17
SYMPTOM
High head - low suction
a.
Restriction in liquid line or
TXV not functioning
a. Remove or replace with proper size TXV.
High head - high or normal suction
a. In Cooling: Dirty condenser coil
a. Clean coil
In Heating: Dirty filter, Dirty indoor coil
b. Overcharged
b. Correct System charge
c. In Cooling: Condenser fan not running
c. In Heating: Indoor blower not running
c.
Repair or Replace
a. Incorrect TXV.
a. Replace with correct TXV
b. Defective compressor valves
b.
Replace compressor
c. TXV not functioning properly
c. Check for debris in TXV or deformed TXV.
Remove debris or replace TXV.
d. Incorrect TXV setting
d. Check Super Heat
a. Power off or loose electrical connection
a. Check for unit voltage at contactor in unit
b. Thermostat out of calibration set too high b.
Reset
c. Defective contactor
c. Check for 24 volts at contactor coil replace if
contacts are open
d. Blown fuses or tripped breaker
d. Replace fuse or reset breaker
e. Transformer defective
e.
Check wiring - replace transformer
f. High or low pressure control open
(Optional)
f. Check high pressure control or check unit
charge
High pressure control opens at 610 psig
Low pressure control opens at 22 psig
g. Compressor overload contacts open
g.
Replace compressor
NOTE: Wait at least 2 hours for overload to reset
Condenser fan runs,
compressor doesn't
a. Loose connection
a. Check for unit voltage at compressor check &
tighten all connections
b. Compressor stuck, grounded or open
winding
open internal overload
b. Wait at least 2 hours for overload to reset If still
open, replace the compressor.
c. Low voltage connection
c. At compressor terminals, voltage must be within
10 % of nameplate volts when unit is operating
d. Capacitor weak, open, or shorted
d. Check capacitor. If defective, replace.
Low suction - cool compressor
a. In Cooling: Low indoor airflow
a.
Iced evaporator coil
In Heating: Dirty outdoor coil, defective
defrost thermostat, defective defrost
control board, outdoor fan not running, low
refrigerant charge.
b. Low airflow
b. Check - should be approximately 400 CFM per
ton, dirty air filters, all duct outlets open
c. Low refrigerant charge
c.
Properly charge unit
d. Operating unit in cooling mode below 65°F
outdoor temperature
d. Install or check low ambient control, should be
open below 65°F outdoor temperature
a. Defective overload protector
a. Replace - check for correct voltage
b. Unit cycling on low pressure control
b. Check refrigerant charge and / or airflow
c. High pressure switch cuts out
c. Check airflow (indoor & outdoor),
check expansion device
a.
a. Increase speed of blower or reduce restriction
replace air filters
a. Excessive load
a.
Recheck load calculation
b. Defective compressor
b.
Replace
c. Reversing valve not seating properly.
c.
Replace
a.
Improperly sized unit
a.
Recalculate load
b. Improper airflow
b. Check - should be approximately 400 CFM per ton
c. Incorrect refrigerant charge.
c. Charge per procedure attached to unit service
panel
d. Incorrect voltage
d. At compressor terminals, voltage must be within
10% of nameplate volts when unit is operating
Increase speed of blower or reduce restriction -
replace air filters
Insufficient cooling
High suction pressure
REMEDY
POSSIBLE CAUSE
Compressor short cycles
Registers sweat
Low airflow
Low head - high suction
Unit will not run
APPENDIX
TROUBLESHOOTING
