32
SYMPTOMS
POSSIBLE CAUSE(S)
CORRECTIVE ACTION
1. Tighten all electrical connections.
2. Check for proper air supply across
heat exchanger and proper gas supply.
3. Relocate thermostat away from outside
wall or drafts.
4. Jumper high limit switch wiring (orange
and yellow wires). If burner operating
normally, replace switch.
1. Refer to “Gas Input Rate” in the
Operation section of this manual.
2. Is the unit output sized correctly for
the heat loss of the space? Has the
space been enlarged? Is the unit
located in the space properly (see
“Installation” section of this manual)?
3. Check thermostat circuit; 24V on
terminals “R” and “W” on terminal strip.
4. Check air movement across the heat
exchanger. Check gas input to ensure
unit is not over fi red. Check heat
exchanger to ensure unit is not dirty.
5. Check orifi ce size (refer to “Gas
Input Rate” in the Operation section
of this manual).
6. See blower manufacturer for
corrective
action(s).
1. Refer to “Gas Input Rate” in the
Operation section of this manual.
Check orifi ce size. Replace if too large.
2. Check thermostat for operation, to
ensure circuit open and closes.
3. Check wiring per diagram. Check
operation at the gas valve. Look for
a short in thermostat circuit.
4. Replace valve and check pressure
setting (see “Gas Supply Pressure”
Table in the Pipe Installation section
of this manual).
5. Refer to “Gas Supply Pressure” Table
in the Pipe Installation section of this
manual.
6. See blower manufacturer for
corrective
action(s).
1. Test and reset manifold pressure
(see “Gas Supply Pressure” Table
in the Pipe Installation section of this
manual.)
2. See blower manufacturer for
corrective
action(s).
1. Loose electrical connections at
thermostat or gas valve.
2. Unit cycling on high limit.
3. Thermostat located improperly.
4. Defective high limit switch.
1. Incorrect gas input.
2. Unit
undersized.
3. Thermostat
malfunction.
4. Unit cycling on high limit.
5. Incorrect orifi ce sizes.
6. Incorrect
airfl
ow.
1. Unit is over fi red.
2. Thermostat
malfunction.
3. Unit runs continuously.
4. Defective gas valve.
5. Excessive gas supply pressure.
6. Incorrect
airfl
ow.
1. Incorrect manifold pressure or
gas
input.
2. Incorrect
airfl
ow.
J. Rapid burner cycling.
K. Not enough heat.
L. Too much heat.
M. Cold air is delivered during
heater
operation.
Table 8A – Tubular Duct Furnace Troubleshooting Guide (continued)
