Pressure Switch Settings - State Water Heaters SUF 119300 Service Handbook

Commercial gas high efficiency water heaters

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Table Of Contents

Table of Contents

Activation Pressures: Pressure Switch Settings Table below shows the activation pressures and tolerance

for each of the three pressure switches. A + sign before the pressure indicates a positive pressure; above

atmospheric pressure. A - sign before the pressure indicates a negative pressure (in a vacuum); below

atmospheric pressure. Tolerances are specified to allow reasonable leeway for imperfections and inherent

variability without compromising performance.

Models

SUF 60120

SUF 100150-100250

SUF 119300-119500

Pressure Test:

1. Turn off the circuit breaker that serves the water heater.

2. Disconnect the sensing tube from the switch being tested and add a 3/16" tee to the sensing tube. Add a

short piece of sensing tube connecting the tee and the pressure switch being tested.

3. Connect a digital manometer to the open side of the tee with another piece of sensing tube.

4. Restore power to the water heater, if the water heater does not begin a heating cycle raise the Operating

Set Point to activate a heating cycle.

5. When the Combustion Blower comes on and ramps up to full speed, record the pressure reading.

6. Repeat this test for all three pressure switches as necessary.

7. Compare the pressure readings taken to the activation pressures in the Table above.

8. Ensure all sensing tubes are properly routed and reconnected when testing is complete. The pressure

switches will not operate properly if there are leaks in the tubing. Reset the Operating Temperature Set

Point if it was adjusted. Run the water heater through a complete heating cycle before leaving to ensure

it is operating properly. Draw water from the nearest faucet to make sure that the water temperature does

not pose a scalding hazard due to the increased temperature set points that were used in this procedure.

Results/Actions

Blocked Air Intake: Note these are negative pressures; in a vacuum. If the pressure reading taken at the

Blocked Air Intake Switch sensing tube does not reach or drop lower than the pressure shown in the above

Table AND the switch contacts were opening during the "Continuity Test During Operation" shown on Page

13 - the switch is defective and must be replaced. If the pressure reading taken reaches or drops lower than

the pressure shown in the "Pressure Switch Settings" on page 15 and the switch contacts were opening

during the "Continuity Test During Operation" on page 14 - the switch IS NOT defective and should not be

replaced. Check for restrictions at the intake air connection on the water heater, check for too small of pipe

installed, too many equivalent feet and/or too many elbows in the intake air piping. Check for low points in the

intake air piping where water may be collecting and blocking the intake air piping. Check for any restrictions

or debris at the intake air termination outdoors. Check for condensate/water in the sensing tube/switch, if the

sensing tube has water in it, replace the Blocked Air Intake Switch and the tube. Ensure the sensing port is

oriented properly, see "Intake Air Connection" on page 33.

Blocked Exhaust: If the pressure reading taken at the Blocked Exhaust switch sensing tube does not reach or rise

above the activation pressure given in the above Table AND the switch contacts were opening during the "Continuity

Test During Operation" on page 14 - the switch is defective and must be replaced. If the pressure reading taken

reaches or exceeds the pressure shown in the "Pressure Switch Settings" on page 15 and the switch contacts

were opening during the "Continuity Test During Operation" on page 14 - the switch IS NOT defective and

should not be replaced. Ensure the condensate drain connected to the exhaust elbow on the water heater is not

clogged and is draining freely. Check for restrictions or blockage in the vent pipe, check for too small of pipe installed,

too many equivalent feet and/or too many elbows in the vent piping. Check for low points in the vent pipe where water

may be collecting and blocking the vent piping. Check for any restrictions or debris at the vent termination outdoors.