ULTRAFORCE COMMERCIAL GAS WATER HEATER
SUF 120 thru 400 SERVICE HANDBOOK
CONTROLS – PRESSURE SWITCHES – ALL MODELS
All SUF models are provided with four pressure switches. T hese s witches ar e es sential to the safe an d pr oper op eration o f the uni t. T he switches are wired to the central control board (CCB) individually an d ea ch i s monitored individually. The (CCB) is set up to shut the unit down whenever there is a failure of any of the switches and declare a fault for each individual switch. It is important to understand the purpose of each switch.
Low Gas Pressure |
Sw itch |
Pressure |
Sw itches |
BLOCKED OUTLET PROVING SWITCH
The blocked outlet proving switch electrical contacts are normally closed. The blocked outlet proving switch el ectrical c ontacts w ill open on a rise in pressure. Check t o see i f t he c ondensate i s allowed to flow freely from the exhaust elbow and for obstructions in the exhaust venting and exhaust vent t erminal. Also c heck the t hat t he equivalent feet of vent pipe for the specific model has not been exceeded. Check the vent length tables on page 9
BLOCKED INLET PROVING SWITCH
The Blocked Inlet Proving switch electrical contacts are normally closed. The bl ocked i nlet pr oving switch el ectrical c ontacts w ill op en when an
increase in negative pressure (vacuum) occurs in the intake vent pipe. The switch is connected to the pressure tap on the PVC flange connected to the inlet of the blower. When this switch prevents the u nit f rom ig niting, most li kely the in take is blocked by some means. Verify that the air intake pipe and ai r i ntake v ent t erminal ar e f ree of obstructions that may prevent air from entering the unit. Also check the that the equivalent feet of vent pipe for the specific model has not been exceeded. Check the vent length tables on page 9
BLOWER PROVING SWITCH
The Blower Proving S witch i s pr ovided on t he heater t o v erify that t he f an i s op erating. It i s a positive pressure switch whose electrical contacts are normally open. Th e blower p roving switch electrical contacts will close on a rise in pressure as the blower increases the pressure in the burner. This switch i s c onnected t o t he b urner t ap b y a piece of Tygon (s oft pl astic) t ubing. This t ubing must be connected in order for the switch to close the electrical contacts. The controller requires that the electrical contacts on this p ressure switch b e open before it will allow the blower to come on. The control w ill declare a f ault on the U IM if ei ther condition occurs.
LOW GAS PRESSURE SWITCH
The Low Gas Pressure Switch electrical contacts are normally open. The low gas pressure switch electrical contacts will close on a rise pressure. The c ontacts w ill open w hen t he p ressure falls below the fixed set point. If this happens during a heating cycle a the burner will be shut down and a fault will be declared on the UIM.
State Water Heaters – Technical Training Department 27 | Ashland City, Tennessee © 2009 |
Servicing should only be performed by a Qualified Service Agent |
