Справочник Пользователя для White Rodgers 21D83M-843 Replacement Kit for Lennox Single Stage Nitride Ignition

5

The option switches on the 50A66-843 control are used 
to determine the length of the heat delay-to-fan-off and 
cool-delay-to-fan-off periods. The following table shows 
the time periods that will result from the various switch 
positions.

60 sec.

90 sec.*

120 sec.
180 sec.

Off           Off
Off           On
On           Off
On           On

2 sec.

45 sec.*

*Factory Setting

Off
On

In a typical system, a call for heat is initiated by closing the 
thermostat contacts. This starts the 50A66-843 control’s 
heating sequence. The inducer blower and humidifier are 
energized. After a 15-second pre-purge period, the 768A 
Silicon Nitride  ignitor is powered.
This controller has an adaptive algorithm that reduces 
ignitor temperature to slightly greater than the minimum 
temperature required to ignite gas in each particular 
application. The control measures the line voltage and 
determines an initial ignitor temperature setting based 
on the measurement. After each successful ignition, the 
control lowers the ignitor temperature slightly for the next  
ignition attempt. The control continues to lower the ignitor 
temperature until ignition does not occur, and the control 

goes into retry mode. For the second attempt to ignite 
gas within the same call for heat, the control increases 
the ignitor temperature to the value it was on the third 
previous successful ignition. After ignition is successful, 
the control sets the ignition temperature at this value for 
the next 255 calls for heat, after which the control repeats 
the adaptive algorithm. The control is constantly making 
adjustments to the ignitor temperature to compensate for 
changes in the line voltage.
The 80 VAC Silicon Nitride ignitor manufactured by 
White-Rodgers must be used. These ignitors are spe-
cially designed to operate with the 50A66-843's adap-
tive ignition routine to ensure the most efficient ignitor 
temperature.
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 circulator fan is 
energized at heat speed. If there is an optional electronic 
air cleaner on the system, the electronic air cleaner and 
the humidifier are energized. When the thermostat is 
satisfied, the gas valve is de-energized. After proof of 
flame loss, the inducer blower remains energized to purge 
the system for 5 seconds and the delay-to-fan-off period 
begins. 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 50A66-843 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. If this ignition attempt is unsuccessful, three 
more retries will be made before the control goes into 
system lockout.

L1

120 VAC

ACB COOL

COOL

ACB HEAT

HEAT

PARK M1

PARK

PARK M2

PARK

ACC

EAC

120 VAC HOT

LINE

120 VAC TX

XFMR

HTG ACC

HUM

ACB LOW

FAN

Neutral 

120 VAC

Neutral 120 VAC 

Return (5)

Neutral 

120 VAC (5)

Flame Sense

E33

FS

1.  Disconnect all electric power and shut off gas 

supply to the furnace.

2.  Remove the access panel
3.  Disconnect wiring and remove existing ignition 

control board.

4.  Insert the replacement board into existing holes.
5.  Reconnect wiring.
6.  Replace access panel.
7.  Restore the electrical power and gas supply. Refer 

to the furnace installation instructions for start-up 
and check-out procedures.