506271-01
Page 9 of 14
Issue 0921
Manifold Gas Pressure Adjustment Regulator – Natural
Gas
For purpose of input adjustment, the minimum
permissible gas supply pressure is 5" w.c. for natural gas.
Gas input must never exceed the input capacity shown on
the rating plate.
The furnace is equipped for natural gas
rated inputs with manifold pressure of 3.5" w.c.
The manifold pressure can be measured by shutting off the
gas, removing the pipe plug in the downstream side of the
gas valve, and connecting a water manometer or gauge.
Under no circumstances should the final manifold
pressure vary more than 0.3" w.c. from the above
specified pressures.
To adjust the regulator, turn the
adjusting screw on the regulator clockwise to increase
pressure and input or counterclockwise to decrease pressure
and input. See Figure 8 to assist in locating the regulator on
the gas valve.
Check the furnace rate by observing the gas meter, making
sure all other gas appliances are turned off. The test hand on
the meter should be timed for at least one revolution, noting
the number of seconds per revolution.
The heating value of
the gas can be obtained from the local utility.
x
3600
x
=
Cubic Feet Per Revolution
BTU/HR
INPUT
# Seconds Per Revolution
Heating
Value
the hand on the 1-cubic foot dial to make a revolution with a
100,000 BTU/HR furnace running. The result is 99,750 BTU/
HR, which is close to the 100,000 BTU/HR rating of the
furnace.
Manifold Gas Pressure Adjustment Regulator –
LPG/Propane Gas
LPG/propane units require a regulator, and a regulator on
the LPG/propane tank is also required.
For purpose of input adjustment, the minimum
permissible gas supply pressure (inlet side of gas valve)
is 11" w.c. for LPG/propane.
If at any time ignition is slow and burner does not seem to
be operating correctly, check manifold pressure (outlet side
of the gas valve).
It should be 10" to 10.5" w.c. pressure
for LPG/propane.
The furnace is designed to obtain rated input at 10" w.c.
manifold pressure for propane.
Example:
By actual measurement, it takes 38 seconds for
To check this pressure:
1.
Turn off gas valve.
2.
Remove plug on valve marked “OUTLET PRESSURE.”
3.
Install a water manometer.
4.
Turn on gas valve and initiate a call for heat. If manifold
pressure must be adjusted, remove cap from pressure
regulator and turn adjustment screw clockwise to
increase pressure or counterclockwise to reduce
pressure.
5.
After checking pressure, turn gas off, remove
manometer fitting, and replace pipe plug and regulator
cap.
6.
Put furnace in operation and check plug for leaks using
soapy solution.
Burner and Burner Orifice Instructions
To check or change burners or burner orifices:
1.
Close the main manual gas shutoff valve and turn
off all power to unit.
2.
Remove the burner access panel.
3.
Disconnect the union in the gas supply line upstream of
the gas valve and downstream of the manual shutoff
valve.
4.
Label wires going to the gas valve, then disconnect the
wires.
5.
To change orifice:
a.
Remove 4 screws that fasten the manifold to the
burner box assembly and remove the manifold.
b.
Remove the orifices, then install replacement
orifices.
c.
To reassemble: Reverse above steps, making sure
orifices are inserted into the orifice holders on the back
end of the burners, and that burners are level and
centered on each burner opening in the vest panel.
6.
To remove or service burners:
a.
Label and disconnect the wires to the rollout switch
and disconnect the igniter and flame sensor leads at
the ignition control.
b.
Remove the 4 screws that secure the burner box
assembly to the vest panel and remove the assembly
from the unit.
c.
Remove the 6 screws that fasten the burner rack
and bottom shield assembly to the burner box. Burners
are now accessible for removal.
d.
To Reassemble: Reverse above steps.
