15
© 2015 Emerson Climate Technologies, Inc.
AE4-1365 R4
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. Before replacing or returning a compressor, be
certain that the compressor is actually defective.
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.
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 55 psig (3.8 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 55 psig (3.8 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.
