Welded Gas Valve Relay Response.
If either or both Pilot and Main Gas valve outputs are sensed to be off for more than 1 seconds when commanded to be on the control board shuts off all outputs and enters a hard lockout
If the Pilot valve or Main valve output is sensed to be energized for more than 1 second when commanded to be off, the control
During a hard lockout, the control board LED will remain off and the control will not respond to any thermostat demands.
The only way to recover from a hard lockout is to remove and then reapply 24VAC power to the control board.
Safety Controls
The control circuit includes the following safety controls:
1.Limit Switch (LS) - This control is located inside the heat exchanger compartment and is set to open at the temperature indicated in the Temperature Controls Table of the unit wiring diagram. It resets automatically. The limit switch operates when a high temperature condition caused by inadequate supply air flow occurs, thus shutting down the ignition control and closing the main gas valve and energizing the blower.
2.Pressure Switch (PS) - If the draft motor should fail, the pressure switch prevents the ignition controls and gas valves from being energized.
3.Flame Sensor - The flame sensor and controls are located per Proper Flame Adjustment Figure 19. If an ignition control fails to detect a signal from the flame sensor indicating the pilot flame is properly ignited, then the main gas valve will not open.
4.Rollout Switch (RS) - This switch is located in the burner vestibule. In the event of a sustained main burner flame rollout, it shuts off the ignition control and closes the main gas valve.
NOTE: The manual reset Rollout Switch (RS) must be reset before allowing furnace operation.
5.Auxiliary Limit Switch (ALS) - This control is located inside the heat exchanger compartment and is set to open at 160°F. It is a manual reset switch. If ALS trips, then the primary limit (LS) has not functioned correctly. Replace the primary limit LS.
Table 18: Ignition Control Board FLASH CODES
Flash Code | Description |
On Steady | Control Failure - Replace Control |
Heart Beat | Normal Operation |
1 Flash | Not Applicable |
2 Flashes | Pressure / Centrifugal Switch Open with Inducer On |
3 Flashes | Pressure / Centrifugal Switch Closed with Inducer Off |
4 Flashes | Not Applicable |
5 Flashes | Lock Out From Too Many Flame Losses |
6 Flashes | High Temperature Switch Open (Primary or Aux.) |
7 Flashes | Rollout Switch Open |
8 Flashes | Flame Present With Gas OFF |
Cooling Sequence Of Operations
When the thermostat calls for
When the thermostat calls for
When the thermostat is satisfied, terminals G, Y1 and Y2 are
Safety Controls
The control circuit includes the following safety controls:
1.High Pressure Switch (HP)- This switch protects against excessive discharge pressures due to a blocked condenser coil or a condenser motor failure (opens at 625
± 25 psig and resets at 500 ± 25 psig).
2.Low Pressure Switch (LP)- This switch protects against loss of refrigerant charge (opens at 7 ± 3 psig and resets at 22 ± 5 psig).
The above pressure switches are specifically designed to operate with
The ability to properly perform maintenance on this equipment requires certain expertise, mechanical skills, tools and equipment. If you do not possess these, do not attempt to perform any maintenance other than those procedures recommended in this Installation Manual. Failure to heed this warning could result in serious injury and possible damage to this equipment.
24 | Unitary Products Group |
