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 illustration below 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
Water heater jacket
Temperature and
pressure relief valve
To gas supply
Sediment trap
Combination gas control
(Thermostat)
Cap
Jacket door
Flammable vapor sensor
Manual gas
shutoff valve
Auxiliary drain pan
Drain pan pipe to
suitable drain
6" Air gap
(15.2 cm)
Drain Valve
Relief valve
discharge line to
suitable open drain
Thermal expansion
tank (if required)
Shutoff
valve
Union
Transformer box
(Remote control models only)
Blower assembly
Anode
1/8" per foot (10 mm per meter)
maximum slope up or down for
horizontal venting
Shutoff valve
Heat trap 6" (15.2 cm) minimum
To cold water supply
Combustion
air inlet openings
Union
Vent connector
Union
Heat trap 6” minimum
(15.2 cm)
Hot water outlet
to fixtures