to charge the
system as basic rules apply:
expansion valves are charged by clearing the sight
glass in the liquid line at high load (subcooling) and the
cap tubes are charged by evaporator superheat at low load
conditions. If
only a percentage of charge is used the compressor could
overheat during an extended high load condition.
Top
Q25. Can I purchase pistons, rods, bearings and
cranks?
ANSWER:
They are not available from Emerson Climate Technologies If these components fail, there’s usually more damage
in the compressor that could cause reduction in capacity,
efficiency and/or additional component failures.
Top
Q26. How can I dispose of my failed compressor?
ANSWER:
-
If a welded compressor is being disposed, the
refrigerant should be recovered and the oil removed.
The compressor should be rendered unusable by
drilling holes in the casing and scrapping the
compressor at a location for metal scraps.
-
If the compressor is a semi-hermetic, a core value may
apply.
Recover the refrigerant from the compressor. After removal from the system, the compressor ports should be
plugged to prevent oil leakage.
It is recommended to use the plugs or shipping pads
of the replacement compressor.
Return to an authorized
Emerson Wholesaler.
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