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High-Efficiency Commercial Gas Series - Service Manual
GAS PRESSURES – 120 and 150 KBtu/hr MODELS
ADJUSTMENT PROCEDURE:
GAS PRESSURE
120 AND 150 MODELS
Verify supply gas pressure is within the
requirements given in the Instruction Manual
that came with the water heater and shown in
the table on page 4 prior to start up.
A supply gas pressure regulator
(service regulator) must be installed on
the gas supply line within 10' (305 cm)
of the unit.
1
.Check gas line pressure with a manometer.
2.Check manifold pressure with a manometer
connected to the manifold pressure tap on the gas
control valve,
If full rate adjustment is required, remove cover screw
from top of the gas control valve. Using a small
screwdriver, turn adjusting screw clockwise to
increase or counterclockwise to decrease gas
pressure to obtain manifold pressures given in the
table on page 4.
3. Cycle the burner on and off several times to check
and check operation.
HIGH ALTITUDE INSTALLATIONS
120 AND 150 MODELS
For appliance installation locations with elevations
above 6,500 feet (1982 meters) consult the "High
Altitude Installation" section of the Instruction Manual
that came with the water heater.
Technical Literature Department
Servicing should only be performed by a Qualified Service Agent
CHECKING THE FIRING RATE
a. Attach a manometer to the manifold pressure tap
on the gas valve – refer to the table on page 4 for
correct pressure.
b. Use this formula to "clock" the meter. Be sure
other gas consuming appliances are not operating
during this interval.
Btuh = 3600 X H/ T
T = Time in seconds to burn 1 cubic foot of gas.
(With a stopwatch read the gas meter and measure
the amount of time required for the heater to consume
1 cubic foot of gas.)
H = Heating value of gas (in Btu's per cubic foot of
gas).
Btuh = Actual heater input rate, in Btuh.
EXAMPLE: (150 KBtu/hr model)
T = 25.25 seconds
H = 1050 Btu/ft.3
BTUH = ?
Compare result to the de-rated input required for
the elevation at the installation location.
Should it be necessary to adjust the gas pressure to
the burner, to obtain the full input rate, the steps below
should be followed:
c. Remove the pressure regulator cover screw and
adjust the pressure by turning the adjusting screw with
a small screwdriver. Do not exceed 4.0" (1 kPa)
natural gas models and 10.0" w.c. (2.5kPa) on the
propane models. Clockwise to increase gas pressure
and input rate. Counterclockwise to decrease gas
pressure and input rate.
d. "Clock" the meter as in step (b) above.
e. Repeat steps (c) and (d) until the specified input
rate is achieved.
f. Turn the manual gas valve to "OFF". Replace the
pressure regulator cover screw. Remove the pressure
gauge or manometer from the manifold pressure tap.
Replace the set screw in the manifold pressure tap. If
the gas pressure regulator cannot be adjusted to give
the full input rating with sufficient gas pressure at the
valve, check to ensure the unit is equipped with the
correct orifice.
5
Ashland City, Tennessee © 2008
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