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Servicing should only be performed by a Qualied Service Agent
INSTALLATION QUICK TIPS – SUF 120 AND 150 GAS PRESSURE
ADJUSTMENT PROCEDURE: GAS PRESSURE SUF 120 AND 150 MODELS
Main line gas pressure to the water heater for natural gas should be between a maximum of 10.5" w.c.
(2.59 kPa) for natural gas, 14.0" w.c. (3.45 kPa) for propane and a minimum of 4.8 w.c. (1.18 kPa) for
Natural Gas, and 8.5" w.c. (2.08 kPa) for Propane Gas. Also see gas pressure specification table on
page 4.
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 gauge (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 4.0" w.c. (1 kPa) for natural gas and 10.0" w.c. (2.5 kPa) for L.P.
Gas.
3. Cycle the burner on and off several times to check its operation.
4. Check the operation of the limit and operating controls.
5. Check the vent system seams and joints and ensure that there is no discharge of flue products into
the room.
6. Check the input rate.
HIGH ALTITUDE INSTALLATIONS SUF 120 ‑ 150
For appliance installation locations with elevations above 6,500 feet (1982 meters) consult the “High
Altitude Installation” section of the owners manual.
1. Attach a pressure gauge (manometer) to the manifold pressure tap and refer to page 4 for correct
pressure.
2. 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: (Using SUF-150 heater)
T = 25.25 seconds
H = 1050 Btu/ft.
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BTUH = ?