Instructions / Assembly

9
Thermal Expansion
Determine if a check valve exists in the inlet water
line. Check with your local water utility company.
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 (see 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.
Refer to the following illustration for suggested
typical installation. The installation of unions
or flexible connectors is recommended on the
hot and cold water connections so that the water
heater may be easily disconnected for servicing if
necessary. If flexible water connections are used,
the must comply with the standard for flexible
Water Connectors, ASME A112.18.6/CSA-B125.6.
The HOT and COLD water connections are clearly
marked on the water heater. Install a shutoff valve
in the cold water line near the water heater. Refer
to the following illustration for suggested typical
installation.
Water Supply Connections
IMPORTANT: 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 cold
water connections
on heater. Any heat
applied to the cold
water supply fittings
will permanently
damage the dip tube
and heat traps.
NOTICE: The
National Fuel Gas
Code (NFGC)
mandates a manual
gas shut-off valve:
See (NFGC)
for complete
instructions.
Local codes or
plumbing authority
requirements
may vary from
the instructions
or diagrams
provided and take
precedent over these
instructions.
Typical Installation
Jacket door
Heat trap 6” minimum
Heat trap 6” minimum
To gas supply
Cap
Ground joint union
Drain Pan Pipe
to suitable drain.
To cold water supply
6” Air gap
Blower assembly
1/4” per foot maximum slope up or
down for horizontal venting.
Auxiliary catch pan
Union
Vent connector
Sediment trap
Thermostatic gas valve
Manual gas shut-off
Temperature and
pressure relief valve
Shut-off valve
Shut-off
valve
Thermal expansion tank (if required)
Combustion Air Inlet Openings
Hot water outlet to fixtures
Water Heater Jacket
Relief valve discharge line to
suitable open drain.
Flammable Vapor Sensor
(Not visible in this view.)
Union