30 G6RA, G6RK Service Manual
Roll Out Limit Control (See Figure 36)
The function of a roll out switch is to sense any flames
backing out of the heat exchanger tubes. They are normally
closed and are manually reset.
Check-out Procedure:
1. Shut off power supply to furnace.
2. Remove wires from roll out switch.
3. Using an ohmmeter, check out continuity across switch.
4. An infinite reading indicates an open switch.
5. Depress reset button to reset switch.
6. Continuity or 0 ohms should now be read. If not, replace
switch.
Possible causes of roll out switches tripping:
1. Blocked heat exchanger (sooted)
2. Loose heat exchanger tube
3. Burner misaligned
4. Supply air interfering with flame patterns
5. Overfiring/too high gas pressure
6. Insufficient combustion air
Draft Inducer Motor (See Figure 37.)
All models use an induced draft combustion blower mounted
on the outlet of the heat exchanger. Its purpose is to establish
a draft (flow) through the heat exchanger, to insure that all flue
products are carried outside the structure via the vent pipe.
(See Figure 40.) The blower is driven by a 115V permanent
split capacitor motor. The same (part #) blower is used on all
models of all series.
Check-out Procedure:
1. Disconnect Molex plug between control board and motor.
2. Using the appropriate scale on a volt meter, insert probes
into plug coming from control board.
3. Establish call for heat.
4. If voltage is read, check fan capacitor. If fan capacitor is
okay, replace motor. (See Figure 38.)
5. If no voltage is read, replace control.
6. Check for debris in wheel preventing it from turning.
Figure 37.
Figure 38.
Figure 39.
Figure 36.
Pressure Switch
The pressure switch verifies that the inducer is drawing the
combustion gases through the heat exchanger. (Figure 39.)
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