Ao-smith 315795-000 MH User Manual download pdf (Page 15)

T&P Relief Valve

Drain Line

Manual Relief Lever

T&P Relief Valve Insulation

FIGURE 25.

TEMPERATURE-PRESSURE RELIEF VALVE

This heater is provided with a properly certified combination

temperature - pressure relief valve by the manufacturer.

The valve is certiﬁ ed by a nationally recognized testing laboratory

that maintains periodic inspection of production of listed equipment

of materials as meeting the requirements for Relief Valves and

Automatic Gas Shut-off Devices for Hot Water Supply Systems,

ANSI Z21.22 • CSA 4.4.

If replaced, the valve must meet the requirements of local codes, but

not less than a combination temperature and pressure relief valve

certiﬁ ed as indicated in the above paragraph.

The valve must be marked with a maximum set pressure not to

exceed the marked hydrostatic working pressure of the water heater

(150 psi = 1,035 kPa) and a discharge capacity not less than the

water heater input rate as shown on the model rating plate.

For safe operation of the water heater, the relief valve must not be

removed from its designated opening nor plugged.

The temperature-pressure relief valve must be installed directly into

the ﬁ tting of the water heater designed for the relief valve. Position

the valve downward and provide tubing so that any discharge will

exit only at any distance below the structural ﬂ oor and external to

the building. In cold climates, it is recommended that the discharge

pipe be terminated at an adequate drain inside the building. Be

certain that no contact is made with any live electrical part. The

discharge opening must not be blocked or reduced in size under

any circumstances. Excessive length, over 30 feet (9.14 m), or

use of more than four elbows can cause restriction and reduce the

discharge capacity of the valve, see Figure 26.

No valve or other obstruction is to be placed between the relief valve

and the tank. Do not connect tubing directly to discharge drain

unless a 6 inch (15 cm) air gap is provided. To prevent bodily injury,

hazard to life, or property damage, the relief valve must be allowed to

discharge water in quantities should circumstances demand. If the

discharge pipe is not connected to a drain or other suitable means,

the water ﬂ ow may cause property damage.

The Discharge Pipe:

• Shall not be smaller in size than the outlet pipe size of the valve, or

have any reducing couplings or other restrictions.

• Shall not be plugged or blocked.

• Shall be of material listed for hot water distribution.

• Shall be installed so as to allow complete drainage of both the

temperature-pressure relief valve, and the discharge pipe.

• Shall exit only at any distance below the structural ﬂ oor and

external to the building. In cold climates, it is recommended that

the discharge pipe be terminated at an adequate drain inside the

building.

• Shall not have any valve between the relief valve and tank.

• Temperature-pressure relief valve

must comply with ANSI Z21.22-

CSA 4.4 and ASME code.

• Properly sized temperature-relief

valve must be installed in opening

provided.

• Can result in overheating and

excessive tank pressure.

• Can cause serious injury or

death.

The temperature-pressure relief valve must be manually operated

at least once a year. Caution should be taken to ensure that (1) no

one is in front of or around the outlet of the temperature-pressure

relief valve discharge line, and (2) the water manually discharged

will not cause any bodily injury or property damage because the

water may be extremely hot.

If after manually operating the valve, it fails to completely reset and

continues to release water, immediately close the cold water inlet

to the water heater, follow the draining instructions, and replace the

temperature-pressure relief valve with a new one.

FIGURE 26.

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 55 56

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Ao-smith 315795-000 MH User Manual Page 15

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