White Rodgers 50A66-743 User Manual

2

ELECTRICAL RATINGS [@ 77°F (25°C)]:
  Input Voltage: 25 VAC 50/60 Hz
 Max. Input Current @ 25 VAC: 0.45 amp
    Relay Load Ratings:

Valve Relay:  1.5 amp @ 25 VAC 50/60 Hz 0.6 pf
Ignitor Relay:  2.0 amp @ 120 VAC 50/60 Hz
 (resistive)
Inducer Relay:  2.2 FLA–3.5 LRA @ 120 VAC
Circulator Relay: 14.5 FLA–25.0 LRA @ 120 VAC

Minimum current to insure flame detection: 0.25 µa DC*
Maximum current for non-detection: 0.1 µa DC*
Maximum allowable leakage resistance: 100 M ohms

*Measured with a DC microammeter in the flame probe lead

OPERATING TEMPERATURE RANGE:
  -40° to 175°F (-40° to 80°C)
HUMIDITY RANGE:
  5% to 93% relative humidity (non-condensing)
MOUNTING:
  Surface mount multipoise
Timing Specs: (@ 60 Hz**)

 

Flame Establishing Time: 

0.8 sec

Flame Failure Response Time: 

2.0 sec

**  At 50 Hz, all timing specifications should be increased 

by 20%

Gases Approved: Natural, Manufactured, Mixed, Liquified 
Petroleum, and LP Gas Air Mixtures are all approved for use.

Pre-Purge

The period of time intended to allow for the dissipation of any unburned 
gas or residual products of combustion at the beginning of a furnace 
operating cycle prior to initiating ignition

15

Trial for Ignition 
Period (TFI)

The period of time between initiation of gas flow and the action to 
shut off the gas flow in the event of failure to establish proof of the 
supervised ignition source or the supervised main burner flame.

4

Ignition Activation 
Period (IAP)

The period of time between energizing the main gas valve and 
deactivation of the ignition means prior to the end of TFI

4

Retries

The additional attempts within the same thermostat cycle for ignition 
when the supervised main burner flame is not proven within the first 
trial for ignition period.

4 times

Valve Sequence 
Period

Valve sequence period equals 4 seconds trial for ignition period x 
(1 initial try + 2 retries) + 12 seconds.

20

Interpurge

The period of time intended to allow for the dissipation of any unburned 
gas or residual products of combustion between the failed trial for 
ignition and the retry period.

15

Post-Purge

The period of time intended to allow for the dissipation of any unburned 
gas or residual products of combustion at the end of a furnace burner 
operating cycle. Post-purge begins at the loss of flame sense.

5

Lockout Time

ANSI standard rated module timing.

250

Heat Delay-To-Fan-On

The period of time between proof of the supervised main burner flame 
and the activation of the blower motor at Heat speed.

45

Heat Delay-To-Fan-Off*

The period of time between the loss of a call for heat and the 
deactivation of the blower motor at Heat speed.

60/

90/120/180

Cool Delay-To-Fan-On

The period of time after a thermostat demand for cool before energizing 
the circulator blower motor at Cool speed.

2

Cool Delay-To-Fan-Off*

The period of time between the loss of a call for cool and the 
deactivation of the blower motor at Cool speed.

2/

Ignitor Warm-up

The length of time allowed for the igniter to heat up prior to the initiation 
of gas flow.

20

Auto Reset

After one (1) hour of internal or external lockout, the control will auto-
matically reset itself and go into an auto restart purge for 60 seconds.

60 minutes

Humidifier

Yes

Electronic Air Cleaner

Yes

*This time will vary depending on option switch position. The control is factory set at 90 seconds HEAT 

delay-to-fan-off and 45 seconds COOL delay-to-fan-off. See OPERATION section for further information.