Application Engineering
B U L L E T I N
AE4-1374 R1
Introduction
The ZR*K5 Copeland Scroll
™
compressors are
designed for residential and light commercial R-407C
air-conditioning and heat pump applications and R-22
service applications. A typical model number is ZR28K5-
PFV. This bulletin describes the operating characteristics,
design features and application requirements for these
models. For additional information, please refer to Online
Product Information accessible from our website at
www.emersonclimate.com. Operating principles of the
Copeland Scroll compressor are described in Figure 9 at
the end of this bulletin. The scroll compressors outlined
in this bulletin range in size from 14,650 Btu/hr to 53,500
Btu/hr (4.3 - 15.7 kW) and include common 50 and 60
Hertz, single and three phase voltages.
The models include a number of features outlined in
the matrix below.
Nomenclature
The model numbers of the Copeland Scroll compressors
include the approximate nominal 60 Hz capacity at
standard operating conditions. An example would
be the ZR28K5-TFD, which has 28,400 Btu/hr (8.3
kW) cooling capacity at the ARI high temperature air
conditioning rating point when operated at 60 Hz. Note
that the same compressor will have approximately 5/6
of this capacity or 23,300 Btu/hr (6.8 kW) when operated
at 50 Hz. Please refer to Online Product Information at
www.emersonclimate.com for details.
Application Considerations
The following application guidelines should be
considered in the design of a system using ZR*K5
scroll compressors. Some of this information is
recommended, whereas other guidelines must be
followed. The Application Engineering department will
always welcome suggestions that will help improve
these types of documents.
Internal Pressure Relief (IPR) Valve
The internal pressure relief valve is located between
the high and low side of the compressor. It is designed
to open when the discharge-to-suction pressure
differential exceeds 375 to 450 psid (26-31 bar). When
the valve opens, hot discharge gas is routed back into
the area of the motor protector to cause a trip. During
fan failure testing, system behavior and operating
pressures will depend on the type of refrigerant metering
device. Fixed orifice devices may flood the compressor
with refrigerant, and thermostatic expansion devices
will attempt to control superheat and result in higher
compressor top cap temperatures. Fan failure testing
or loss of air flow in both cooling and heating should
be evaluated by the system designer to assure that the
compressor and system are protected from abnormally
high pressures.
Discharge Temperature Protection
CAUTION
Compressor top cap temperatures can be very
hot. Care must be taken to ensure that wiring or
other materials which could be damaged by these
temperatures do not come into contact with these
potentially hot areas.
The Therm-O-Disc
™ or TOD is a temperature-sensitive
snap disc device located on the muffler plate. It is
designed to open and route excessively hot discharge
gas back to the motor protector when the internal
discharge gas exceeds 290°F (144°C). During a situation
such as loss of charge, the compressor will be protected
for some time while it trips the protector. However, as
refrigerant leaks out, the mass flow and the amperage
draw are reduced and the scrolls will start to overheat. A
low pressure control is recommended for loss of charge
protection for the highest level of system protection.
The low pressure cut-out can provide protection against
indoor blower failure in cooling, outdoor fan failure in
heating, closed liquid or suction line service valves,
or a blocked liquid line screen, filter, orifice, or TXV.
All of these can starve the compressor of refrigerant
and result in compressor failure. The low pressure
cut-out should have a manual reset feature for the
highest level of system protection. If a compressor is
allowed to cycle after a fault is detected, there is a high
probability that the compressor will be damaged and
the system contaminated with debris from the failed
compressor and decomposed oil. If current monitoring
of the compressor is available, the system controller
can take advantage of the compressor TOD and internal
Model
Motor
Application
Frame Size*
AC
HP
Quiet
IPR
TOD
Shutdown
Discharge
Motor
Electrical
Check Valve Protector
Connections
ZR16-32K5
53
X
X
X
X
X
X
X
Molded Plug
ZR38-54K5
63
X
X
X
X
X
X
X
Molded Plug
* Approximate Shell Diameter (e.g. 53 = 5.5" and 63 = 6.5")
© 2013 Emerson Climate Technologies, Inc.
4
Printed in the U.S.A.
