24
The furnace is equipped with a multi-speed motor. Refer
to the furnace wiring diagram,
&
for blower speed selection.
Burner Adjustments
Burner settings are made at the factory. However, these
settings may change during shipping, handling, and
installation. The following items should be checked and
readjusted if necessary.
Gas Pressure
The gas pressure can be checked with a manometer at
the pressure tap (
) located on the
top of the gas valve. The gas valve pressure regulator
can be adjusted by removing the regulator selector stack
and turning the slotted insert located directly under the
selector stack. The regulator selector stack must be
secured in place before each pressure reading is taken.
Natural gas manifold pressure should be 3.5” W.C. and
L.P. gas manifold pressure should be 10” W.C. Replace
the gas pressure tap plug on the gas valve.
Combustion Air
cautIon:
• combustion air adjustment must be made
only by a qualified technician. Improper air
adjustment may cause unsafe operation,
explosion and/or fire asphyxiation.
• If the input to the furnace is too great because
of excessive gas pressure, wrong size nozzle or
orifice, high altitude, etc., the burner flame will
be sooty and can produce carbon monoxide,
which could result in unsafe operation,
explosion and/or fire or asphyxiation.
In order for the flame to burn efficiently, it must receive
adequate combustion air. The amount of combustion air
required varies according to altitude, actual B.T.U. content
of the fuel, gas pressure, conversion to another gas and
other factors. The burner flame should be observed and
any necessary adjustments made before the furnace is
5. Wait 10 minutes to clear out any gas.
If you smell gas,
stoP! and follow the safety information
. If gas is
not detected, proceed to the next step.
6. Set the
furnace on-off
switch to the
ON
position.
• Honeywell: turn knob on gas control counter clockwise
to
ON
.
• Robertshaw: push the gas control lever to
ON
.
7. Turn electric power to the appliance ON.
8. Set the thermostat to
HEat
and/or the desired
temperature setting. The furnace should light in
approximately 45 seconds. If the appliance will not
operate, follow the instructions
and call your service technician or gas
supplier.
In the event of any flashback or explosion, immediately
shut off the furnace and call your service technician.
How to Shut Off Gas - Oil & Gas Gun
1. Set the thermostat to the lowest setting.
2. Turn off all electric power to the appliance at the breaker
or fuse box.
3. Set the thermostat MODE switch to
OFF
.
4. Turn the gas valve OFF:
•
Honeywell: push in and turn the gas control knob
clockwise to the OFF position (
).
•
Robertshaw: push the gas control lever to the OFF
position (
).
5. Replace the furnace door.
notE:
M1B gas gun furnaces may be converted to oil
gun in the field by using the proper conversion kit listed
in the Replacement Parts List available online.
Verifying & adjusting temperature Rise
Confirm the temperature rise through the furnace is
within the limits specified on the furnace rating plate. Any
temperature rise outside the specified limits could result
in premature failure of the heat exchanger.
1. Place thermometers in the return and supply air stream
as close to the furnace as possible. To avoid false
readings, the thermometer on the supply air side must be
shielded from direct radiation from the heat exchanger.
2. Adjust all registers and duct dampers to the desired
position and run the furnace for 10 to 15 minutes in
high fire before taking any temperature readings. The
temperature rise is the difference between the supply
and return air temperatures.
For typical duct systems, the temperature rise will fall
within the limits specified on the rating plate with the
blower speed at the factory recommended setting. If
the measured temperature rise is outside the specified
limits, it may be necessary to change the speed of the
blower.
notE:
Lowering the blower speed increases the
temperature rise and a higher blower speed will decrease
the temperature rise.
Table 7
Table 7. Factory combustion air settings
MoDEl
NAT. GAS
lP Gas
OIL
66,000
3.5
3.5
3.5
86,000
5.3
6
5
