White Rodgers 50a55-286 Operation Option Switches, Heat Mode, Cool Mode, Manual FAN on Mode

OPERATION

OPTION SWITCHES

The option switches on the 50A55-286 control are used to determine the length of the heat delay-to-fan-off periods. The following table shows the time periods that will result from the various switch positions.

OPTION SWITCH POSITIONS

HEAT delay-	Set switch
to-fan-off:	#1	#2
60 sec.*	On	On
90 sec.	Off	On
120 sec.	On	Off
180 sec.	Off	Off

*Factory set position

HEAT MODE

In a typical system, a call for heat is initiated by closing the thermostat contacts. This starts the 50A55 control’s heat- ing sequence. The inducer blower and optional humidifier are energized and the ignitor is powered.

The ignitor is then allowed to warm up for 17 seconds. The 120 VAC ignitors with a 17 second warm-up time manufactured by Carborundum, Ignitor Systems, Inc., or Norton must be used. These ignitors are specially designed to heat up quickly at a low voltage condition without overheating at a high voltage condition.

At the end of the ignitor warm-up time, both valves in the 36E manifold gas valve are opened. Flame must be detected within 7 seconds.

If flame is detected, the delay-to-fan-on period begins. After the delay-to-fan-on period ends, the optional elec- tronic air cleaner is powered and the circulator fan is energized at heat speed. When the thermostat is satis- fied, the gas valve is de-energized. After proof of flame loss, the heat delay-to-fan-off period begins and the inducer blower remains energized to purge the system for 15 seconds. When the purge is complete, the inducer blower and humidifier are de-energized. After the delay- to-fan-off period ends, the circulator fan and electronic air cleaner are de-energized.

If flame is not detected, both valves are de-energized, the ignitor is turned off, and the 50A55 control goes into the “retry” sequence. The “retry” sequence provides a 15- second wait following an unsuccessful ignition attempt (flame not detected). After this wait, the ignition sequence is restarted with an additional 11 seconds of ignitor warm- up time. If this ignition attempt is unsuccessful, one more retry will be made before the control goes into system lockout.

If flame is detected, then lost, the 50A55 control will repeat the initial ignition sequence for a total of four “recycles”. After four unsuccessful “recycle” attempts, the control will go into system lockout.

If flame is established for more than 10 seconds after ignition, the 50A55 controller will clear the ignition attempt (or retry) counter. If flame is lost after 10 seconds, it will restart the ignition sequence. This can occur a maximum of five times before system lockout.

During burner operation, a momentary loss of power of 50 milliseconds or longer will de-energize the main gas valve. When power is restored, the gas valve will remain de-energized and a restart of the ignition sequence will begin immediately.

A momentary loss of gas supply, flame blowout, or a shorted or open condition in the flame probe circuit will be sensed within 2.0 seconds. The gas valve will de-ener- gize and the control will restart the ignition sequence. Recycles will begin and the burner will operate normally if the gas supply returns, or the fault condition is corrected, before the last ignition attempt. Otherwise, the control will go into system lockout.

If the control has gone into system lockout, it may be possible to reset the control by a momentary power interruption of one second or longer. Refer to SYSTEM LOCKOUT FEATURES.

COOL MODE

In a typical system, a call for cool is initiated by closing the thermostat contacts. This energizes the 50A55 control. The compressor and optional electronic air cleaner are energized, and the circulator fan is energized at cool speed. After the thermostat is satisfied, the compressor is de-energized and the cool mode delay-to-fan-off period begins. After the cool delay-to-fan-off period ends, the circulator fan and electronic air cleaner are de-energized.

MANUAL FAN ON MODE

If the thermostat fan switch is moved to the ON position, the circulator fan (cool speed) and optional electronic air cleaner are energized. When the fan switch is returned to the AUTO position, the circulator fan and electronic air cleaner (optional) are de-energized.

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