Thermal Expansion; Temperature-Pressure Relief Valve - A.O. Smith 120 Series Instruction Manual

THERMAL EXPANSION

As water is heated, it expands (thermal expansion). In a closed system
the volume of water will grow when it is heated. As the volume of water
grows 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 valve due to excessive
pressure build up. This condition is not covered under the limited warranty.
The Temperature-Pressure Relief Valve is not intended for constant relief
of thermal expansion.
A properly sized thermal expansion tank must be installed on
all closed systems to control the harmful effects of thermal
expansion. Contact a local plumbing service agency to have a
thermal expansion tank installed.
NOTE: To protect against untimely corrosion of hot and cold water
fittings, it is strongly recommended that di-electric unions or couplings
be installed on this water heater when connected to copper pipe.
All gas piping must comply with local codes and ordinances or with the
National Fuel Gas Code (ANSI Z223.1/ NFPA-54). Copper and brass tubing
and fittings (except tin lined copper tubing) should not be used.
FIGURE 10.
Figure 10 shows typical attachment of water piping to the water heater.
The water heater is equipped with 3/4 inch NPT water connections.
NOTE: If using copper tubing, solder tubing to an adapter before
attaching the adapter to the water heater connections. Do not solder
the water lines directly to the water heater connections. It will harm
the dip tube and damage the tank.
T & P Valve and Pipe Insulation
1. Locate the temperature and pressure relief valve on the water heater
(also known as a T&P relief valve). See Figure 11.
2. Locate the slit running the length of the T&P relief valve insulation.
3. Spread the slit open and fit the insulation over the T&P relief valve. See
Figure 11. Apply gentle pressure to the insulation to ensure that it is fully
seated on the T&P Relief Valve. Once seated, secure the insulation with
duct tape, electrical tape, or equivalent. IMPORTANT: The insulation
and tape must not block the discharge opening or hinder access to the
manual relief lever (Figure 11). Ensure a discharge pipe is installed into
the T&P valve discharge opening per the instructions in this manual.
4. Locate the hot water (outlet) & cold water (inlet) pipes to the water heater.
5. Locate the slit running the length of a section of pipe insulation.
6. Spread the slit open and slip the insulation over the cold water (inlet)
pipe. Apply gentle pressure along the length of the insulation to ensure
that it is fully seated around the pipe. Also, ensure that the base of
the insulation is flush with the water heater. Once seated, secure the
insulation with duct tape, electrical tape, or equivalent.
7. Repeat steps 5 and 6 for the hot water (outlet) pipe.
8. Add additional sections of pipe insulation as needed.

TEMPERATURE-PRESSURE RELIEF VALVE

This water heater is provided with a properly rated/sized and certified
combination Temperature-Pressure Relief Valve (T&P 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
for Hot Water Supply Systems, ANSI Z21.22 • CSA 4.4, and the code
requirements of ASME.
If replaced, the new T&P valve must meet the requirements of local
codes, but not less than a combination Temperature-Pressure Relief
Valve rated/sized and certified as indicated in the above paragraph.
The new 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 Btu/hr or kW input rate as shown on the water heater's model
rating plate.
Note: In addition to the factory installed Temperature-Pressure Relief
Valve on the water heater, each remote storage tank that may be
installed and piped to a water heating appliance must also have its
own properly sized, rated and approved Temperature-Pressure Relief
Valve installed. Call the toll free technical support phone number listed
on the back cover of this manual for technical assistance in sizing a
Temperature-Pressure Relief Valve for remote storage tanks.
For safe operation of the water heater, the Temperature-Pressure
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. Install discharge piping so that any discharge will exit the
pipe within 6 inches (15.2 cm) above an adequate floor drain,
or external to the building. In cold climates it is recommended
that it be terminated at an adequate drain inside the building. Be
certain that no contact is made with any live electrical part. The
15
FIGURE 11.
Explosion Hazard
Temperature-Pressure Relief Valve
must comply with ANSI Z21.22-
CSA 4.4 and ASME code.
Properly sized Temperature-Pressure
Relief Valve must be installed in
opening provided.
Can result in overheating and
excessive tank pressure.
Can cause serious injury or death.