17
provided on the upstream side of the gas valve. A manifold pressure
tap is provided on the manifold. The normal manifold pressure for
full input is 3.5” w.c. on natural gas and 10.0” w.c. for propane gas.
Minimum gas supply pressure is 5.5” w.c. for natural gas and 11.0”
for propane gas. In order to obtain rating, gas supply pressure must
be 11.0” w.c. for propane gas.
The pressure regulator on LP gas models is adjusted for 10.0” w.c.
manifold pressure and is intended to prevent over-firing only. Do
not attempt adjustment of the built-in pressure regulator unless
the supply pressure is at least 7.0” w.c. on natural gas or 14.0” w.c.
on propane gas. Check the location of the ignition electrode and
the flame sensor for correct gap setting.
Flame
Sensor
Ignitor
NATURAL
PROPANE (LP)
350,000
7
50,000
#30
#48
400,000
8
50,000
#30
#48
GAS ORIFICES
MAXIMUM
INPUT
(BTUH)
NUMBER
of
BURNERS
MAXIMUM
BTUH/BURNER
HEAT EXCHANGER AND BURNER ORIFICE SPECIFICATIONS
NOTE:
Gas appliances located more than 2000 feet above sea
level must be derated 4% per 1000 feet of total elevation and that
variance in gas heating value and specific gravity require change in
manifold pressure to obtain rating, it is mandatory that the input
be adjusted at the installation site. All installations should be made
as outlined in the latest edition of the National Fuel Gas Code ANSI
Z223.1, section “Procedures To Be Followed To Place An Appliance in
Operation”. Refer also to the “User’s Information Manual” supplied
with the unit for additional information on the gas furnace.
Gas Supply And Manifold Check
Gas supply pressure and manifold pressure with the burners oper-
ating must be as specified on the rating plate.
Gas Inlet Pressure Check
Gas inlet pressure must be checked and adjusted in accordance to
the type of fuel being consumed.
With Power And Gas Off:
1. Connect a water manometer or adequate gauge to the
inlet pressure tap of the gas valve.
Inlet gas pressure can also be measured by removing the
cap from the dripleg and installing a predrilled cap with a
hose fitting.
With Power And Gas On:
2. Put unit into heating cycle and turn on all other gas
consuming appliances.
NATURAL
Min. 5.0" W.C., Max. 10.0" W.C.
PROPANE
Min. 11.0" W.C., Max. 14.0" W.C.
INLET GAS PRESSURE
NOTE:
Inlet Gas Pressure Must Not Exceed the Maximum Value
Shown.
If operating pressures differ from above, make necessary pressure
regulator adjustments, check piping size, etc., and/or consult with
local utility.
Manifold Pressure Check
The gas valve has a tapped opening to facilitate measurement
of the manifold pressure. A “U” Tube manometer having a scale
range from 0 to 12 inches of water should be used for this mea-
surement. The manifold pressure must be measured with the
burners operating.
To adjust the pressure regulator, remove the adjustment screw or
cover on the gas valve. Turn out (counterclockwise) to decrease
pressure, turn in (clockwise) to increase pressure. Only small
variations in gas flow should be made by means of the pressure
regulator adjustment. In no case should the final manifold pressure
vary more than plus or minus 0.3 inches water column from the
specified nominal pressure. Any major changes in flow should be
made by changing the size of the burner orifices. The measured
input rate to the furnace must not exceed the rating specified on
the unit rating plate.
For natural gas, the manifold pressure must be between 3.2 and
3.8 inches w.c. (3.5 nom inal) for high fire and between 1.7 and 2.3
inches w.c. (2.0 nominal) for low fire.
For propane gas, the manifold pressure must be between 9.7 and
10.3 inches w.c. (10.0 nominal) for high fire and between 6.7 and
7.3 inches w.c. (7.0 nominal) for low fire.
Gas Input (Natural Gas Only) Check
It is the responsibility of the contractor to adjust the gas input to
the unit.
To measure the gas input use a gas meter and proceed as
follows:
1. Turn off gas supply to all other appliances except the unit.
2. With the unit operating, time the smallest dial on the meter
for one complete revolution. If this is a 2 cubic foot dial,
divide the seconds by 2; if it is a 1 cubic foot dial, use the
seconds as is. This gives the seconds per cubic foot of gas
being delivered to the unit.
