Installation Quick Tips - Suf 120 And 150: Gas Pressure - State Water Heaters SUF60 Service Handbook

INSTALLATION QUICK TIPS – SUF 120 AND 150: GAS PRESSURE
ADJUSTMENT PROCEDURE: MANIFOLD 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. (2.62
kPa) for natural gas, 14.0" w.c. (3.49 kPa) for propane and a minimum of 4.8 w.c. (1.20 kPa) for Natural
Gas, and 8.5" w.c. (2.12 kPa) for Propane Gas. Also see "Gas Pressure Specifications" table on Page 4.
A supply gas pressure regulator (service regulator) must be installed on the gas supply line no closer
than 3 equivalent feet (1 meter) and no farther than 8 equivalent feet (2.4 meters) from the water
heater's inlet gas connection if the gas pressure is above maximum pressure or not stable.
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 manifold pressure adjustment is required, remove cover screw from top of the gas
control valve. Using a small screwdriver, turn adjusting screw clockwise to increase gas pressure or
counterclockwise to decrease gas pressure to obtain 4.0" w.c. (1.0 kPa) for natural gas and 10.0" w.c.
(2.49 kPa) for Propane (LP) Gas.
3. Cycle the burner on and off several times to check for proper operation.
4. Check the high limit and operating controls for proper operation.
5. Check the vent system seams and joints and ensure that there is no leakage of flue products into the
room.
6. Verify correct input rate (see below).
HIGH ALTITUDE INSTALLATIONS SUF 120 ‑ 150
For water heater 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.
BTUH = ?
Compare result to the de‑rated input required for the elevation at the installation location.
If it is necessary to adjust the gas pressure to the burner in order to obtain the full input rate, the steps
below should be followed:
1. Remove the pressure regulator cover screw and adjust the pressure by turning the adjusting screw
with a small screwdriver. Turn adjusting screw clockwise to increase gas pressure and input rate
and counterclockwise to decrease gas pressure and input rate. Do not exceed 4.0" (1.0 kPa) for
natural gas models and 10.0" w.c. (2.49 kPa) for propane models.
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Servicing should only be performed by a Qualified Service Technician