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8. Move the gas control lever to ON.
9. Close the furnace door and turn the latch.
10. Turn on all electric power to the appliance.
11. Turn the thermostat to ON and set to the
desired setting.
12. If the appliance will not operate after one
re-try, follow the instructions in the “To
Turn Off Gas To Appliance” Section below
and call your service technician or gas
supplier.
To Turn Off Gas to the Appliance
1. Set the thermostat to OFF or to its lowest
setting.
2. Turn off all electric power to the appliance
if service is to be performed.
3. Turn the latch and open the furnace door.
4. Push in the gas control lever and move to
OFF. DO NOT FORCE.
5. Close the furnace door and turn the latch.
Checking the Input of the Furnace
Refer to the rating plate on the furnace to
determine the firing rate for your application.
Using Table 4, determine the appropriate orifice
size for the firing rate and gas being used in your
application. Check the burner orifice to ensure
that it is the correct size.
The input of this furnace can be checked using
the following procedure, which is based on
using a one cubic foot gas meter:
Firing Rate
Natural Gas
Natural Gas
LP Gas
LP Gas Time
Burner
Input
Orifice
Time Per Rev.*
Orifice
Per Rev.**
Designation
(BTUH)
Number
(sec)
Number
(sec)
Gas Gun-65-DI-S
65,000
24
55
43
138
Gas Gun-75-DI-S
75,000
20
48
40
120
Gas Gun-90-DI-S
90,000
16
40
36
100
* There times are based on natural gas at an average of 1,000 BTU per cubic foot, a burner
manifold pressure of 3.5 in WC, and a meter dial size of 1 cubic foot.
** There times are based on LP gas at an average of 2,500 BTU per cubic foot, a burner
manifold pressure of 3.5 in WC, and a meter dial size of 1 cubic foot.
Table 4. Natural and LP Gas Orifices
1.
Shut off all other gas fired appliances,
except for any pilots.
2.
Start the furnace in heating mode and allow
it to run for at least three minutes.
3.
Measure the amount of time (in seconds)
required for the gas meter to complete one
revolution. Note that one revolution will be
equal to one cubic foot of gas.
4.
Compare the time measured with the
appropriate time listed in Table 4. If the time
varies by more that 5% from the times
shown in the table, then measure the inlet
and gas valve manifold pressures, using
the procedure outlined in the “Measuring
the Inlet Supply and Manifold Pressures”
section.
5.
If both the inlet gas pressure and the
manifold pressure are properly set, then
check the burner orifice to ensure that it is
properly sized. Further gas problems
should be referred to the local gas supplier.
Measuring the Inlet Gas and Manifold
Pressures
For natural gas installations, the inlet gas line
pressure at the gas valve inlet must be between
5 in WC and 7 in WC. For LP gas installations,
the incoming gas line pressure at the gas valve
inlet must be between 11 in WC and 13 in WC.
This pressure can be checked at the port
located on the gas inlet end of the gas valve
using a pressure gauge or U-tube manometer,
which must be installed according to the
manufacturer’s supplied instructions.
For natural gas installations, the manifold
pressure must be set at 3.5 in WC. For LP gas
installations, the manifold pressure must be set
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