Specifications

25
6.2. Mechanical System Troubleshooting
Issue Possible Cause Remedy
Supply blower will not start
Firestat contact closure Check firestat switch
Loss of main power
Check for tripped circuit
breaker or blown fuses
Manually shut down on
controller
Restart
Faulty control wiring
Check for loose or incorrect
wires on system and controller
Faulty wiring
Check for loose or faulty wiring
on system and controller
Motor windings have shorted Replace motor
Blower overload has tripped reset overload
Compressor will not start
Manually shut down on
controller
Restart
Faulty control wiring
Check for loose or incorrect
wires on system and controller
No demands to run
Adjust setpoints to what is
indicated on the unit
Nameplate
Loss of main power
Check for tripped circuit
breaker or blown fuses
Blower not operating
Refer to supply blower
problem section
Faulty wiring
Check for loose or faulty wiring
on system and controller
Compressor thermal protector
is open
Allow one hour for compressor
to cool off.
Compressor delay-timer Wait 3 minutes for timer
Compressor overload has
tripped
Correct cause and reset
overload
Compressor draws locked
rotor amps
Replace compressor (or check
fuses on three-phase units)
Motor windings have shorted Replace compressor
Compressor starts but does
not pump
Replace compressor
Low Suction pressure
Normal: 60 – 75 PSIG
Excessive bubbles in sight
glass (more than 10% of
volume)
Lack of refrigerant. Check
receiver sight glasses –level
indicators. Is the bottom ball
floating?
Blocked filter drier.
Return air is below 70°F
Is cold outdoor air mixing
upstream of the coil?
Too much cold outdoor air
being introduced to the space.
Duct heater not able to
accommodate actual load.
Review space heating
requirement.