Special applications, Combination space heating/potable water system, Solar installation – American Water Heater 318935-003 User Manual

Page 15

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15

Special Applications

Combination Space Heating/Potable
Water System

Some water heater models are equipped with inlet/outlet
tappings suitable for combination water (potable) heating
and space heating and not suitable for space heating
applications only. 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 tempera-
tures in excess of 120°F, a mixing 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 pre-
vent 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 mixing valve or supply line
to the air handler to remove air bubbles from the sys-
tem. 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.

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” section for additional
instructions on the proper installation and operation of this
water heater.

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 mixing valve or other temperature limiting valve
must be installed in the water supply line to limit the supply
temperature to 120°F. The unit must be set to Standard
Mode (See Operating the Temperature Control System
section).
NOTE: Solar water heating systems can often supply water
with temperatures exceeding 180°F and may result in water
heater malfunction.

Figure 16

Typical Mixing Valve Installation

Combination Space Heating/Potable

Water Heating System

Metal Drain Pan Floor Drain

Unions

Mixing

Valve

Coil

Air

Handler

Shut-off

Valve

To

Air

Handler

Massachusetts code

does not allow this

type of installation.

Pump

Flow Control

Valve

In

Out

Domestic

Hot Water

Out

Cold

Water

Inlet

Hot

Water

Out

6" Maximum

Air Gap

Discharge Pipe

Do Not Cap or Plug

Must be vertical to

remove air bubbles

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