York R-410A Main Burner Operation, Post Purge, Heat Blower Off Delay, Lockout, Rollout Switch

279550-YIM-A-0207

Main Burner Operation

High Heat Warm-up

Two stage models run high heat for the first 60 seconds following Pilot Flame Stabilization period regardless of W2 demand. If W2 is not energized at the end of this 60 second period the control de energizes the high gas output and steps the inducer to low speed. If W2 is energized the control remains on high heat.

There is no high heat warm-up on single stage models.

Low Heat

The control board keeps the pilot gas valve, main gas valve and induced draft motor energized while continuously monitoring the call for heat, low pressure switch, and flame status.

If the call for heat (W1) is lost, the control de-energizes the gas valve and begins post purge.

If low pressure switch opens, the control de-energizes the gas valve and begins pressure switch proving mode.

If flame is lost, the control de-energizes the gas valve within 2.0 second and counts the flame loss. If flame has been lost more than 16 times within the same call for heat, the control board locks out flashing “5” on the LED. If flame has been lost less than 16 times, the control attempts re-ignition after a 300 second inter-purge period.

High Heat

If the W2 terminal was energized more than 1 second before W1 at the start of the call for heat, and remains continuously energized through the call for heat, the control considers it to be connected to a single stage thermostat and implements a 10 minute Auto staging feature. The 2nd stage thermostat call is ignored until 10 minutes into steady heat (9 minutes after high heat warm-up ended).

The control recognizes a call for 2nd stage heat when W2 is energized (connected to “R”). The control energizes the high gas output and induced draft motor on high speed.

If the call for 2nd stage heat goes away and the 1st stage call remains, the control de energizes the high gas valve, drops inducer speed to low, and returns to low heat operation.

Response to loss of W1, low pressure switch, and flame are identical to low heat operation.

Post Purge

The control board runs the induced draft motor for a 30 second post-purge period, and then de-energizes the inducer. If a call for heat occurs during post-purge, the control finishes the post- purge, drops inducer out to re-prove open pressure switch before continuing with the heat cycle.

Heat Blower Off Delay

The control board de-energizes the indoor blower motor after a delay time as selected by movable shunt (60, 90, 120 or 180 seconds). Blower timing begins when the thermostat is satisfied or heat cycle was interrupted. The control returns to standby when the blower off delay is complete.

If the thermostat call for heat returns before the blower off delay is complete, the control begins an ignition sequence with pre- purge while the blower off delay continues.

Lockout

While in lockout, the control board keeps the pilot gas valve, main gas valve and induced draft motor de-energized.

Lockouts due to failed ignition or flame losses may be reset by removing the call for heat (W1) for more than 1 second, but less than 20 seconds, or by removing power from the control for over 0.25 seconds. The control will automatically reset lockout after 60 minutes.

Lockouts due to detected internal control faults will reset after 60 minutes or power interruption.

High Temperature Limit Switch

Any time the high temperature limit switch is open the control board will run the indoor blower motor on heat speed, the inducer (on high speed for 2 stage models), de-energize the gas valve, and flash “6” on the LED. When the high temperature switch closes, the control will restart the ignition sequence beginning with pre-purge.

Rollout Switch

If the rollout switch opens for more than 0.25 seconds, the control board will run the inducer (on high speed for 2 stage models) for a post-purge period, immediately de-energize the gas valve, and flash “7” on the LED. The blower output will be energized during an open rollout condition.

If the rollout switch closes, the control shall remain locked out until power removed or “W” is removed.

Rollout switch lockout shall not reset automatically.

Power Interruptions

Power interruptions of any duration shall not cause lockout or any operation requiring manual intervention.

Flame present with Gas off

If flame is sensed for longer than 4.0 seconds during a period when the gas valve should be closed, the control will enter lockout flashing “8” on the LED. The control will turn on the inducer blower while the flame is present.

Unitary Products Group 23