Bradford-White Corp B4 Pressure Buildup in Water System, Pressure Relief Valve, Water Pressure

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Page 14 BRADFORD WHITE

2.6.6Pressure Buildup in Water System

The water utility supply meter may contain a

check valve, back flow preventer, or water pressure reducing valve that will create a closed water supply system. Contact the water supplier or local plumbing inspector on how to control this situation.

During the heating cycle of the heater, the water expands creating a pressure buildup in the water system. The pressure relief valve may discharge hot water under these conditions, causing a loss/waste of energy and a buildup of lime on the relief valve seat.

NOTE: Do not plug the relief valve.

There are two methods to prevent the relief valve from discharging hot water in a closed water system:

1.Install a pressure relief valve on the cold water supply line. Make sure that the discharge of this valve is directed to an open drain and protected from freezing.

2.Install a properly sized thermal expansion tank on the cold water supply line.

2.6.7 Pressure Relief Valve

The pressure relief valve must be installed in the tapped opening provided in the boiler header with its outlet piped to a drain or floor sink. Special attention must be given to relief valve settings in installations where the boiler is located on the ground floor of a tall building, or where the operating temperature of the boiler is above 210°F. In both instances, the static pressure of the system is elevated, and could cause the relief valve to leak. Where no special setting of the relief valve is ordered, the factory will furnish a 125 psi setting.

WARNING

Hot water can scald! Hot water can produce third degree burns in 6 seconds at 140°F (60°C) and in 30 seconds at 130°F (54°C).

2.6.8 Water Pressure

Keep the water pressure in the system above 30 psi (207 kPa). If the system pressure drops below 30 psi (207 kPa), it could damage the heater through lack of circulation. If for any reason, the water is turned off temporarily, to service the equipment for example, airlock could be a problem when the heater is turned back on. To eliminate the airlock, open the pressure relief valve (see Figure 23) and allow the air to bleed out until water starts to flow. As soon as full circulation is restored, the trapped air will be released through the hot water faucets.

Flow	Pressure
Switch	Relief Valve

High-Limit

Dry Well

Figure 23. Pressure relief valve.

2.6.9 Storage Tank Installation

1.Be sure the floor is structurally capable of supporting the tank when it is filled with water, and is waterproof.

2.Place the tank so that manholes, inspection covers, nameplates and drain valves are accessible.

3.Be sure the tank is suitable for the water in the system. Some water is corrosive and requires a protected tank. Most tanks are available with glass, plastic, or galvanized linings.

4.If the tank is glass-lined, it should be equipped with a suitable magnesium anode. It is a good practice to replace the anode when it is approximately 50 percent used. The factory warranty on a glass-lined tank may be void if a satisfactory anode is not in place at the time of a failure or if it is consumed by cathodic action.

5.The tank must be lined if a water softener is installed in the system.

6.Make sure the tank connections in the heater- tank circulating loop are the proper size (see Section 2.6.5). If tappings are smaller than the recommended pipe size, a larger pump may be required. Consult the factory if in doubt.

7.Install a pipe in the tank drain fitting that goes to a floor sink, and install a drain valve. If a floor sink is not available, install a hose bib.

8.Hot water tanks in an existing installation are likely to have silt deposits on the bottom. Therefore, it is important to extend the pump suction pipe in the tank to a position near the top. Pipe the return from the heater to the bottom of the tank.

Incorrect installation can cause rapid failure of water tanks due to electrolysis. Tanks must be installed with dialectric connections to electrically isolate the tank from stray current. Note that use of brass or bronze connectors does not replace the need for dialectric connections.