Carrier COBRA 48/50HJ004-014 Installation And Service page 41

PROBLEM
Compressor and outdoor fan
will not start.
Compressor will not start but
outdoor fan runs.
Compressor cycles (other
than normally satisfying
thermostat).
Suction pressure greater than
100 psig in Cooling mode.
Excessive head pressure.*
Head pressure too low.*
Excessive suction pressure.*
Suction pressure too low.*
LEGEND
TXV — Thermostatic Expansion Valve
*Energy recovery section uses TXVs with a 100 psig maximum operating pressure (MOP) feature to limit suction pressure
in Cooling mode at high temperatures. Always consult charging chart for correct operating pressures.
PROBLEM
Damper does not open; fan(s) off.
Damper will not close.
LEGEND
OCR — Occupied Relay
Table 3 — Heating and Cooling Troubleshooting
CAUSE
Power failure.
Fuse blown or circuit breaker tripped.
Defective thermostat, contactor, transformer, con-
trol relay, or capacitor.
Insufficient line voltage.
Incorrect or faulty wiring.
Light Commercial Thermidistat program in UC1
or UC2 mode.
Defective fan motor.
Faulty wiring or loose connection in compressor
circuit.
Compressor motor burned out, seized, or internal
overload open.
Defective run/start capacitor, overload, start relay,
Time Guard® device.
No DEHUM signal from Light Commercial
Thermidistat.
Time Guard device not timed out.
Refrigerant overcharge or undercharge.
Defective compressor.
Insufficient line voltage.
Blocked outdoor coil or dirty air filter.
Defective run/start capacitor, overload, or start
relay.
Faulty outdoor-fan (cooling) or indoor-fan (heat-
ing) motor or capacitor.
Restriction in refrigerant system.
Defective TXV.
Dirty air filters.
Dirty coils.
Refrigerant overcharged.
Air in system.
Condensing air restricted or air short-cycling.
Low refrigerant charge.
Compressor valves leaking.
Restriction in liquid tube.
High heat load.
Compressor valves leaking.
Refrigerant overcharged.
Dirty air filters or coils.
Low refrigerant charge.
Metering device or low side restricted.
Insufficient indoor airflow.
Table 4 — Supply-Air Damper Troubleshooting
OCR not energized (thermostat in Unoccupied
mode).
OCR defective.
Damper jammed.
Damper motor defective.
Loose wiring.
Damper jammed.
Motor return spring broken.
Call power company.
Replace fuse or reset circuit breaker.
Replace component.
Determine cause and correct.
Check wiring diagram and rewire correctly.
Check Light Commercial Thermidistat program. See Step 5
— Conduct Light Commercial Thermidistat Start-Up and
Checkout on page 33.
Replace fan motor.
Check wiring and repair or replace.
Determine cause. Replace compressor.
Determine cause and replace.
Check for DEHUM signal on Light Commercial Thermidistat
LCD display.
Allow time for Time Guard device to recycle unit.
Recover refrigerant, evacuate system, and recharge to
nameplate.
Replace and determine cause.
Determine cause and correct.
Determine cause and correct.
Determine cause and replace.
Replace.
Locate restriction and remove.
Replace TXV.
Replace filters.
Clean coils.
Recover excess refrigerant.
Recover refrigerant, evacuate system, and recharge.
Determine cause and correct.
Check for leaks; repair and recharge.
Replace compressor.
Remove restriction.
Check for source and eliminate.
Replace compressor.
Recover excess refrigerant.
Replace filter, clean coils.
Check for leaks; repair and recharge.
Remove source of restriction.
Increase air quantity. Check filter and replace if necessary.
CAUSE
Check Light Commercial Thermidistat program
settings (see Step 5 — Light Commercial Thermi-
distat Start-Up and Checkout section, page 33).
Replace OCR.
Free damper.
Replace damper motor.
Check wiring and correct.
Free damper.
Replace motor.
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REMEDY
REMEDY