Water Supply Connections - American Standard HPWH50G-AS Owners And Operation Manual

INSTALLATION INSTRUCTIONS
THERMAL EXPANSION
WARNING

WATER SUPPLY CONNECTIONS

Refer to the illustration below (Page 16) for an example of a suggested typical installation. The installation of unions
or flexible copper connectors is recommended on the hot and cold water connections so that the water heater may
be easily disconnected for servicing if necessary. The HOT and COLD water connections are clearly marked and are
3/4" NPT on all models.
NOTE: Installing a shut-off valve on the cold water line near the water heater will allow for easier
service or maintenance of the unit later.
IMPORTANT: Do not apply heat to the HOT or COLD water connections. If sweat connections are
used, sweat tubing to adapter before fitting the adapter to the cold water connections on heater. Any
heat applied to the hot or cold water connection will permanently damage the dip tube.
The water heater should not be installed in a space where liquids which give off
flammable vapors are used or stored. Determine if a check valve exists on the inlet
water line. It may have been installed on the cold water line as a separate backflow
prevention device, or it may be part of a pressure-reducing valve, water meter or
water softener.
A check valve located in the cold water inlet line can cause what is referred to as a
"closed water system." A cold water inlet line with no check valve or backflow
prevention device is referred to as an "open" water system. As water is heated, it
expands in volume and creates an increase in the pressure within the water system.
This action is referred to as "thermal expansion." In an "open" water system,
expanding water which exceeds the capacity of the water heater flows back into the
city main where the pressure is easily dissipated.
A "closed water system," however, prevents the expanding water from flowing
back into the main supply line, and the result of "thermal expansion" can create a
rapid and dangerous pressure increase in the water heater and system piping. This
rapid pressure increase can quickly reach the safety setting of the relief valve,
causing it to operate during each heating cycle.
Thermal expansion, and the resulting rapid and repeated expansion and contraction
of components in the water heater and piping system, can cause premature failure
of the relief valve, and possibly the heater itself. Replacing the relief valve will not
correct the problem!
The suggested method of controlling thermal expansion is to install an expansion
tank on the cold water line between the water heater and the check valve (refer to
the illustration on page 16). The expansion tank is designed with an air cushion built
in that compresses as the system pressure increases, thereby relieving the excess
pressure condition and eliminating the repeated operation of the relief valve. Other
methods of controlling thermal expansion are also available. Contact your installing
contractor, water supplier or plumbing inspector for additional information
regarding this subject.
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