Nordyne Downflow Direct Vent Forced Air Gas Oil Furnaces SERIES M1B - Manual (Page 25)

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4. When call for heat is satisfi ed, the thermostat
contacts open and the gas valve shuts off gas
fl ow.
WARNING:
Should overheating occur, or the gas
supply fails to shut off, shut off the
manual gas valve to the furnace before
shutting off the electrical supply.
AVERTISSEMENT:
En case de température excessive,
ou sail est impossible de cooper
l’alimentation en gaz, fermer le
robinet manuel d’alimentation en gaz
du générateur d’sir chaud avant de
cooper l’alimentation électrique.
FURNACE CONTROLS & FUNCTIONS
Furnace On-Off Switch
This switch turns electrical power to the furnace
on and off. The switch must be set in the ON
position for the furnace to operate. For M1G
models, in warm weather there is a possibility
of the blower turning on periodically or operating
continuously due to a heat buildup within the
furnace by a combination of warm weather and
heat from the pilot. This is normal operation as
long as there is power to the furnace and the
furnace On-Off switch is in the ON position. If
blower operation is not desired, the furnace On-
Off switch may be set in the OFF position to cut
the electrical power to the furnace. See Figure 35.
Limit Control
This furnace is protected by two high temperature
safety limit switches. The auxiliary (upper) limit
switch and the high temperature (lower) limit
switch are automatic reset types. If either limit
trips, the burner will shut off. If either limit switch
trips off again soon after resetting, set the furnace
furnace On-Off switch to the OFF position and
call your authorized serviceman. See Figure 35.
Gas Valve
The gas valves for the gas furnaces are a 100%
shut-off type and will fail safe, if for some reason
the gas is turned off. The valve is a “step-open”
type for M1G models and “slow-open” for M1M
and M1B models which means it opens to a
low-fi re position, and after a few seconds, “steps-
open” to high-fi re.
Roll Out Switch (M1G - 056 & 070)
The furnace is protected by a manual reset safety
switch located on the bottom left hand side of
the combustion pipe.
Oil Burner Primary Control
The primary control for oil gun furnaces starts
the burner, monitors a safe operating cycle, and
shuts the burner off at the end of a heating cycle.
The control uses a light sensing transducer to
determine if fuel ignition has been successfully
attained. If ignition is not attained by the end of
the safety ignition timing period, the control shuts
the burner off and enters “lock-out.” See Figure 35.
Summer Cooling - (B, C, & D Series)
Your furnace is A/C ready, equipped with A/C
relay and transformer. The unit is equipped to
use a 4-wire thermostat. When using a 5-wire
thermostat, RC and RH should be jumped (see
instructions included with thermostat).
Furnace
On-Off
Switch
Oil
Pump
Fan
Control
Lower
Limit
Switch
Upper
Limit
Switch
Oil
Burner
Control
Figure 35. Furnace Controls - Oil Furnace