York R-410A Cooling Sequence Of Operations, Welded Gas Valve Relay Response, Safety Controls

279550-YIM-A-0207

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 de-energizes the induced draft motor (if flame is not present) to attempt to open the pressure switch to de-energize the gas valve. If the pilot or main gas valve is still sensed as energized after the inducer has been off for 5 seconds, the control re- energizes the inducer to attempt to vent the unburned gas. In either case, the control enters a hard lockout. If the pilot or main valve becomes Un-Welded the inducer will de-energize, but the control will remain in a hard lockout.

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 first-stage cooling, the thermostat terminals G and Y1 energize, signaling the compressor, indoor blower and outdoor fan to operate. The indoor blower will operate according to the fan delay profile selected using Table 17.

When the thermostat calls for second-stage cooling the thermostat terminal Y2 energizes, signaling the compressor bypass ports to close and the indoor blower to increase speed. If the outdoor fan motor has an ECM controller, Y2 will also signal the motor to increase speed.

When the thermostat is satisfied, terminals G, Y1 and Y2 are de-energized, thus stopping operation of the compressor and outdoor fan. The indoor blower will remain on according to the fan delay profile selected using Table 17.

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 R-410A systems. R-22 pressure switches must not be used as replacements for the R-410A pressure switches.

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