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CAUTION
Be sure to relight any gas appliances
that were turned off at the
start of this input check.
TABLE 10: Inlet Gas Pressure Range
INLET GAS PRESSURE
RANGE
l
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" (3.24 kPa) W.C.
IMPORTANT:
The inlet gas pressure
operating
range table specifies
the minimum and maximum
gas line pressures
required for safe fur-
nace operation.
The minimum inlet gas pressure required to obtain the BTU input speci-
fied on the rating plate and in these instructions
is shown below:
4.5" W.C. (1.12 kPA) for Natural Gas
11.0" W.C. (2.74 kPA)for
Propane (LP) Gas
ADJUSTMENT
OF MANIFOLD
GAS
PRESSURE
Manifold gas pressure may be measured at 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 R
2.
The gas line pressure must be taken at the port marked IN R
3.
Using a 3/32" Allen wrench,
loosen the setscrew
by turning it 1
turn counter clockwise.
DO NOT REMOVE
THE SET SCREW
FROM THE PRESSURE
PORT.
4.
Use the 4" (10.2 cm) piece of 1/8" (0.3 cm) tubing to connect the
positive side of the manometer
to the gas valve pressure
refer-
ence port. Refer to Figure 23 for connection details.
IMPORTANT:
The cap for the pressure
regulator
must be removed
entirely to gain access to the adjustment screw. Loosening or tightening
the cap does not adjust the flow of gas.
5.
Refer to Figure 22 for location of pressure
regulator
adjustment
cap and adjustment
screw on main gas valve.
6.
Turn gas and electrical
supplies
on and follow the operating
instructions to place the unit back in operation.
7.
Adjust manifold
pressure by adjusting gas valve regulator
screw
for the appropriate gas per the following:
TABLE 11: Nominal Manifold Pressure
NOMINAL
MANIFOLD
PRESSURE
Natural Gas
3.5" w.c. (0.87 kPa)
Propane (LP) Gas
10.0" w.c. (2.488 kPa)
OUTLET ........
PRESSURE
_
_
I"_
PORTiNLET_..__
U7
WRENCH J _---_'_J,_c;u:::_-"
Boss
__
<
INLET/
PRESSURE
PORT
VENT PORT
J
-°uTLET
IN REGULATOR
O
ADJUSTMENT
ON/OFF SWITCH
(Shown in OFF position)
FIGURE 22: Gas Valve
98618/035-20009-001
Rev. B (1205)
IMPORTANT:
If gas valve regulator
is turned in (clockwise),
manifold
pressure is increased.
If screw is turned out (counterclockwise),
mani-
fold pressure will decrease.
8.
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 (NATURAL GAS)".
9.
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 and tighten the pressure tap plug using the 3/32" Allen wrench.
10.
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.
AWARNING
The manifold pressure must be checked with the screw-off cap for
the gas valve pressure regulator in place. If not, the manifold pres-
sure setting could result in an over-fire condition. A high manifold
pressure
will cause an over-fire condition, which could cause pre-
mature heat exchanger failure. If the manifold pressure is too low,
sooting and eventual
clogging of the heat exchanger could occur.
Be sure that gas valve regulator
cap is in place and burner box to
gas valve pressure reference hose is connected.
MAINFOLD PRESSURE
"U" TUBE CONNECTION
r"Q] _
OUTLET
_l_l_mql_
/
PRESSURE TAP
GAS VALVE-"- "_[_
_
MANIFOLD PIPE
I
__
k,---.'_
I
_
i"_
_ _
z-_.
/
1/4" TUBING
.....
\
II t-._-IIlL 3.51N
i _t-_4q44_WATER
FLAME
U-TUBE
IIN-+-tII
COLUMN
SENSOR
MANOMETER
III__-_t_ GAS
II-___-lUl I PRESSURE
' SHOWN
FIGURE 23: Reading Gas Pressure
ADJUSTMENT
OF TEMPERATURE
RISE
ADANGER
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 8 "ELECTRICAL
AND PERFORMANCE
DATA ".
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.
Unitary Products Group
19
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