Operation - White Rodgers 50M56U-751 Installation Instructions Manual

Carrier single stage hsi integrated furnace control kit
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OPERATION

CHECK-OUT AND SELF TEST
The 50M56U-751 is equipped with a self test routine used
during the control's installation. The self test checks the
functionality of the control, Inducer, Ignitor, and blower to verify
they are in proper working order. To initiate self test sequence,
ensure thermostat is turned OFF or thermostat wires are
disconnected.
To enter self test:
● Turn on power and manually close blower door switch.
● Wait for 5 seconds.
● Slowly double click select button within 3 seconds.
Sequence is as follows:
● LED will flash 4 times then turn ON inducer motor.
● Ignitor will turn ON for several seconds, then OFF.
● Blower motor – HEAT speed will turn ON a few seconds.
● Blower motor – COOL speed will then turn on for several
seconds.
● Blower and Inducer will turn off followed by a solid LED.
NOTE
The self test functionality is available after power up and
until a Solid LED is present. During this time, the control
will ignore all active calls. If a Solid LED is present,
disconnect power for 10 seconds and refer above to enter
self test routine.
● Repair, replace or service any component that does not
work properly during the self test. The gas valve is not
energized during self test.
● Turn power off.
● Release blower door switch.
● Connect thermostat wires.
● Make appropriate option switch selections
● Install access doors.
● Turn power back on.
● Turn on gas supply to furnace.
● Run unit through one complete call for heat cycle.
OPTION SWITCHES
The option switches on the 50M56U-751 control are used to
determine the length of the heat delay-to-fan-off, heat delay-
to-fan-on and cool delay-to-fan-off periods. The following
illustration shows the options and the selections of the switch
positions. The switches are shown in the factory default
positions.
HEAT OFF
90 SEC
HEAT ON
25 SEC
COOL OFF
5 SEC
*Default for most controls
HEAT MODE
When heat is required, the thermostat will send a call for heat
to the control. This starts the control's heating sequence. The
ignitor and humidifier (optional) are powered. The ignitor is
powered after the pre-purge period.
Upon initial application of power, the ignitor warm-up time is 17
seconds. The ignitor on-time will then be increased depending
on whether or not flame is achieved. The warm-up time is
limited to a maximum of 19 seconds. During the first 64 warm-
up periods following power-up, the warm-up time may not be
less than 17 seconds.
6
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 19 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.
After the ignitor warm-up period, MV LO is energized for the
gas valve. Flame must be detected within 4 seconds. If flame is
detected, the 30-second HEAT delay-to-fan-on period begins.
The circulator and electronic air cleaner (optional) will also
energize at this time.
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 25 seconds. When the purge is complete, the inducer blower
is 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, the valve is de-energized, the ignitor
is turned off, and the 50M56U-751 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 50M56U-751 controller will clear the ignition attempt (or
retry) counter. If flame is lost after 10 seconds, it will re-cycle
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.
120 SEC*
In a typical system, a call for cool is initiated by closing the
60 SEC*
thermostat contacts. This energizes the 50M56U-751 control
90 SEC*
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.
If the thermostat fan switch is moved to the ON position, the
circulator fan (low 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 MODE
MANUAL FAN ON MODE

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