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Some jurisdictions may require a backflow preventer in
the incoming cold water line. This may cause the
temperature and pressure relief valve on the water
heater to discharge or weep due to expansion of the
heated water. A diaphragm-type expansion tank
suitable for potable water will normally eliminate this
weeping condition. Please read and follow the
manufacturer’s instructions for the installation of such
tanks.
Also see “Water System Piping” (Page 12) for
additional instructions on the safe and correct
installation and operation of this water heater.
Special Applications
Combination Space Heating/Potable
Water System
Some water heater models are equipped with
inlet/outlet tappings for use with space heating
applications. If this water heater is to be used to supply
both space heating and domestic potable (drinking)
water, the instructions listed below must be followed.
!
Be sure to follow the manual(s) shipped with the air
handler system.
!
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 tempering valve
or an anti-scald device should be installed per its
manufacturer’s instructions in the domestic
(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) or higher than normal water temperatures
are the first signs of thermosiphoning.
!
The domestic hot water line from the water heater
should be vertical past any tempering valve or
supply line to the air handler to remove air bubbles
from the system. Otherwise, these bubbles will be
trapped in the air handler heat exchanger coil,
reducing the efficiency.
!
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.
15
Coil
Must be vertical to
remove air bubbles
Figure 16
Typical Tempering Valve Installation
Combination Space Heating/Potable
Water Heating System
Domestic
Hot Water
Out
Tempering
Valve
Hot
Water
Out
Unions
Cold
Water
Inlet
Pump
Flow Control
Valve
To
Air
Handler
Out
In
Air
Handler
Shut-off
Valve
Massachusetts code
does not allow this
type of installation.
Solar Installation
If this water heater is used as a solar storage heater or
as a backup for the solar system, the water supply
temperatures to the water heater tank may be in excess
of 120°F. A tempering valve or other temperature
limiting valve must be installed in the water supply line
to limit the supply temperature to 120°F.
Note: Solar water heating systems can often supply
water with temperatures exceeding 180°F and may
result in water heater malfunction.