33
SYMPTOMS
POSSIBLE CAUSE(S)
CORRECTIVE ACTION
N. High limit is tripping.
O. Power ventor will not run.
P. Power ventor turns on
and off during operation.
Q. Power ventor will not stop.
R. Noisy power ventor.
1. Unit is over fi red.
2. Incorrect
airfl
ow.
3. Defective high limit switch.
4. Defective control board.
1. No power supply to the unit.
2. Thermostat not calling.
3. Loose wiring or connection.
4. Motor overload protection is tripping
or bad motor.
5. Defective control board.
6. Motor not oiled.
1. Power ventor improperly wired.
2. Motor overload cycling or defective
motor.
3. Defective control board.
4. Motor not oiled.
1. Power ventor improperly wired.
2. Main burner did not light on call for
heat.
3. Defective control board.
1. Power ventor wheel loose.
2. Power ventor wheel is dirty.
3. Power ventor wheel is rubbing on
housing.
4. Bearings are dry.
1. Refer to “Gas Input Rate” in the
Operation section of this manual.
Check orifi ce size. Replace if too large.
2. See blower manufacturer for
corrective
action(s).
3. Check operation of switch. If switch is
open during operation, check gas
pressure and/or CFM; adjust
accordingly. If switch is open during
start-up, replace switch.
4. Check for 24V on line side of high
limit. Constant voltage should be
recorded. If not, control board is
suspect. Check fl ash code.
1. Turn on power supply, check fuses
and replace if bad.
2. Turn up thermostat. Check for 24V on
terminals R and W1 on terminal strip.
3. Check all wiring in the power vent
circuit to ensure good connection,
including
“neutral.”
4. Check for 115V between motor leads
and check amp draw of motor.
Replace if necessary.
5. Check for continuous 115V on
terminal “CBM Blower” and neutral
during call for heat. If not present and
all checks are normal, replace.
6. Refer to “Maintenance” section of this
manual.
1. Check power ventor circuit per wiring
diagram.
2. Check motor voltage and amp draw
against motor name plate, replace if
motor found defective.
3. Check for continuous 115V on
terminal “CBM Blower” and neutral
during call for heat. If not present
and all checks are normal, replace.
4. Refer to “Maintenance” section of this
manual.
1. Check power ventor circuit per wiring
diagram.
2. Heater is in lockout mode; check fl ash
code table for problem.
3. If no fl ash codes present along with
no call for heat, replace control board.
1. Replace or tighten.
2. Clean power ventor wheel.
3. Realign power ventor wheel.
4. Oil bearing on power ventor motor
(refer to label on motor).
Table 8A – Tubular Duct Furnace Troubleshooting Guide (continued)
