Closed System/Thermal Expansion; Temperature And Pressure Relief Valve - Sears Kenmore 153.576300 Use & Care Manual

Closed System/Thermal Expansion

As water is heated, it expands (thermal expansion). In a closed
system, the volume of water will increase. As the volume of
water increases, there will be a corresponding increase in water
pressure due to thermal expansion. Thermal expansion can
cause premature tank failure (leakage). This type of failure is not
covered under the limited warranty. Thermal expansion can also
cause intermittent temperature-pressure relief valve operation:
water discharged from the valve due to excessive pressure build
up. The temperature-pressure relief valve is not intended for the
constant relief of thermal expansion. This condition is not covered
under the limited warranty.
A properly sized thermal expansion tank should be installed
on all closed systems to control the harmful effects of thermal
expansion. Thermal expansion tanks are available from Sears
stores and through the Sears Service Centers. Contact the
local plumbing inspector, water supplier and/or the Sears
Service Center for assistance in controlling these situations.
(For additional information, see the Troubleshooting Guide later
in this manual.)

Temperature and Pressure Relief Valve

1"minimum
Do Not Cap or Plug
Metal
Drain Pan
Drain
FIGURE 24.
Explosion Hazard
Temperature and Pressure Relief (T&P)
Valve (Optional Top T&P Relief
Valve Not shown)
Discharge Pipe
Drain line 3/4"
ID minimum
6" Maximum
Air Gap
For protection against excessive pressures and temperatures,
a temperature and pressure relief valve must be installed in the
opening marked "T & P RELIEF VALVE." (See Figure 24). This
valve must be design certified by a nationally recognized testing
laboratory that maintains periodic inspection of the production
of listed equipment or materials as meeting the requirements
for Relief Valves for Hot Water Supply Systems, ANSI Z21.22.
The function of the temperature and pressure relief valve is to
discharge water in large quantities in the event of excessive
temperature or pressure developing in the water heater. The
valve's relief pressure must not exceed the working pressure of
the water heater as stated on the rating plate.
IMPORTANT: Only a new temperature and pressure relief valve
should be used with your water heater. Do not use an old or
existing valve as it may be damaged or not adequate for the
working pressure of the new water heater. Do not place any
valve between the relief valve and the tank.
The Temperature & Pressure Relief Valve:
• Must not be in contact with any electrical part.
• Must be connected to an adequate discharge line.
• Must not be rated higher than the working pressure shown
on the rating plate of the water heater.
The Discharge Line:
• Must not be smaller than the pipe size of the relief valve or
have any reducing coupling installed in the discharge line.
• Must not be capped, blocked, plugged or contain any valve
between the relief valve and the end of the discharge line.
• Must terminate a maximum of six inches above a floor
drain or external to the building. In cold climates, it is
recommended that the discharge line be terminated at an
adequate drain inside the building.
• Must be capable of withstanding 250°F (121°C) without distortion.
• Must be installed to allow complete drainage of both the
valve and discharge line.
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