Operating instructions

TM 11574A-OI
C-3/(C-4 Blank)
COMPRESSOR DOES NOT RUN
• Main power line open – replace fuse or reset
circuit breaker
• Safety thermostat tripped – reset thermostat
• Control stuck open – replace control
• Loose terminal connections – check connections
• Improperly wired controls - Check wiring and
rewire
• Low line voltage – Check line voltage. Determine
location of voltage drop
• Compressor motor defective – Check motor
winding for open or short. Replace compressor if
necessary
• Seized compressor – Replace compressor
COMPRESSOR CYCLES ON LOW PRESSURE
CONTROL
• Low pressure control erratic in action – Raise
differential setting, check capillary for pinches,
replace control
• Suction shutoff valve partially closed – Open
valve
• Low refrigerant charge – Add refrigerant
• Plugged suction strainer – Clean strainer
• Defective TXV – Replace TXV
COMPRESSOR
CYCLES ON HIGH PRESSURE
CONTROL
• High pressure control erratic in action – check
capillary tube for pinches, Set control as required
• Discharge valve partially closed – Adjust valve
• Air in system – recover
• Condenser scaled (or airflow restricted) – Clean
condenser
• Refrigerant Overcharge – Recover
INSUFFICIENT CAPACITY
• Low refrigerant charge – Add refrigerant
• Control set too high – reset control
• Expansion valve plugged – clean or replace
• Inefficient compressor – check valves and pistons
• Expansion valve setting too high – lower setting
• Iced or dirty evaporator – defrost or clean
UNIT OPERATES LONG OR CONTINUOUSLY
• Low refrigerant charge – Add refrigerant
• Control contacts fused – replace controls
• Air in system – recover
• Partially plugged or plugged expansion valve or
strainer – clean or replace
• Defective insulation – replace or repair
• Service load – Keep doors and windows closed
• Inefficient compressor – check valves
• Condenser scaled – clean condenser
• Restricted evaporator air –
defrost coil, clean filters
and ductwork
SYSTEM NOISES
• Piping vibration – Support piping as required,
check for plugged liquid line strainer
• Expansion valve hissing – add refrigerant, check
for plugged liquid line strainer
• Compressor noisy – check valve plates for valve
noise, replace compressor (worn bearings), check
for loose compressor hold down bolts
• Inefficient compressor oil – add oil
COMPRESSOR LOSES OIL
• Leak in system – repair leak
• Plugged or stuck compressor oil return check valve
– repair or replace
• Oil trapping in line – check piping for oil traps
FROSTED SUCTION LINE
• Expansion valve admitting excess refrigerant –
adjust expansion valve
HOT LIQUID LINE
• Shortage of refrigerant – repair leaks and recharge
FROSTED LIQUID LINE
• Receiver shutoff valve partially closed or restricted
– Open valve or remove restriction
• Restricted strainer dryer – replace
FROSTED EXPANSION VALVE
• Ice plugging TXV orifice – apply hot wet cloth to
TXV
• Moisture indicated by increase in suction pressure –
install drier
• Plugged TXV strainer – clean strainer or replace
TXV