A.O. Smith 185762-000 - Manual (Page 9)

9
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 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
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 = 1,034.21 kPa) and a discharge capacity not less
than the water heater input rate as shown on the model rating plate
(Electric heaters - watts x 3.412 equal BTU/hr rate).
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 within 6 inches (152.4 mm) above an adequate drain, or
external to the building or structure. 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. The relief valve must be allowed
to discharge water in suffi cient quantities, should circumstances
demand, to prevent bodily injury, hazard to life, or property damage.
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 terminate at an adequate drain.
• Shall not have any shut-off valve between the relief valve and
tank nor in the discharge pipe.
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.
TEMPERATURE-
PRESSURE
RELIEF VALVE
COLD
SHUT-OFF VALVE
UNION
OPTIONAL TOP
T & P LOCATION
HOT
UNION
(OPTIONAL TOP
T & P RELIEF VALVE
NOT SHOWN)
DISCHARGE PIPE
(DO NOT CAP OR PLUG)
6” (152.4 mm) MAXIMUM
AIR GAP
FLOOR DRAIN
DRAIN VALVE
FIGURE 4.