Space Heating And Potable Water System; Closed Water Systems; Thermal Expansion - American Water Heater 300 Series Instruction Manual

SPACE HEATING AND POTABLE WATER SYSTEM

Your water heater is equipped with inlet/outlet connections for use
in space heating applications (see Figure 10). If this water heater
is to be used to supply both space heating and potable (drinking)
water, the instructions listed below must be followed:
• Be sure to follow the manual(s) shipped with the air handler or
other type heating system.
• This water heater cannot be used in space heating applications
only.
• This water heater is not to be used as a replacement for an
existing boiler installation.
• Do not use with piping that has been treated with chromates,
boiler seal or other chemicals and do not add any chemicals to
the water heater piping
• If the space heating system requires water temperatures in excess
of 120°F, a mixing valve must be installed per the manufacturer's
instructions in the potable hot water supply to limit the risk of scald
injury.
• Pumps, valves, piping and fittings must be compatible with
potable water.
• A properly installed flow control valve is required to prevent
thermosiphoning. Thermosiphoning is the result of a continuous
flow of water through the air handler circuit during the off cycle.
Weeping (blow off) of the temperature and pressure relief valve
(T & P relief valve) or higher than normal water temperatures are
the first signs of thermosiphoning.
• The hot water line from the water heater should be vertical past
any mixing valve or supply line to the heating system to remove
air bubbles from the system Do not connect the water heater to
any system or components previously used with non-potable
water heating appliances when used to supply potable water.
Figure 10

CLOSED WATER SYSTEMS

Water supply systems may, because of code requirements or such
conditions as high line pressure, among others, have installed
devices such as pressure reducing valves, check valves, and back
flow preventers. Devices such as these cause the water system to
be a closed system.

THERMAL EXPANSION

As water is heated, it expands (thermal expansion). In a closed
system the volume of water will grow when it is heated. As the
volume of water grows there will be a corresponding increase in
water pressure due to thermal expansion. Thermal expansion can
cause premature tank failure (leakage). This type of failure is not
covered under the limited warranty. Thermal expansion can also
cause intermittent temperature-pressure relief valve operation:
water discharged from the valve due to excessive pressure build
up. This condition is not covered under the limited warranty. The
temperature-pressure relief valve is not intended for the constant
relief of thermal expansion.
A properly sized thermal expansion tank should be installed on all
closed systems to control the harmful effects of thermal expansion.
Contact a local plumbing service agency to have a thermal
expansion tank installed.
NOTE: To protect against untimely corrosion of hot and cold
water fittings, it is strongly recommended that di-electric unions
or couplings be installed on this water heater when connected
to copper pipe, see Figure 11 also.
Figure 11 show the typical attachment of the water piping to
the water heater. The water heater is equipped with 3/4 inch
NPT water connections for 50 gallon unit and 1 inch NPT water
connections for 75 gallon unit..
NOTE: If using copper tubing, solder tubing to an adapter before
attaching the adapter to the water heater connections. Do not
solder the water lines directly to the water heater connections.
It will harm the dip tube and damage the tank, T & P Valve and
Pipe Insulation (if supplied)
Fit pipe insulation over the incoming cold water line and the hot
water line. Make sure that the insulation is against the top cover of
the heater. Fit T & P valve insulation over valve. Make sure that the
insulation does not interfere with the lever of the T & P valve.
Secure all insulation using tape.
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Figure 11