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 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.
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 the heat traps
in the hot/cold nipples.
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
Heat trap 6” minimum
Heat trap 6” minimum
Union
To gas supply
Sediment trap
Cap
Ground joint union
Drain Pan Pipe to suitable drain.
Relief valve discharge
line to suitable open
drain.
To cold water supply
6” Air gap
Draft hood
Pitch up 1/4” per foot
Auxiliary catch pan
Union
Anode
Manual gas shut-off
Thermostatic gas valve
Jacket door
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
Vent connector to
chimney
Drain valve