5715184-BIM-A-0519
Johnson Controls Ducted Systems
27
VERIFY MANIFOLD GAS PRESSURE AND INPUT
RATE
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 31 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 gas line pressure must be taken at the port marked IN P.
3.
Using a 3/32 in. (2.4 mm) hex head wrench, loosen the set screw
by turning it 1 turn counter clockwise. DO NOT REMOVE THE SET
SCREW FROM THE PRESSURE PORT.
Read the inlet gas pressure
Connect the positive side of the manometer to the IN P Tap on the gas
valve. Do not connect any tubing to the negative side of the manometer,
as it references atmospheric pressure. Refer to Figure 31 for connec-
tion details.
1.
Turn gas and electrical supplies on and follow the operating instruc-
tions to place the unit back in operation.
2.
Once the correct gas inlet pressure has been established (see
Table 15), turn the gas valve to OFF and turn the electrical supply
switch to OFF. Remove the flexible tubing from the gas valve pres-
sure tap and tighten the pressure tap plug using the 3/32 in. (2.4
mm) hex head wrench.
3.
Turn the electrical and gas supplies back on, and with the burners
in operation, check for gas leakage around the gas valve pressure
port using an approved non-corrosive gas leak detection fluid, or
other non-flammable leak detection methods.
Read the manifold gas pressure
Connect the positive side of the manometer to the OUT P Tap on the
gas valve. Do not connect any tubing to the negative side of the
manometer, as it references atmospheric pressure. Refer to Figures 31
and 32 for connection details.
Table 15:
Inlet Gas Pressure Range
INLET GAS PRESSURE RANGE
Natural Gas
Propane (LP)
Minimum
4.5 in. W.C. (1.12 kPa)
8.0 in. W.C. (1.99 kPa)
Maximum
10.5 in. W.C. (2.61 kPa) 13.0 in. W.C. (3.24 kPa)
IMPORTANT:
The inlet gas pressure operating range table speci-
fies what the minimum and maximum gas line pressures must be
for the furnace to operate correctly. The gas line pressure
MUST
BE
a minimum of:
•
7 in. W.C. (1.74 kPa) for Natural Gas
•
11 in. W.C. (2.74 kPa) for Propane (LP) Gas
This is 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.
NOTICE
The regulated outlet pressure has been calibrated at the factory.
Table 16:
Nominal Manifold Pressure
NOMINAL MANIFOLD PRESSURE
Natural Gas
3.5 in. W.C. (0.87 kPa)
Propane (LP) Gas
10.0 in. W.C. (2.488 kPa)
FIGURE 31:
Gas Valve
MANIFOLD PRESSURE U TUBE CONNECTION
FIGURE 32:
Reading Gas Pressure
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