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© 2015 Emerson Climate Technologies, Inc.
AE4-1331 R7
no pressure differential as compared to normal values.
A compressor running in reverse will sometimes make
an abnormal sound.
There is no negative impact on durability caused by
operating three phase Copeland Scroll compressors in
the reversed direction for a short period of time (under
one hour). After several minutes of reverse operation,
the compressor’s internal overload protector will trip
shutting off the compressor. If allowed to repeatedly
restart and run in reverse without correcting the
situation, the compressor bearings will be permanently
damaged because of oil loss to the system. All three-
phase scroll compressors are wired identically
internally. As a result, once the correct phasing is
determined for a specific system or installation,
connecting properly phased power leads to the
identified compressor electrical (Fusite
™
) terminals will
maintain the proper rotational direction (see
Figure
4
). It should be noted that all three phase scrolls will
continue to run in reverse until the internal overload
protector opens or the phasing is corrected.
Brief Power Interruptions
Brief power interruptions (less than ½ second) may
result in powered reverse rotation of single-phase
Copeland Scroll compressors. This occurs because
high-pressure discharge gas expands backward
through the scrolls during interruption, causing the scroll
to orbit in the reverse direction. When power is reapplied
while reverse rotation is occurring, the compressor
may continue to run in the reverse direction for some
time before the compressor’s internal overload trips.
This will not cause any damage to the compressor, and
when the internal overload resets, the compressor will
start and run normally.
To avoid disruption of operation, an electronic control
that can sense brief power interruptions may be used
to lock out the compressor for a short time. This control
could be incorporated in other system controls (such
as defrost control board or the system thermostat), or
can be a stand-alone control. Functional specifications
for this control as well as a suggested wiring diagram
are shown in
Figure 3
. No time delay is necessary for
three phase models since the motor starting torque is
high enough to overcome reverse rotation.
A start kit (specified start capacitor and relay) is another
effective means of mitigating a powered reverse
condition that is caused by a brief power interruption.
Manifolding Tandem Compressors
All of the ZPK5 compressors are available for
manifolding with another ZPK5 compressor of equal
capacity. These compressors are designated with a
-4XX bill of material number at the end of the model
number (e.g. ZP25K5E-PFV-498). See
Figure 10
for a
picture of an assembled tandem showing the hardware
and parts required for assembly. Drawings of tandem
tubing assemblies are available from Emerson Climate
Technologies by contacting your Applications Engineer.
Tandem Applications
Tandem compressors following the same application
guidelines as single compressors outlined in this
bulletin. The refrigerant charge limit for tandem
compressors is shown in
Table 5
. A three-phase unit
with a charge over this limit must have crankcase
heaters applied to both compressors.
The compressors in a tandem set can be started/
stopped in any desired sequence. To help reduce the
probability of light dimming, starting the compressors
individually is recommended.
Maximum Tilt Angle
OEms and end-users often ask about the maximum
allowable tilt angle of the compressor. Some
applications, such as transportation air-conditioning or
mobile radar applications, may require the compressor
to operate at some angle from vertical. Or, service
personnel may be required to maneuver a unit through
a stairwell or other cramped area that might require
tilting the unit. The maximum allowable tilt angles from
horizontal are summarized below:
Max Tilt Angle With Compressor Running = 15°
Max Tilt Angle With Compressor Not Running = 60°
APPLICATION TESTS
Application Test Summary
There are a minimal number of tests the system
designer will want to run to ensure the system operates
as designed. These tests should be performed during
system development and are dependent on the system
type and amount of refrigerant charge. These application
tests are to help identify gross errors in system design that
may produce conditions that could lead to compressor
failure. The Continuous Floodback Test and Field
Application Test, both outlined below, are two tests to
run to help verify the design. When to run these tests
can be summarized as follows:
Continuous Floodback:
Required on all heatpumps.
Field Application Test:
Required for any unit where both the design system
charge is higher than the compressor refrigerant
