Operating Your Furnace
Care
– 13
Start-Up Procedure
Start the furnace
using the procedures in the section “Operating
Your Furnace
”.
WARNING:
Danger of bodily injury or death. L.P.
Gas is heavier than air and it will settle in any low
area, including open depressions and it will remain
there unless the area is ventilated.
Never attempt to start-up the unit before thoroughly
ventilating the area.
Check the furnace operation as outlined in the following
instructions.
CHECK GAS INPUT AND PRESSURES
For furnaces located at elevations between sea level and 2,000
feet, the measured input must not be greater than the input shown
on the rating plate of the furnace. For elevations above 2,000 feet,
the measured input must not exceed the input on the rating plate
reduced by 4
percent for each 1,000 feet that the furnace is above
sea level.
Gas supply pressure and manifold pressure with the burners
operating is specified on the rating plate.
Rated input will be obtained on a heating value of 2,500 Btu/hr. for
propane at 10-inches manifold pressure with factory-sized
orifices. If L.P. Gas having a different heating value is supplied,
orifices must be changed by a qualified service technician before
the furnace is operated.
CHECK THERMOSTAT
Check the thermostat operation. When set above room
temperature shown on the thermostat, the main burner should
light. Make certain the thermostat turns off the furnace when the
room temperature reaches the selected setting and starts the
furnace when the room temperature falls a few degrees.
CHECK THE MANIFOLD GAS PRESSURE
A tapped opening is provided in the gas valve to facilitate
measuring the manifold gas pressure. A "U Tube" manometer
having a scale range from 0 to 12-inches of water should be used
for this measurement. The manifold pressure must be measured
with the burner and pilot operating. Any major changes in flow
must be made by changing the size of the burner orifice.
Check with your local gas supplier for proper orifice sizing.
CHECK THE GAS INPUT (NATURAL GAS ONLY)
WARNING:
Natural gas heating value (Btu per
cubic foot) can vary significantly. Therefore, it is
the installer's responsibility to see that Btu/hr. input
to the furnace is adjusted properly. Failure to do so
could
cause
combustion
chamber
failure,
asphyxiation, fire or explosion resulting in damage,
bodily injury or death. Refer to the National Fuel
Gas Code (NFPA 54) to be sure the furnace is
burning fuel at the proper rate.
Under
firing
could
cause
inadequate
heat,
excessive
condensation or ignition problems. Over firing could cause
sooting, flame impingement or overheating of the combustion
chamber.
Before starting natural gas input check, obtain heating value of
the gas (Btu per cubic foot) at standard conditions from your local
supplier.
To measure the input, using the gas meter, proceed as follows:
1. Turn off gas supply to all other appliances except the furnace.
2. With the furnace operating, time the smallest dial on the meter
for one complete revolution. If this is a 2-cubic-foot dial, use
the time in seconds as is (3,600 = Sec/hr.). Divide the seconds
by 2 if it is a 1-cubic-foot dial. This gives the seconds per cubic
foot of gas being delivered to the furnace.
3. Assuming natural gas with a heating value of 1,000 Btu per
cubic foot and 34-seconds per cubic foot used as determined
by step (2), then:
Input = 1,000 x 3,600 / 34 = 106,000 Btu/hr.
This measured input must not be greater than the input
indicated on the nameplate of the furnace.
4. Relight all other appliances turned off in Step 1 above. Be
sure all pilots are operating.
Type of Gas
Manifold Pressure, In. W.C.
Natural
4.0
″
L.P.
10.0
″