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Secondary Limit Control
The secondary limit control is located on the top of the
blower scroll assembly. This control opens when elevated
temperatures are sensed. Elevated temperatures at the
control are normally caused by blower failure.
If the power to the unit is interrupted during the heating
cycle, it may cause the secondary limit to trip. Once the
blower compartment temperature drops below the limit
reset temperature, the limit will automatically reset.
Back of Unit
Secondary Control Limit
Pre-Operation Checks
1. Close the manual gas valve external to the unit.
2. Turn off the electrical power supply to the unit.
3. Set the room thermostat to its lowest possible setting.
4. Remove the heat exchanger door on the side of the
unit by removing screws.
5. This unit is equipped with an ignition device which
automatically lights the main burner. DO NOT try to
light burner by any other method.
6. Move the gas control valve switch to the OFF
position. Do not force.
7. Wait five minutes to clear out any gas.
8. Smell for gas, including near the ground. This is
important because some types of gas are heavier
than air. If you have waited five minutes and you do
smell gas, immediately follow the warnings on page
4 of this manual. If having waited for five minutes and
no gas smell is noted, move the gas control valve
switch to the ON position.
9. Replace the heat exchanger door on the side of the
unit.
10. Open the manual gas valve external to the unit.
11. Turn on the electrical power supply to the unit.
12. Set the thermostat to desired setting.
Secondary
Control Limit
Open to
Atmosphere
Pressure Boss
Inlet
Pressure Boss
White-Rodges Model 36G54 connected to Manometer
Gas Supply And Manifold Check
Gas supply pressure and manifold pressure with the
burners operating must be as specified on the rating plate.
NOTE: Use adapter kit #0151K00000S to measure gas
pressure on White-Rodgers 36G54 gas valves.
Gas Inlet Pressure Check
Gas inlet pressure must be checked and adjusted in
accordance to the type of fuel being consumed.
With Power And Gas Off:
1. Connect a water manometer or adequate gauge to
the inlet pressure tap of the gas valve.
Inlet gas pressure can also be measured by
removing the cap from the drip leg and installing a
predrilled cap with a hose fitting.
With Power And Gas On:
2. Put unit into heating cycle and turn on all other gas
consuming appliances.
INLET GAS PRESSURE
Natural
Propane
Min 11.0" W.C., Max 13.0" W.C.
NOTE: Inlet Gas Pressure Must be within the Minimum
and Maximum Value Shown in the Inlet Gas Pressure
chart.
If operating pressures differ from above, make necessary
pressure regulator adjustments, check piping size, etc.,
and/or consult with local utility.
Manifold Pressure Check
1. Turn OFF gas to furnace at the manual gas shutoff
valve external to the furnace.
2. Turn off all electrical power to the system.
3. Back outlet pressure test screw (inlet/outlet pressure
boss) out one turn (counterclockwise, not more than
one turn).
4. Attach a hose and manometer to the outlet pressure
15
High Fire Regulator
Outlet
Adjust
High Fire
Coaxial Coil
Coil Terminal (HI)
Terminal (M)
On/O Switch
Common
Terminal (C)
Min 5.0" W.C., Max 10.0" W.C.
Regulator
Vent
Low Fire
Regulator Adjust
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