7
White-Rodgers Integrated Furnace Controls – 50A50 & 50A51 Series
Fan On
When the thermostat fan switch is in the ON position,
24V AC is applied from the thermostat “G” terminal
to the I.F.C. Control “G” terminal.
The “G” call to the I.F.C. control will cause it to energize
an internal relay coil. This relay’s switch will close,
energizing the indoor blower.
On single stage controls, the blower will run on
Heating Speed. On Two-Stage I.F.C. controls, the
blower will run on the low Heating Speed. On
Variable-Speed models, the “G” call to the blower
motor will signal it to run at 50% of the programmed
cooling CFM speed.
Cooling Air Flow
When the thermostat system switch is in the COOL
position and the thermostat calls for cooling, 24V AC
is applied from the thermostat “Y” terminal to the
I.F.C. Control “Y” terminal.
The “Y” call to the I.F.C. Control will cause it to
energize an internal relay coil. This relay switch will close
energizing the indoor blower on the cooling speed tap.
The I.F.C. control’s fan speed relays are inter-locked to
prevent power from being applied to two blower motor
speed taps at the same time. On Variable-Speed models,
the “Y” call to the blower motor will signal it to run at
80% of the programmed cooling CFM Speed. Note:
Y and BK must be jumper or humidistat connected to
BK to get 100%.
If the “Y” connection is not made to the Control,
the indoor blower will run on heating speed during a
cooling cycle.
Cooling Blower Delay to Off
The Control provides an optional indoor blower off
delay of 80 seconds in cooling cycles. The off delay is
field selectable by adjusting Dip-Switch 1 to OFF
except 50A50-571 Control. A jumper wire must be cut.
Dip-Switch 1 must be in the ON position always on
variable speed furnace models using 50A51-505/-506/-507
Controls. See Furnace ECMTM2 Motor Operation.
The White-Rodgers Integrated Furnace Control (I.F.C.)
is an automatic ignition control module that uses
microcomputer based circuitry to continuously monitor,
analyze and control the proper operation of the gas
burner, induced draft motor and indoor blower. The
microcomputer provides continuous surveil-lance of
the thermostat, flame sensor and safety devices to
initiate automatic gas burner ignition and shutoff
sequences during normal, or fault condition operation.
There are currently several versions of the White-Rodgers
50A50/50A51 Integrated Furnace Controls:
1. 50A50 Series -405 Single-Stage controls are used in
✽UD/✽DD-C-A, B and FCA/FUA-A-A.
2. 50A50 Series -406 Single-Stage controls are used in
✽UC/✽DC-A & B and ✽UX/✽DX-C-A.
3. 50A50-471 and 473 Single-Stage used in ✽UD-C-H
and ✽DD-C-C.
4. 50A50-472 and 474 Single-Stage used in ✽UC/
✽DC-C-C.
5. 50A50-571 Single-Stage used in ✽UE/✽DE-A-K,
FUA- and FCA-E and is part of the up-grade
control system for Radiant Sense Controls,
Part No. KIT 3793.
6. 50A51 Series -405 or -495 Two-Stage used in
✽UD/✽DD-R.
7. 50A51-506 Two-Stage Variable-Speed used in
✽UD/✽DD-R9V. 50A51-505 superseded by 50A51-506
after October 1995.
8. 50A51-506 Two-Stage Variable-Speed used in
✽UY/✽DY-R9V.
9. 50A51-507 Two-Stage Variable-Speed used on all
Variable-Speed models after September 1996.
✽First letter may be A or T or F
Note: Control models 50A50-406/472 and 474 and
50A51-405/-495/-505/-506/-507 provide on-board
relay switching of 120V AC system power for the
optional humidifier and electronic air cleaner accessories.
Control models 50A50-471/473 provides on-board
relay switch-ing of system power for the optional
humidifier accessory only.
During heating cycles, the Control provides on-board relay
switching of 120V AC system power for the
induced draft motor, hot surface ignitor and 24V AC power
for the gas valve. During heating and cooling cycles, the
Control provides on-board relay switching of system power
for the indoor blower motor.
