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8. Repeat steps 1 through 8 for the number 2 refrigeration
circuit.
9. After shutting the system off, check the compressor oil
appearance. Discoloration of the oil indicates that an
abnormal condition has occurred. If the oil is dark and
smells burnt, it has overheated because: the
compressor is operating at extremely high condensing
temperatures; high superheat; a compressor
mechanical failure; or, occurrence of a motor burnout.
If the oil is black and contains metal flakes, a
mechanical failure has occurred. This symptom is often
accompanied by a high compressor amperage draw.
If a motor burnout is suspected, use an acid test kit to
check the condition of the oil. Test results will indicate
an acid level exceeding 0.05 mg KOH/g if a burnout
occurred.
The scroll compressor uses Trane OIL00079 (one quart
container) or OIL00080 (one gallon container) without
substitution. The appropriate oil charge for CSHN184/
CSHL169, CSHN250/CSHL227 and CSHL285 scroll
compressors is 14.2 pints. For CSHL346 scroll
compressor, use 15.2 pints.
Compressor Crankcase Heaters
Each scroll compressor is equipped with a 160-watt
crankcase heater.
Table 55. Crankcase heater sizes
Compressor Name
ZPS*
ZP*
CSHD*
VZH088*, VZH117*
VZH170*
CSHN/CSHL*
Compressor Operational Sounds
Because of the scroll compressor design, it emits a higher
frequency tone (sound) than a reciprocating compressor. It
is designed to accommodate liquids, both oil and
refrigerant, without causing compressor damage. The
following sections describe some of the operational sounds
that differentiate it from those typically associated with a
reciprocating compressor. These sounds do not affect the
operation or reliability of the compressor.
At Shutdown
When a Scroll compressor shuts down, the gas within the
scroll expands and causes momentary reverse rotation
until the discharge check valve closes. This results in a
"flutter" type sound.
RT-SVX073A-EN
Crankcase Heater Watts
70
90
160
At Low Ambient Start-Up
When the compressor starts up under low ambient
conditions, the initial flow rate of the compressor is low due
to the low condensing pressure. This causes a low
differential across the expansion valve that limits its
capacity. Under these conditions, it is not unusual to hear
the compressor rattle until the suction pressure climbs and
the flow rate increases.
Variable Speed Compressors
At all operating speeds, eFlex™ permanent magnet
variable speed compressors sound different than fixed
speed scrolls. At low speed, variable speed compressors
can sputter. At high speed, variable speed compressor
buzz. These are normal operating sounds. To ensure a
quiet installation, eFlex variable speed compressors are
installed in a sound enclosure. Make sure and keep the
sound enclosure installed at all times other than servicing.
Important: Variable speed scroll compressors sound
different than single speed scroll compressors.
Sound changes with speed and condition.
Electronic Compressor
Protection Module (CPM)
The CSHN/CHSL*** compressors come equipped with a
compressor protection device (CPM) capable of detecting
phase reversal, phase loss, and motor overheating. When
a fault is identified, the output relay will open. Depending
on the fault, the CPM may either auto-reset or it may lock-
out. The CPM can be manually reset by cycling control
power.
Note: If the compressor has tripped due to an overheated
windings condition, the motor winding temperature
sensor resistance (PTC) will be 4500 ohms or
greater; the resistance must be less than 2750 ohms
before the 5 minute reset timer becomes enabled.
Figure 104. Compressor locations and staging
sequence (fixed speed compressors)
Unit Startup
Compressor 2B
Compressor 2A
Compressor 1B
Compressor 1A
155
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