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6
Installing the water heater.
Typical Installation
Thermal Expansion
Determine if a check valve exists in the
inlet water line. Check with your local
water utility. It may have been installed in
the cold water line as a separate back flow
preventer, 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 back
flow 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 in the cold water line between the
water heater and the check valve (refer
to the illustration below). The expansion
tank is designed with an air cushion built
in that compresses as the system pressure
increases, thereby relieving the over
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.
NOTICE: DO NOT apply
heat to the HOT or COLD
water connections. If sweat
connections are used, sweat
tubing to adapter before
fitting adapter to the water
connections on heater.
Any heat applied to the
water supply fittings will
permanently damage the
dip tube and/or heat traps.
Water Supply Connections
Refer to the illustration below for 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. Install a shut-off valve
in the cold water line near the water heater.
Heat trap
6" min imu m
Heat trap
6" min imu m
6" a ir g ap
To electrical
distrib ution panel
Ho t water outlet
to fixtu res
Electrical junction box
(use only copper conductors)
Jacket access
pane ls
Relief valve disch arg e line
to suit ab le op e n d rain
Sh u t -o ff
valve
Th e rm a l
expansion tank
(if req uired )
To cold water
supply
Un io n
Temperature
&
Pressure
Relief Valve
Un io n
An o d e
Drain valve
Auxiliary catch pan
2" maximum
Figure 2
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