Nordyne Downflow Direct Vent Forced Air Gas Oil Furnaces SERIES M1B - Manual (Page 24)

24
Oil Gun Furnace with Honeywell R7184 /
Beckett 7505 Control - M5S Models
1. When a call for heat is initiated, there is a 2
to 6 second delay while the control performs
a safe start check.
2. The ignition and motor are turned on and a
fl ame should establish within a 15-second
lockout time. NOTE: Burner will prepurge for 15
seconds if equipped with Honeywell R7184B
or Beckett 7505B Control.
3. If fl ame is not sensed within the 15-second
lockout time, the control shuts down on safety
lockout and must be manually reset by pushing
the reset button on the control. If control locks
over three times in a row, the control enters
restricted lockout. To reset Honeywell R7184:
Hold down the reset button for 45 seconds
until the LED fl ashes once. Beckett 7505: Hold
down reset button for 15 seconds until the red
LED turns off and the yellow LED turns on.
WARNING:
If furnace still doesn’t light, turn
the furnace off as described above
and call your technician. In the
event of fl ashback or explosion,
immediately shut off furnace and
call your service technician.
4. After fl ame is established, the ignition remains
on for 10 seconds to ensure fl ame stability. It
then turns off.
5. The circulating air blower will energize after
the temperature fan switch closes.
6. The furnace runs until the call for heat is
satisfi ed.
7. The circulating air blower will de-energize when
the temperature fan switch opens.
Gas Gun Models
1. On a call for heat, the furnace control begins
an ignition sequence which lasts approximately
45 seconds.
2. After this sequence, the control module tests
to see if fl ame is sensed. If it has, the furnace
continues to heat until the thermostat is
satisfi ed.
3. If the burner has not lit, the ignition sequence
is repeated a maximum of two more times. If
fl ame is not sensed after three attempts, the
control enters Lockout and no further attempts
to light the burner will occur. If Lockout occurs,
contact a qualifi ed service technician for
assistance.
OPERATING SEQUENCE
Standing Pilot
1 On a call for heat, the thermostat contacts
close, supplying 24 VAC to the gas valve.When
energized, the valve steps open at a reduced
fl ow and opens fully within 14 seconds.
2. When the call for heat is satisfied, the
thermostat contacts open, shutting off gas fl ow.
Standing Pilot w/Induced Draft Blowers
1. On a call for heat, the thermostat contacts
close, supplying 24 VAC to the relay.
2. The relay contacts close and the induced draft
motor energizes.
3. When the inducer starts, the air pressure
switch closes at -0.20 W.C. differential pressure
and energizes the gas valve. The valve steps
open at a reduced fl ow and opens fully after
approximately 14 seconds.
4. When the call for heat is satisfied, the
thermostat contacts open, the gas valve shuts
off gas fl ow, and the induced draft blower stops.
M1M Models with Direct Ignition
1. On a call for heat, the thermostat contacts
close, supplying 24 VAC between terminals
C and W of the control module.
2. When the inducer starts, the air pressure switch
closes at -0.20 W.C. differential pressure and
energizes the gas valve.
3. After a 45 second purge, the ignitor is energized
for a 30 second warm-up period. After warm
up, the gas valve opens. NOTE: The time for
ignition is approximately 6 seconds, after which
the gas valve either remains open if fl ame is
sensed, or closes if fl ame is not sensed.
5. If fl ame is not sensed, the sequence repeats
four more times before a lockout occurs. To
reset, wait 30 seconds and then interrupt the
24 VAC power by turning the room thermostat
below room temperature, then returning it to
the original set point.
6. If fl ame does not establish on the 5th attempt
(initial fi re + 4 re-tries), the control de-energizes
the gas valve, the red LED fl ashes 4 times,
and the furnace locks out heat operation for
1 hour. See Table 9 (page 29).
7. If a fl ame is present, the control energizes the
main blower on heat speed 30 seconds after
the gas valve opens.
8. When call for heat is satisfi ed the thermostat
contacts open, the gas valve shuts off gas fl ow
and the combustion blower remains on for a
30 second post-purge period.
9. The main blower is de-energized after a 120
second blower off delay.