11
FIGURE 9A.
Temperature-Pressure Relief Valve
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 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, 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 = 1,035 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 fitting of the water heater designed for the relief valve.
Position the valve downward and provide tubing so that any
discharge will exit only within 6 inches (153 mm) above, or at
any distance below the structural floor. 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.
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 at an adequate drain.
•
Shall not have any valve between the relief valve and tank.
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.
