5168276-XIM-B-0216
44
Johnson Controls Unitary Products
Manifold Gas Pressure Adjustment
Small adjustments to the high-fire gas flow may be made by
turning the pressure regulator adjusting screw on the automatic
gas valve.
Adjust as follows:
1.
Remove the cap on the regulator. It's located next to the
push-on electrical terminals.
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 these furnaces is
3.65 IWG ± 0.3.
Adjustment Of Temperature Rise
The temperature rise (the difference of temperature between the
return air and the heated air from the furnace) must lie within the
range shown on the CSA rating plate and the data in Table 11.
After the temperature rise has been determined, the CFM can
be calculated as follows:
After about 20 minutes of operation, determine the furnace
temperature rise. Take readings of both the return air and the
heated air in the ducts (about 6 feet from the furnace) where
they will not be affected by radiant heat. Increase the blower
CFM to decrease the temperature rise; decrease the blower
CFM to increase the rise (See SUPPLY AIR DRIVE
ADJUSTMENT).
NOTE:
Each gas heat exchanger size has a minimum
allowable CFM. Below this CFM, the limit will open.
Figure 28: Proper Pilot Flame Adjustment
Pilot Checkout
The pilot flame should envelope the end of the flame sensor. To
adjust pilot flame, (1) remove pilot adjustment cover screw, (2)
increase or decrease the clearance for air to the desired level,
(3) be sure to replace cover screw after adjustment to prevent
possible gas leakage.
Put the system into operation and observe through complete
cycle to be sure all controls function properly.
Burner Instruction
To check or change burners, pilot or orifices, CLOSE MAIN
MANUAL SHUT-OFF VALVE AND SHUT OFF ALL ELECTRIC
POWER TO THE UNIT.
1.
Remove the screws holding either end of the manifold to
the burner supports.
2.
Open the union fitting in the gas supply line just upstream
of the unit gas valve and downstream from the main
manual shut-off valve.
3.
Remove the gas piping closure panel.
4.
Disconnect wiring to the gas valves and spark ignitors.
Remove the manifold-burner gas valve assembly by lifting
up and pulling back.
Figure 29: Typical Flame
Burners are now accessible for service.
Reverse the above procedure to replace the assemblies. Make
sure that burners are level and seat at the rear of the heat
exchanger.
Burner Air Shutter Adjustment
Adjust burner shutters so no yellow flame is observed in the
heat exchanger tubes.
Figure 30: Typical Gas Valve
Burner Assembly Bracket
Flame Sensor Bulb
1/8” Gap Between
Carry-over Tube
and Flame Sensor Bulb
Carry-over Tube
Gas Supply Pipe
Pilot Tube
Burner Flame
(Blue Only)
Heat Tube
Exchanger
Burner
Adjustable Shutter
