Installation manual

1083292-UIM-A-0114
Johnson Controls Unitary Products 37
ADJUSTMENT OF MANIFOLD GAS PRESSURE
Inlet and manifold gas pressure may be measured by connecting the
“U” tube manometer to the gas valve with a piece of tubing. Follow the
appropriate section in the instructions below. Refer to Figure 45 for the
locations of the pressure ports on the gas valve.
Turn gas off at the ball valve or gas cock on gas supply line
before the gas valve. Find the pressure ports on the gas
valve marked Out P and In P.
1. The manifold pressure must be taken at the port marked OUT P.
2. The inlet gas line pressure must be taken at the port marked IN P.
3. Using a 3/16” allen wrench, remove the plugs from the inlet and
outlet pressure ports. Connect a 1/8” UPT barbed hose fitting to
each pressure port.
4. Refer to Figure 45 for location of pressure regulator adjustment
screw on main gas valve.
5. Turn gas and electrical supplies on and follow the operating
instructions to place the unit back in operation.
6. Use a small slotted screwdriver to turn the regulator adjustment
screw. Adjust the pressure by turning the screw one click at a time
until desired pressure is reached. Wait a few seconds after each
adjustment to allow the pressure to stabilize before making addi-
tional adjustments. This is an electronic adjustment screw that
does not require very much force. Application of excessive force to
the adjustment screw will damage the gas valve.
7. After the manifold pressure has been adjusted, re-calculate the
furnace input to make sure you have not exceeded the specified
input on the rating plate. Refer to "CALCULATING THE FURNACE
INPUT (NAT. GAS)".
8. Once the correct BTU (kW) input has been established, turn the
gas valve to OFF and turn the electrical supply switch to OFF; then
remove the flexible tubing and fittings from the gas valve pressure
tap replace the pressure tap plugs.
9. Turn the electrical and gas supplies back on, and with the burners
in operation, check for gas leakage around the gas valve pressure
port for leakage using an approved gas detector, a non-corrosive
leak detection fluid, or other leak detection methods.
ADJUSTMENT OF TEMPERATURE RISE
After about 5 minutes of operation, determine the furnace temperature
rise. Take temperature readings of both the return air and the heated air
in the ducts about six feet away from the furnace, where they will not be
affected by radiant heat. Increase or decrease the temperature rise by
changing the ATR jumper on the furnace control board. The jumper is
factory-set to deliver an air temperature rise near the midpoint of the
nameplate temperature rise range. If more air is desired (lower temper-
ature rise), move the jumper to the -10 position. If less air is desired
(higher temperature rise), move the jumper to the +10 position.
Table 15: Inlet Gas Pressure Range
INLET GAS PRESSURE RANGE
Natural Gas Propane (LP)
Minimum* 4.5” w.c. (1.12 kPa) 8.0” w.c. (1.99 kPa)
Maximum 10.5” w.c. (2.61 kPa) 13.0” w.c. (3.24 kPa)
The inlet gas pressure operating range table specifies what the
minimum and maximum gas line pressures must be for the furnace
to operate safely. The gas line pressure MUST BE
a minimum of:
• 7” w.c. (1.74 kPA) for Natural Gas
• 11” w.c. (2.74 kPA) for Propane (LP) Gas
in order to obtain the BTU input specified on the rating plate and/or
the nominal manifold pressure specified in these instructions and
on the rating plate.
The regulated outlet pressure has been calibrated at the factory.
Additional pressure adjustment should not be necessary. If adjust-
ment is necessary, set to the following specifications. After adjust-
ment, check for gas leakage.
TABLE 16:
Nominal Manifold Pressure
NOMINAL MANIFOLD PRESSURE
Natural Gas (Max) 3.5" w.c. (0.87 kPa)
Natural Gas (Min) 0.5" w.c. (0.15 kPa)
Propane (LP) Gas (Max) 10.0" w.c. (2.49 kPa)
Propane (LP) Gas (Min) 1.6" w.c. (0.40 kPa)
NOTICE
FIGURE 45: Gas Valve
If gas valve regulator is turned clockwise, manifold pressure is
increased. If screw is turned counterclockwise, manifold pressure
will decrease.
The adjustment screw has a range of 16 clicks (about ±0.5” mani-
fold pressure). There is not a hard stop at the ends of the adjust-
ment range. When the limit of the adjustment range is reached, the
next click will start over at the other end of the range. For instance,
if you are increasing pressure and reach the upper limit of adjust-
ment the next click will drop the pressure to the lower limit.
The temperature rise, or temperature difference between the return
air and the supply (heated) air from the furnace, must be within the
range shown on the furnace rating plate and within the application
limitations shown in Table 6.
The supply air temperature cannot exceed the “Maximum Supply
Air Temperature” specified in these instructions and on the fur-
nace rating plate. Under NO circumstances can the furnace be
allowed to operate above the Maximum Supply Air Temperature.
Operating the furnace above the Maximum Supply Air Temperature
will cause premature heat exchanger failure, high levels of Carbon
Monoxide, a fire hazard, personal injury, property damage, and/or
death.
Inlet
Pressure
Tap
Outlet
Pressure
Tap
On/Off
Switch
Main
Regulator
Adjustment