MUA-SVX01A-EN • Direct-Fired Make-up Air
79
Trouble Shooting
Motor may be burned or
incorrectly wired.
a. Turn power off and check
motor and wiring.
Motor overheating.
a. Check burner firing rate.
2. If there is no voltage at
flame safeguard relay input
terminal.
HEAT-OFF-ON switch in OFF
position.
a. Switch to ON position.
Auxiliary switch on starter
not closed.
a. Check auxiliary circuit wiring
and contact.
Airflow switches open.
a. Adjust the airflow and
external static pressure to
match the rating plate.
Outside air temperature
higher than ON-OFF inlet
ductstat setting (if
applicable).
a. Check stat for proper setting.
High temperature limit
thermostat open.
a. Reset control and correct
problem before restarting.
HIGH-LOW gas pressure
switch open (if applicable).
a. Check gas pressure and reset
switch.
Field purge timer open (if
applicable).
a. Check for power or replace if
necessary.
3. If the flame safeguard
relay goes into safety
shutdown (lockout).
See technical cut sheet on
flame safeguard relay.
a. Determine the cause of
(lockout). Push reset button on
flame safeguard relay.
4. If pilot does not light after
prepurge has timed out (10-
seconds) and voltage is
present on flame safeguard
output terminals.
Manual pilot shut-off valve
closed.
a. Slowly open valve.
Inlet gas pressure lower than
required gas pressure.
a. Increase gas pressure.
No gas through pilot
regulator with inlet gas
pressure ok.
a. Clear obstruction in vent
orifice/line or replace if
defective.
No gas through pilot
solenoid.
a. Check for correct installation
and voltage. Correct or replace.
Type of gas (natural -LP)
supplied different from
factory required type. Note:
components may change.
a. Replace with factory required
type of gas.
Flame detection system not
sensing pilot flame. (See
spark rod diagram Figure
19).
a. UV sensor - clean lens and
sight tube. Check wiring and
spark plug.
b. Flame Rod - assure rod is in
flame, check wiring and flame
rod.
No voltage on secondary side
of ignition transformer.
a. Check wiring and replace
transformer if correct.
Table 16. Trouble shooting guide for systems with pilot (continued)
Symptom
Probable Cause
Solution
