SERVICING
4.Check the continuity of the thermostat and wiring. Repair or replace as necessary.
ResistanceHeaters
1.Set room thermostat to a higher setting than room temperature so both stages call for heat.
2.With voltmeter, check for 24 volts at each heater relay. Note: BBA/BBC heater relays are DC voltage.
3.No voltage indicates the trouble is in the thermostat or wiring.
4.Check the continuity of the thermostat and wiring. Repair or replace as necessary.
NOTE: Consideration must be given to how the heaters are wired (O.D.T. and etc.). Also safety devices must be checked for continuity.
S-3B COOLING ANTICIPATOR
The cooling anticipator is a small heater (resistor) in the thermostat. During the "off" cycle, it heats the bimetal
element helping the thermostat call for the next cooling cycle. This prevents the room temperature from rising too high before the system is restarted. A properly sized anticipator should maintain room temperature within 1 1/2 to 2 degree range.
The anticipator is supplied in the thermostat and is not to be replaced. If the anticipator should fail for any reason, the thermostat must be changed.
S-3C HEATING ANTICIPATOR
The heating anticipator is a wire wound adjustable heater which is energized during the "ON" cycle to help prevent overheating of the conditioned space.
The anticipator is a part of the thermostat and if it should fail for any reason, the thermostat must be replaced. See the following tables for recommended heater anticipator setting in accordance to the number of electric heaters installed.
Troubleshooting Encoded Two Stage Cooling Thermostats Options
T
E
S
T
INPUT
FROM
THERMOSTAT
POWER
TO
THERMOSTAT
TEST | FUNCTION | SIGNAL OUT | SIGNAL FAN |
INDICATION |
|
|
|
|
|
|
|
S1 + | LOW SPEED COOL | YCON + | Y1 |
* S1 - * | * LO SPEED COOL * | * YCON - * | * Y / Y2 HI * |
S1 + - | HI SPEED COOL | YCON + - | Y / Y2 |
S2 + | LO SPEED HEAT | W1 HEATER | W / W1 |
S2 - | O | ED - | O |
|
| ( FUTURE USE ) |
|
S2 + - | LO SPEED HEAT | W1 HEATER | W / W1 |
| HI SPEED HEAT | W2 HEATER | EM / W2 |
S3 + | G | NONE | G |
* S3 - * | N/A | N/A | N/A |
|
|
|
|
* S3 + - * | N/A | N/A | N/A |
R + - | 24 VAC | R TO T'STAT | R |
|
|
|
|
COM | GND | COM TO T'STAT | C1 , C2 |
*ERROR CONDITION ( DIODE ON THERMOSTAT BACKWARDS )
SEE NOTE 3
SEE NOTE 3
*ERROR CONDITION ( S3 CAN ONLY READ + )
*ERROR CONDITION ( S3 CAN ONLY READ + )
NOTES:
1.) THE TEST SPADE CAN BE CONNECTED TO ANY OTHER TEST SPADE ON EITHER BOARD.
2.) THE + LED WILL BE RED AND WILL LIGHT TO INDICATE + HALF CYCLES. THE - LED WILL BE GREEN AND WILL LIGHT TO INDICATE - HALF CYCLES.
BOTH RED AND GREEN ILLUMINATED WILL INDICATE FULL CYCLES DENOTED BY +
3.) SIGNAL OUT CONDITION FOR W1 , W2 HEATER WILL BE AFFECTED BY OT1 PJ4 AND OT2 PJ2 JUMPERS AND OUTDOOR THERMOSTATS ATTACHED. THE TABLE ABOVE ASSUMES OT1 PJ4 IS REMOVED AND OT2 PJ2 IS MADE WITH NO OUTDOOR THERMOSTATS ATTACHED.
The chart above provides troubleshooting for either version of the encoded thermostat option. This provides diagnostic information for the GMC
A test lead or jumper wire can be added from the test terminal to any terminal on the
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