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Temperature-Pressure Relief Valve
Explosion Harzard
-
This heater is provided with a properly certified combination
temperature - pressure relief valve by the manufacturer.
The valve is certified by a nationally recognized testing laboratory
that maintains periodic inspection of production of listed
equipment as meeting the requirements for Relief Valves for Hot
Water Supply Systems, ANSI Z21.22 and the code requirements
of ASME.
If replaced, the valve must meet the requirements of local codes,
but not less than a combination temperature and pressure relief
valve certified 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 = 1,035kPa) 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 fitting of the water heater designed for the relief valve.
Position the valve opening downward and provide tubing so
that any discharge will exit only within 6 inches (15.3 cm)
above, or at any distance below the structural floor, see Figure
16. 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.
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 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 flow may cause property damage.
COLD WATER
HOT WATER
INLET
OUTLET
SHUTOFF
VALVE
COLD
HOT
DRAFT HOOD
TEMPERATURE - PRESSURE
RELIEF VALVE
(OPTIONAL TOP T&P RELIEF
VALVE NOT SHOWN)
DISCHARGE PIPE
(Do not cap or plug)
DRAIN VALVE
6” MAXIMUM
AIR GAP
FLOOR DRAIN
FIGURE 16.
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 terminate a maximum of six inches above a floor drain
or external to the building. In cold climates, it is recommended
that the discharge pipe be terminated at an adequate drain
inside the building.
• Shall terminate at an adequate drain.
• Shall not have any valve between the relief valve and tank.
Page 15
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