Lochinvar 90, 500 Pressure Only Relief Valve, Water Flow Switch if equipped, Thermal Expansion

Installation & Service Manual

7Domestic water heaters (continued)

Relief Valve

RELIEF

VALVE

FLOW

SWITCH

Figure 7-8_Relief Valve - Water heater Figure 7-9_Water Flow Switch, Water heater

This appliance is supplied with a relief valve sized in accordance with ASME Boiler and Pressure Vessel Code, Section IV (“Heating Boilers”). The relief valve is mounted directly into the heat exchanger inside the header (see FIG.’s 7-8 and 7-9). To prevent water damage, the discharge from the relief valve shall be piped to a suitable floor drain for disposal when relief occurs. No reducing couplings or other restrictions shall be installed in the discharge line. The discharge line shall allow complete drainage of the valve and line. Relief valves should be manually operated at least once a year.

Pressure Only Relief Valve

This water heater/hot water supply boiler is normally supplied with a temperature and pressure relief valve sized in accordance with applicable codes. Units may be supplied with an optional pressure only relief valve. When a water heater/hot water supply boiler equipped with this optional relief valve is piped to a separate storage vessel, the storage vessel must have a properly installed temperature and pressure relief valve which complies with local codes.

￿ CAUTION Avoid contact with hot discharge water.

Water Flow Switch (if equipped)

A water flow switch is available as a factory supplied option on all water heaters. The flow switch should be wired between terminals X and B. Remove the jumper between the X and B terminals on the terminal strip. This wiring connection installs the flow switch in the 24 VAC safety circuit to prove water flow before main burner ignition. A flow switch installed with the factory supplied minimum adjustment setting requires a specific minimum flow to make the switch and start burner operation. The flow rate required is a function of the diameter of pipe and tee used for installation. Ensure that the pump installed water heater will supply adequate flow to make the flow switch contacts and operate the water heater.

Thermal Expansion

A relief valve which discharges periodically may be due to thermal expansion in a closed system. A hot water supply boiler installed in a closed system, such as one with a backflow preventer or check valve installed in the cold water supply, shall be provided with means to control expansion. Contact the water supplier or local plumbing inspector on how to correct this situation. Do not plug or cap the relief valve discharge!

Cathodic Protection

Hydrogen gas can be produced in a hot water system that has not been used for a long period of time (generally two weeks or more). Hydrogen gas is extremely flammable. To prevent the possibility of injury under these conditions, we recommend the hot water faucet be open for several minutes at the kitchen sink before you use any electrical appliance which is connected to the hot water system. If hydrogen is present, there will be an unusual sound such as air escaping through the pipe as the hot water begins to flow. There should be no smoking or open flames near the faucet at the time it is open.

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