OPERATION
HEAT MODE
Output
Standb
y
Call f
or Heat
Self-Chec
k
Pre-Pur
g
e
Ignitor W
arm-up
(Adaptive
, star
ts
at 17s)
Ignition Activ
ation
P
eriod
Blo
wer Heat ON
Dela
y (*Default)
Heating until
Thermostat
is Satisfied
P
ost-Pur
g
e
Blo
wer Heat Off
Dela
y (*Default)
Standb
y
15 s
5-21 s
2.8 s
25, *60 s
15 s
90, *120, 150, 180 s
Thermostat - W
Inducer
Pressure Switch
Ignitor
Gas Valve
Flame Sensor
Blower (Heat Speed)
Humidifier (24V)
Humidifier (120V)
EAC
LED
On
Amber LED - 42 Flash
Green LED – Solid On
Cool On Delay
• Cool blower ON delay is 2 seconds.
Fan & Low Cool
• The constant fan speed (G) and low cool speed
(Y1) are determined by the fan speed tap selected
with dipswitch SW1-2 (heat speed is default).
• There is a 1 second blower ON delay and a 1
second blower OFF delay for a fan only demand.
• Set thermostat to Fan ON for continuous fan.
Dehumidification
NOTE:
This feature requires connection to a thermostat
with a dehumidification function (DHUM terminal).
• DHUM input is reverse logic in that presence of a
24V signal = no dehumidify demand, and absence
of a 24V signal = dehumidify demand.
• Dehumidify demand with a Y1 input runs the blower
at the low cool speed selected by dipswitch SW1-2
(heat speed is default).
• Dehumidify demand with a Y / Y2 input runs the
blower at the cool speed for 10 minutes, then
reduces the blower speed from cool to low cool
for 10 minutes, then returns to the cool speed for 10
minutes.
• Alternating 10-minute cycles continue for as long as
there is a call for 2
nd
Stage cooling (Y2).
• When the call for cool is satisfied and there is a
dehumidify demand, the blower off delay is reduced
to 5 seconds.
Air Conditioner & Heat Pump
• Systems retrofitted with 50M56U-751 can be paired
with either a 1 or 2 stage air conditioner or heat
pump.
• When paired with a 1-stage unit, connect the Y
output from the thermostat to Y/Y2 input on the
control. For 2-stage units, connect the Y1 output
from the thermostat to the Y1 input on the control
and the Y2 output from the thermostat to the Y/Y2
input on the control.
• 50M56U-751 will provide auxiliary heating during
a heat pump defrost cycle if it receives heat and
cool calls simultaneously (W + any Y).
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