Cambridge Air Solutions
32
SA-Series Technical Manual
Problem
Possible Cause
Corrective Action
VI. HIGH LIMIT TRIPPED
1. High Limit
a) High limit will not reset
a) Replace high limit
2. Unit Overfiring
a) Manifold pressure too high
a) Adjust combination valve to obtain
temperature rise specified on nameplate
3. Inlet Damper (optional)
a) Damper blades partially closed
b) Defective damper motor
a) Adjust damper
b) Replace damper assembly
4. Low Airflow
a) Blower running backwards (SA350)
b) Belts slipping (SA350)
c) Blocked intake or discharge
a) Reverse motor direction (SA350)
b) Tighten and/or replace belts (SA350)
c) Find and remove obstruction
5. Temperature Control System
a) Temperature control system does not
modulate
a) See problem VIII
VII. BLOWER RUNS;
UNIT HEATS;
WILL NOT CYCLE
OFF
1. Operating Thermostat
a) Thermostat located improperly
b) Thermostat differential setting too wide
c) Defective thermostat
a1) Thermostat in cold draft-relocate
a2) Thermostat not satisfied-turn down
b) Reduce differential setting
c) Replace thermostat
2. Burner Service Switch
a) Switch in LOCAL position
a) Place switch in REMOTE position
3. Auxiliary Control
a) Auxiliary contacts closed
a) Check auxiliary circuit wiring and
contacts
4. Misunderstood Control System
Operation
a) Control system doesn’t function as
expected
a) Review control system operational
characteristics
VIII. MODULATING
VALVE DOES NOT
MODULATE;
CONTINUOUS
HIGH FIRE
(Continued on
next page)
1. Amplifier
a) Wire not connected to amplifier terminal
3, 4, or 5
b) Defective amplifier
a) Reinstall wire
b) Replace amplifier
2. Discharge Temperature Sensor
a) Discharge Air Temperature Sampling
Tube clogged
b) Open in sensor circuit
c) Sensor cross-wired to amplifier
d) Temperature Control System out of
calibration
a) Clean Discharge Air Temperature
Sampling Tube
b) Replace the sensor if resistance measured
at terminals 1 and 3 or 2 and 3 exceeds
6,000Ω
c) Correct wiring terminations
d) Perform appropriate calibration procedure
(page 17)
TROUBLESHOOTING INSTRUCTIONS
TROUBLESHOOTING GUIDE
