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1 2010 Emerson Climate Technologies
Printed in the U.S.A.
AE4-1307 R1
Application Engineering
B U L L E T I N
New hermetic compressors and condensing unitshave been developed
utilizing R-404A/507 refrigerantssuitable for Low Temperature
applications. It must benoted, however, that under low evaporating
temperatureconditions, the operating envelope for these models
willbe restricted especially in comparison to
semi-hermeticcompressors typically used in similar applications.The
operating envelope and restrictions are shown in
Figure 1.
For a given saturated suction temperature, themaximum condensing
temperature, the maximumreturn gas temperature, and the maximum
dischargeline temperature as outlined in Figure 1must not
beexceeded! Operation beyond these limits will causehigh
compression ratios and/or excessive internalcompressor temperatures
resulting in overheatingconnecting rod wear and premature
compressor failure.
If the system design is such that operation within
theseguidelines cannot be guaranteed, then the followingadditional
controls must be added:
1. Discharge Line Thermostat: Located 6 inchesform the
compressor and Set to cut-out thecompressor at 225F maximum
2. Low Pressure Control: Set to cut-out at 7 psigminimum.
Superheat Requirements
In order to ensure that liquid refrigerant does not returnto
compressor during the running cycle, attentionmust be given to
maintaining proper superheat atthe compressor suction inlet.
Emerson ClimateTechnologies recommends a minimum of 20Fsuperheat,
measured on the suction line 6 inches fromthe suction inlet, to
prevent refrigerant floodback.
Another method to determine if liquid is coming back tothe
compressor is to accurately measure the differencein temperature
between the compressor lower shellopposite the suction inlet and
the suction line. If thisdelta can be kept at a minimum of 50F, no
liquid willbe present in the crankcase.
Suction Accumulator Requirements
Through our development testing we have found thecombination of
HFC refrigerants and polyol ester oildevelop very high cylinder
pressures during floodedstart conditions. As a result of this
testing, we have setthe maximum charge limit to be 6 lbs.
Any system that exceeds the charge limit will require
a suction accumulator and/or pumpdown cycle. Thepurpose of these
precautions is to prevent damage to thecompressor due to continuous
floodback and/orfloodedstart conditions. An accumulator is an
effective measureagainst floodback and provides some protection
againstflooded starts; however, the pumpdown cycle is the
mostpositive means of preventing flooded start conditions.
Crankcase Heater Requirements
Crankcase heaters are recommended on all outdoorapplications or
indoor applications if expected tooperate in ambients below 40F,
orany system withan accumulator.
LubricantsHFC refrigerants such as R-404A and R-507
requirepolyol ester lubricants to provide proper miscibility
andlubricity. Emerson has approved only the followinglubricants at
this time:
Copeland Ultra 22CC Mobile EAL Arctic 22CC ICI Emkarate RL32CF
Thermal Zone 22CC
Should a system require the addition of lubricant forany reason,
only the lubricants specified above shouldbe used.
Practical Considerations
The application restrictions imposed on these modelswill require
careful system design. Some considerationsfor the designer are:
1. Units operating at low evaporator temperatureswill be
susceptible to overheating with dirtycondensers and/or restricted
air flow. Large
Application Guidelines forCF Refrigeration Compressors and
Condensing Units
AE4-1307 R1 February 2000Reformatted November 2010
Application Engineering
B U L L E T I N
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2 2010 Emerson Climate Technologies
Printed in the U.S.A.
AE4-1307 R1
Application Engineering
B U L L E T I N
condensers (with low TDs) should be designedinto systems using
these compressors andproper condenser coil maintenance
isrequiredand regular cleaning practices should befollowed.
2. Minimum suction line pressure drops willbe important to
maintain Saturated SuctionTemperature limits at the compressor.
3. Traditional superheat settings at the ThermalExpansion Valves
may be too high to maintainthe return gas temperature limits
specified.
4. Suction lines should be well insulated.
5. Suction line to liquid heat exchangers maynot be desirable if
return gas temperaturesspecified are to be maintained.
Figure 1
60
70
80
90
100
110
120
130
140
150
-40 -30 -20 -10 0 10 20 30 40
EVAPORATING TEMPERATURE (oF)
CONDENSING
TEMPERATURE
(oF)
CF Envelope
Evap Temp Max Return Max Cond Max Disch
(SST)*(F) Gas (F) Temp (F) Line (F)
10 40 140 225
5 40 140 225
0 40 140 225
-5 40 140 225
-10 40 140 225
-15 40 140 225
-20 40 130 225-25 40 125 225
-30 40 120 225
