Application Engineering
B U L L E T I N
AE4-1374 R1
does not rise to normal levels, reverse any two of
the compressor power leads and reapply power
to make sure the compressor was not wired to
run in reverse. If pressures still do no move to
normal values, either the reversing valve (if so
equipped) or the compressor is faulty. Reconnect
the compressor leads as originally configured
and use normal diagnostic procedures to check
operation of the reversing valve.
7. To test if the compressor is pumping properly,
the compressor current draw must be compared
to published compressor performance curves
using the operating pressures and voltage of the
system. If the measured average current deviates
more than +/-20% from published values, a
faulty compressor may be indicated. A current
imbalance exceeding 20% of the average on the
three phases of a three-phase compressor should
be investigated further. A more comprehensive
trouble-shooting sequence for compressors and
systems can be found in Section H of the Emerson
Climate Technologies Electrical Handbook,
Form No. 6400.
8. Note that the ZR16-32K5 three-phase motors use
a modified "Scott-T" connection and don't have
equal resistances on all three windings. Two
windings will have equal resistances and the
third winding will be up to 30% different from the
other two. Carefully compare measured motor
resistance values to the two different published
resistance values for a given compressor model
before replacing the compressor as being
defective. The larger ZR38 to 54K5 compressors
have conventional three-phase motors with equal
resistances in each winding.
9. Before replacing or returning a compressor, be
certain that the compressor is actually inoperative.
As a minimum, recheck compressors returned
from the field in the shop or depot by testing for a
grounded, open or shorted winding and the ability
to start. The orange tag in the service compressor
box should be filled out and attached to the failed
compressor to be returned. The information on this
tag is captured in our warranty data base.
© 2013 Emerson Climate Technologies, Inc.
Printed in the U.S.A.
Compressor Replacement After a Motor Burn
In the case of a motor burn, the majority of contaminated
oil will be removed with the compressor. The rest of the
oil is cleaned with the use of suction and liquid line filter
driers. A 100% activated alumina suction filter drier is
recommended but must be removed after 72 hours. See
AE24-1105 for clean up procedures and AE11-1297 for
liquid line filter-drier recommendations. NOTICE It is
highly recommended that the suction accumulator
be replaced if the system contains one. This is
because the accumulator oil return orifice or screen may
be plugged with debris or may become plugged shortly
after a compressor failure. This will result in starvation of
oil to the replacement compressor and a second failure.
The system contactor should be inspected for pitted/
burnt contacts and replaced if necessary. It is highly
recommended that the run capacitor be replaced when
a single phase compressor is replaced.
Start-Up of a New or Replacement Compressor
It is good service practice, when charging a system
with a scroll compressor, to charge liquid refrigerant
into the high side only. It is not good practice to dump
liquid refrigerant from a refrigerant cylinder into the
crankcase of a stationary compressor. If additional
charge is required, charge liquid into the low side of
the system with the compressor operating. CAUTION!
Do not start the compressor while the system is in
a deep vacuum. Internal arcing may occur when any
type of compressor is started in a vacuum. NOTICE Do
not operate the compressor without enough system
charge to maintain at least 20 psig (1.4 bar) suction
pressure. Do not operate with a restricted suction
or liquid line. Do not operate with the low pressure
cut-out disabled. Allowing suction pressure to drop
below 20 psig (1.4 bar) for more than a few seconds
may overheat the scrolls and cause early drive bearing
damage. Never install a system in the field and leave
it unattended with no charge, a holding charge, or with
the service valves closed without securely locking out
the system. This will prevent unauthorized personnel
from accidentally ruining the compressor by operating
with no refrigerant flow.
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