A.O. Smith FMD 40, FMD 50, FMD 30, 315795-000 MH Filling the Water Heater, GAS Piping

FILLING THE WATER HEATER

Never use this water heater unless it is completely full of water. To prevent damage to the tank, the tank must be filled with water. Water must flow from the hot water faucet before turning “ON” gas to the water heater.

To fill the water heater with water:

1.Close the water heater drain valve by turning the handle to the right (clockwise). The drain valve is on the lower front of the water heater.

2.Open the cold water supply valve to the water heater.

NOTE: The cold water supply valve must be left open when the water heater is in use.

3.To insure complete filling of the tank, allow air to exit by opening the nearest hot water faucet. Allow water to run until a constant flow is obtained. This will let air out of the water heater and the piping.

4.Check all water piping and connections for leaks. Repair as needed.

GAS PIPING

Make sure the gas supplied is the same type listed on the model rating plate. The inlet gas pressure must not exceed 10.5” W.C. for natural gas and 13” W.C. for propane (L.P.) gas. The minimum inlet gas pressure shown on the rating plate is that which will permit firing at rated input.

If the gas control valve/thermostat is subjected to pressures exceeding 1/2 pound per square inch (3.5 kPa), the damage could result in a fire or explosion from leaking gas.

If the main gas line Shut-off serving all gas appliances is used, also turn “off” the gas at each appliance. Leave all gas appliances shut “off” until the water heater installation is complete.

A gas line of sufficient size must be run to the water heater. Consult the current edition of Natural Gas and Propane Installation Code (CAN/CSA B149.1) and your gas supplier concerning pipe size.

There must be:

•A readily accessible manual shut off valve in the gas supply line serving the water heater, and

•A drip leg (sediment trap) ahead of the gas control valve/ thermostat to help prevent dirt and foreign materials from entering the gas valve.

•A flexible gas connector or a ground joint union between the shut off valve and control valve to permit servicing of the unit.

Be sure to check all the gas piping for leaks before lighting the water heater. Use a soapy water solution, not a match or open flame. Rinse off soapy solution and wipe dry.

When installed at elevations above 4,500 feet (1371 m), input rating should be reduced at the rate of 4 percent for each additional 1,000 feet (305 m). This requires replacement of the burner orifice in accordance with the Natural Gas and Propane Installation Code (CAN/CSA B149.1-current edition). Contact your local gas supplier for further information.

Failure to replace the standard orifice with a high altitude orifice when installed could result in improper and inefficient operation of the appliance, producing carbon monoxide gas in excess of safe limits, which could result in serious injury or death. Contact your gas supplier for any specific changes which may be required in your area.

Use pipe joint compound or teflon tape marked as being resistant to the action of petroleum [Propane (L.P.)] gases.

The appliance and its gas connection must be leak tested before placing the appliance in operation.

The appliance and its individual Shut-off valve shall be disconnected from the gas supply piping system during any pressure testing of that system at test pressures in excess of 1/2 pound per square inch (3.5 kPa). It shall be isolated from the gas supply piping system by closing its individual manual Shut-off valve during any pressure testing of the gas supply piping system at test pressures equal to or less than 1/2 pound per square inch (3.5 kPa).

Connecting the gas piping to the gas control valve/thermostat of the water heater can be accomplished by either of the two methods shown in Figures 27, 28 and 29.

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