Typical Operation - Emerson White-Rodgers 50D50-801 Instructions D'installation

In a typical application, the 50D50-801 is designed to
generate sparks, energize the gas valve and monitor the
flame sensor. It is a 100% shut-off design that locks out
the gas valve if the burner does not light within the safety
time. The ignition sequence begins with a call for heat
from the room thermostat. The thermostat applies power
to the control. After pre-purge interval, the gas pilot valve
is energized and sparks are generated for the selected
safety time. If the burner lights within the allowed period, the
TROUBLESHOOTING
For proper control operation, the control must be electrically
connected to the gas valve with all the ignition wiring
connectors plugged in. Gas valves with an electric "ON/OFF"
switch must have the switch set to "ON".
The light on the control provides a self-diagnosis indication.
If the red light on the module is off continuously, the fault is
likely to be internal to the module. To make sure, interrupt the
24 volt thermostat power for 10 seconds, check program key
installation and then restore. If the internal fault is indicated
again, and flame sensor is not shorted to ground, replace the
control. A flashing light indicates the problem is most likely in
the external components or wiring (see chart below). Proceed
as follows:
Visual checks
1) After the purge delay (if applicable) the pilot valve opens
and the ignition (sparks) starts
2) The pilot burner flame will light
3) The ignition (sparks) stops and the main valve opens
4) The main burner flame will ignite
Troubleshooting the system consists of checking for these
visual indications. Table 4 defines the proper action if any of
these indications does not occur.
Table 3
Pre-Purge Safety Time
30 Seconds 90 Seconds Maximun
Time
Outputs
Thermostat
"TH"
Pilot Valve
Ignitor
Pilot Flame
Sensed
Main Valve
Main Flame
Sensed
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TYPICAL OPERATION

pilot gas valve will remain open and the main valve will be
energized until the call for heat is satisfied. If the burner does
not light, the control will either continuously retry after the
reset time or make two more ignition retries depending on the
options selected. The control can be reset from lockout by
cycling the thermostat to remove power for a minimum of 10
seconds. It includes a system analysis/troubleshooting LED
that indicates normal operation, lockout, or control fault.
Table 4
Error/Condition
LED Flashesash
Check flame probe and wiring. Unit is
False flame
seeing a flame signal with valve closed.
signal
1 Check for poor burner ground wiring
2
No Flame Detected
Check gas supply and pressure to valve.
3
Safety Drive Fault
There is an internal fault with the Pilot
4
PV Drive Fault
There is an internal fault with the Main
5
MV Drive Fault
Check for short between TH and MV.
On
Normal Operation
Off If power is present and LED is not lit,
Control failure
Comments/Troubleshooting
Check for partial shorting on flame
probe wiring
Burner has failed to light after
permitted attempts.
Check sparks and wiring as above.
There is a fault in the internal safety
relay drive.
Check supply voltage is within the
specified range.
If it is, replace control.
Valve relay.
Check for short between TH and PV.
If no external cause, replace control
Valve relay.
If no external cause, replace control
No fault
Verify power to the control.
replace control.