Closed System/Thermal Expansion - A.O. Smith GAS WATER HEATER Installation Instructions And Use & Care Manual

IN A CLOSED SYSTEM, USE A
THERMAL EXPANSION TANK
HOT WATER
OUTLET
COLD WATER
INLET VALVE
(SHUT-OFF VALVE)
UNION
TEMPERATURE AND PRESSURE RELIEF VALVE
DISCHARGE PIPE
DO NOT CAP OR PLUG
1" MINIMUM
METAL
DRAIN PAN
1 3/4" DEPTH MAXIMUM
FIGURE 13.
UNTEMPERED
HOT WATER
HOT
WATER
OUTLET
MIXING VALVE
(SET TO 120°F)
FOLLOW THE MIXING
VALVE MANUFACTURER'S
FIGURE 14.
COLD WATER
SUPPLY TO FIXTURES
MAIN WATER SUPPLY
PRESSURE REDUCING
VALVE WITH BYPASS
DRAIN LINE 3/4"
ID MINIMUM
6" MAXIMUM
AIR GAP
MASSACHUSSETTS:
INSTALL A VACUUM RELIEF
IN COLD WATER LINE PER
SECTION 19 MGL 142.
FLOOR DRAIN
TEMPERED WATER
TO FIXTURES
COLD
WATER
INLET
INSTRUCTIONS
Please note the following:
• The system should be installed only with piping that is
suitable for potable (drinkable) water such as copper,
CPVC, or polybutylene. This water heater must not be
installed using iron piping or PVC water piping.
• Use only pumps, valves, or fittings that are compatible
with potable water.
• It is recommend that only full flow ball or gate valves
are used in water piping installations. The use of valves
that may cause excessive restriction to water flow is not
recommended.
• Use only 95/5 tin-antimony or other equivalent solder.
Any lead based solder must not be used.
• Piping that has been treated with chromates, boiler seal,
or other chemicals must not be used.
• Chemicals that may contaminate the potable water
supply must not be added to the piping system.

Closed System/Thermal Expansion

As water is heated, it expands (thermal expansion). In a closed
system, the volume of water will grow. 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 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 effects of thermal expansion.
Contact a plumbing service agency or your retail supplier
regarding the installation of a thermal expansion tank.
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