Hubbell STH manual Adjustment Of Pilot Operated Valves

f.Apply air pressure to valve diaphragm so that stem halves are aligned and re-connect stem halves.

g.If valve will not open with air on the diaphragm, spring tension should be decreased.

h.Adjustment is essentially the same as if spring tension were increased except the adjustment screw is turned in the opposite direction.

5.ADJUSTMENT OF PILOT OPERATED VALVES

a.Pilot operated valves such as Spence or Spirax/Sarco are not fail safe. These valves have a liquid or gas filled thermo-static bulb and if this bulb loses its charge, the valve will go to its full open position and cause overheating of the water heater. This situation should be considered before attempting to adjust these valves.

b.Spirax/Sarco Valves are completely pre-set at the factory and there is no spring adjustment. Set the thermostat at the desired temperature and no further adjustment is required.

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