Instructions / Assembly

11
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. 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.
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.
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.
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.
Alternate sediment
trap location
To gas supply
To gas supply
To cold water supply
Relief valve discharge line
to suitable drain
Sediment trap
Drain valve
Manual gas shut-off
Sediment trap
Ground joint union or ANSI design
certified semi-rigid or flexible gas
appliance connector
Thermostat
Jacket door
Anode
Temperature and
pressure relief valve
Flue baffle
(underneath)
Roof jack
Hot water outlet to fixtures
Typical Installation