White Rodgers 50A55-3797 Installation Manual download pdf (Page 5)

OPERATION

OPTION SWITCHES

The option switches on the 50A55-3797 control are used

to determine the length of the heat delay-to-fan-off periods

and cool delay-to-fan-off period. The following tables

shows the time periods that will result from the various

switch positions.

HEAT MODE

In a typical system, a call for heat is initiated by closing the

thermostat contacts. This starts the 50A55 control’s heating

sequence. The inducer blower and optional humidiﬁer are

energized and the ignitor is powered.

This controller has an adaptive algorithm that adjusts

the duration of the ignitor warm-up to extend ignitor life.

Upon initial application of power, the warm-up time is 17

seconds. The ignitor on-time will then be increased or

decreased depending on whether or not ﬂame is achieved.

The warm-up time is limited to a maximum of 21 seconds.

During the ﬁrst 64 warm-up periods following power-up,

the warm-up time may not be less than 11 seconds.

Upon a call for heat, if the warm-up time has not been

locked, it will be decreased by one second. This reduction

of the ignitor on-time will continue until ﬂame fails to be

achieved (resulting in a retry).

In the event of a retry, the warm-up time will be increased

by one second and locked in at that duration. Once the

warm-up time is locked, it remains ﬁxed until another call

for heat results in a retry, in which case the warm-up time

is again increased by one second and remains locked.

In the event of two successive retry attempts, the warm-up

time will be unlocked and set to 21 seconds. If ﬂame is then

achieved, the warm-up time will begin adapting again with

the next call for heat. If, however, this third attempt fails

to achieve ﬂame, the control will go into system lockout.

At the end of the ignitor warm-up time, both valves in the

gas valve are opened. Flame must be detected within 4

seconds.

If ﬂame is detected, the delay-to-fan-on period begins. After

the delay-to-fan-on period ends, the optional electronic air

cleaner is energized and the circulator fan is energized at

heat speed. When the thermostat is satisﬁed, 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 5 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

60-second wait following an unsuccessful ignition attempt

(ﬂame not detected). After this wait, the ignition sequence

is restarted with an additional 1 second of ignitor warm-

up time.

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.

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-energize

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.

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 and the compressor. The cool delay-to-fan-on

period begins. After the delay period ends, the optional

electronic air cleaner is 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 delay-to-

fan-off period ends, the circulator fan and electronic air

cleaner (optional) are de-energized.

MANUAL FAN ON MODE

If the thermostat fan switch is moved to the ON position,

the circulator fan (heat 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.

COOL "OFF" DELAY

SW1 SECS.

ON 0*

OFF 80

HEAT "OFF" DELAY

SW2 SW3 SECS.

ON OFF 60

ON ON 100*

OFF ON 140

OFF OFF 180

*Factory Setting

1 2 3 4 5 6 7 8

Comments to this Manuals

No comments

White Rodgers 50A55-3797 Installation Manual Page 5

Comments to this Manuals

Related products and manuals for Thermostats White Rodgers 50A55-3797