Carrier 30GA - Manual (Page 11)

With no refrigerant returning to the compressor,
low side pumpout takes place and the compressor
shuts down on low-pressure control. The compres­
sor will not restart until the WTC again calls for
cooling.
HOT GAS BYPASS
On the last step of capacity control (only WTC
switch no. 1 made), the Hot Gas Bypass valve is
energized. This allows the unit to operate at a
lower load condition than is provided in the normal
function of the WTC, with less on-off cycling of
the compressor.
TROUBLESHOOTING
SYMPTOMS PROBABLE CAUSE REMEDY SYMPTOMS PROBABLE CAUSE
Compressor does Power line open Reset circuit breaker Unit operates Low refrigerant charge
not run Control circuit Check control circuit
long or Control contacts fused
breaker tripped for ground or short;
continuously
Air in system
repair and reset
Partially plugged or
breaker plugged expansion
Safety thermostat Reset thermostat valve or strainer
tripped System Noises Piping vibration
Tripped starter Check the controls
overloads Find cause of trip
and reset overloads
Contactor stuck open Replace contactor
Compressor noisy
Loose terminal
connection
Check connections
Improperly wired Check wiring and
controls rewire
Low line voltage Check line voltage —
determine location Compressor Leak in system
of vol Lage drop and loses oil
Crankcase heater
remedy deficiency
not energized dur-
Compressor motor Check motor wind- ing shutdown
defective ing for open or short
Replace compressor,
Frosted or Expansion valve
if necessary
sweating sue- admitting excess
Seized compressor Replace compressor tion line refrigerant
Compressor Low-pressure control Raise differential Hot liquid line Shortage of refrigerant
stops on erratic in action setting due to leak
low-pressu re Check capillary for
Expansion valve
control pinches
opens too wide
Replace control
. . . .
Frosted liquid Restricted
Compressor suction Open valve line filter-drier
shutoff valve
Compressor will Burned out coil
partially closed
Low refrigerant charge Add refrigerant
not unload Leaky bypass piston
Liquid line Check liquid line
Miswired solenoid
solenoid valve(s) solenoid valve(s) Weak bypass piston
fails to open and coils for Spring
proper operation Compressor will Damaged bypass
Replace if necessary not load piston
Compressor High-pressure control Check capillary tube Miswired solenoid
cyles on high- erratic in action for pinches
Plugged bypass
pressure control Set control as
port strainer
required
(high side)
Compressor discharge Open valve, or re- High Suction Stuck check valve
valve partially closed place if defective in valve plate
Air in system Purge
Condenser fan(s) Check motor and Chattering Stuck check valve
not operating wiring Repair or unloader in valve plate
replace if defective ____________
REMEDY
Add refrigerant
Replace control
Purge
Clean or replace
Support piping as
required
Check for loose pipe
connectors
Check vaive plates
for valve noise
Replace compressor
(worn bearings)
Check for loose
compressor hold­
down bolts
Repair leak
Check wiring and
relay Check
heater — replace
if defective
Adjust expansion
valve
Repair leak and
recharge
Adjust expansion
valve
Remove restriction
or replace filter-drier
Replace coil
Replace
Wire correctly
Replace
Replace
Wire correctly
Clean
Examine check valve
components Clean or
replace as necessary
Examine check valve
components Clean or
replace as necessary
11