1101790-UIM-C-0414
30
Johnson Controls Unitary Products
Figure 12: Two Stage Gas Valve Front
Figure 13: Two Stage Gas Valve Rear
Adjust as follows:
1.
Remove the cap from the valve body. See Figures 14 and
12 for location.
2.
To decrease the gas pressure, turn the adjusting screw
counterclockwise.
3.
To increase the gas pressure, turn the adjusting screw
clockwise.
NOTE:
The correct manifold pressure for natural gas furnaces
is 3.5 IWG high heat and 1.5 IWG low heat. The correct
manifold pressure for propane (LP) is 10.0 IWG high
heat and 4.5 IWG low heat.
Burner Instructions
To check or change the burners, CLOSE THE MAIN MANUAL
SHUT-OFF VALVE AND SHUT OFF ALL POWER TO THE
UNIT.
1.
Remove the two (2) #8 screws holding each burner in place.
2.
Remove the burner assembly from the manifold assembly
by moving the burner assembly forward, turn at an angle
and pull back.
3.
Burners are now accessible for service.
Pilot Instruction
To adjust the pilot flame:
Figure 14: Proper Flame Adjustment
1.
Remove the pilot adjustment cover screw.
2.
Adjust the pilot adjustment screw to achieve the proper
pilot flame.
3.
The pilot flame should envelope 3/8” of the end of the flame
sensor and not contain any yellow color, see Figure 14.
4.
Replace the pilot adjustment cover screw after the pilot
flame is set.
To check, adjust or remove the hot surface pilot assembly,
CLOSE THE MAIN MANUAL SHUT-OFF VALVE AND SHUT
OFF ALL POWER TO THE UNIT.
1.
Disconnect the wiring from the control board to the pilot
assembly.
2.
Remove the two (2) #8 screws holding the pilot assembly
in place.
3.
Remove the pilot assembly.
Adjustment of Temperature Rise
After about 20 minutes of high heat operation, determine the
furnace temperature rise. Take readings of both the return air
and the heated air in the ducts about six feet from the furnace
where they will not be affected by radiant heat.
The temperature rise (or temperature difference between the
return air and the heated air from the furnace) must lie within
the range shown on the rating plate and the data in Tables 11
thru 11.
After the temperature rise has been determined, the CFM can
be calculated as follows:
Hi Fire
(2nd Stage)
Manifold Pressure
Low Fire
(1st Stage)
Manifold Pressure
Adjustment
Electrical
Connection
½
NPT
(Outlet)
Manifold
Pressure
Tap
Pilot
Gas
Connect
Pilot
Adjustment
(Remove Cap)
Manual
Gas
Switch
Line Pressure
Tap
½
NPT
(Inlet)
8
3
"
Pilot
Spark Ignitor
Flame Sensor
min.