6
© 2015 Emerson Climate Technologies, Inc. All rights reserved.
AE4-1395 R5
valves, therefore high pressure controls are required
in some applications. The recommended maximum cut
out setting is 425 psig (30 bar) for R-407C & R-22 and
650 psig (45 bar) for R-410A. The high pressure control
should have a manual reset feature for the highest
level of system protection. This pressure control must
act independently of the digital compressor controller.
Low Pressure Control
Air-conditioning units can be protected against high
discharge temperatures through a low pressure control in
the suction line. Testing has shown that a cut out setting
of not lower than 55 psig (3.8 bar) for R-410A and 25
psig (1.7 bar) for R-407C & R-22 will adequately protect
the compressor against overheating from loss of charge,
blower failure in a TXV system, etc. A higher level of
protection is achieved if the low pressure control is set to
cut out at 95 psig (6.7 bar) for R-410A and 55 psig (3.8
bar) for R-407C & R-22 to prevent evaporator coil icing.
The cut in setting can be as high as 180 psig (12.5 bar)
for R-410A and 105 psig (7.2 bar) for R-407C & R-22 to
prevent rapid recycling in case of refrigerant loss.
For heat pumps, a cut out setting no lower than 20 psig
(1.4 bar) is recommended for R-410A and 10 psig (0.7
bar) for R-407C & R-22.
Scroll Temperature Protection
Most digital scrolls do not have internal discharge
gas temperature protection. In order for the Emerson
controllers to operate properly an NTC sensor must be
attached to the compressor discharge line as close as
possible to the compressor discharge tting. For best
response the sensor should be insulated. See Table 6
of AE8-1328 for thermistor temperature vs. resistance
values. Refer to Table 4 for part numbers of discharge
line thermistors. Figure 5 illustrates the two different
types of discharge thermistors.
The ZRD61 through ZRD81KC compressors have a
discharge thermistor that is inside of a well in the top
cap of the compressor. If this thermistor ever needs to
be replaced, it should be replaced with either 985-0199-
00 or 085-0204-00 as listed in Table 4.
Crankcase Heaters
A crankcase heater is required if the system charge
exceeds the system charge limits listed in Table 2.
For more information regarding regarding heater part
numbers and installation location please refer to the
equivalent non-digital scroll Application Engineering
bulletin listed on Page 4.
Oil Type and Oil Removal
Mineral oil is used in the ZRD*KC compressors for
R-22 applications. Polyolester (POE) oil is used in
the ZRD*KCE and ZPD*KCE compressors for R-22
& R-407C and R-410A applications respectively. See
the compressor nameplate for the original oil charge. A
completerechargeshouldbeapproximatelyfouruid
ounces (118 ml) less than the nameplate.
It is an approved practice to use ZRD*KCE compressors
with POE to replace ZRD*KC compressors with mineral
oil in R-22 service applications. R-22 has been approved
for use with both mineral and POE and some mixing of
these oil in the system is acceptable.
If additional oil is needed in the field for POE
applications, Copeland
™
Ultra 32-3MAF, Lubrizol
Emkarate RL32-3MAF, Parker Emkarate RL32-3MAF/
Virginia LE32-3MAF, or Nu Calgon 4314-66 (Emkarate
RL32-3MAF) should be used. Copeland Ultra 22 CC,
Hatcol EAL 22CC, and Mobil EAL Arctic 22 CC are
acceptable alternatives.
If additional oil is needed in the eld for mineral oil
applications, Sonneborn Suniso 3GS or Chevron
Texaco Capella WF32 should be used.
POE must be handled carefully and the proper
protective equipment (gloves, eye protection, etc.)
must be used when handling POE lubricant. POE
must not come into contact with any surface or
material that might be harmed by POE, including
without limitation, certain polymers (e.g. PVC/CPVC
and polycarbonate).
Power Factor
During the loaded state the digital scroll compressor
operates at full capacity and the power factor is the
same as a standard scroll. However, when the scrolls are
unloaded, the power factor is much lower. If power factor
is an important consideration, the correcting capacitors
should be calculated using the full capacity data to avoid
problems associated with over correction. See AE9-1249
for more information on power factor correction.
Tandem Applications
Tandem compressors follow the same application
guidelines as single compressors outlined in this bulletin.
The refrigerant charge limit for tandem compressors is
To Next Page
Loading...
Need help?
General
