Space Heating And Potable Water System; Combo Heating Inlet And Outlet Side Taps; Combo Heating; System Requirements - A.O. Smith 100 Series Installation And Operating Manual

storage tank temperature five degrees lower than the water
heater's temperature setting. Using the plug valve, adjust
the flow in the recirculating line to five gallons per minute.

SPACE HEATING AND POTABLE WATER SYSTEM

Figure 38. Water Heater with Side Taps for Space Heating
This appliance has been design certified as complying with CSA
Standards for water heaters and is suitable for combination water
(potable) heating and space heating but not space heating only
applications.
Note: When there will be no domestic hot water demand for
an extended period of time, the temperature set point
should be set at 32°C (90°F) to prevent "Stacking" and
T&P discharge.
This heater is equipped with additional side taps for use in space
heating applications. See Features and Components (page 8) for
locations. If this water heater is to be used to supply both space
heating and potable (drinking) water, the instructions listed below
must be followed:
WARNING
Toxic Chemical Hazard
• Do not connect to non-potable water system.
Consult a Qualified Installer or Service Agency. Follow manufacturer's
instructions for installation of valves. Before changing the factory
setting on the control system, seeTemperature Regulation (page 38).
Note: Water piping and vent piping occupy the space above the
water heater. Plan the water piping to ensure it does not
cause interference with the vent piping. See Planning the Vent
System (page 14).
If this water heater is to be used to supply both space heating and
potable 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 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.
• When the system requires water for space heating at
temperatures higher than required for domestic water
purposes, a mixing valve must be installed. See Figure 35 (page
29).
• If the space heating system requires water temperatures in
excess of 120°F, install a Thermostatic Mixing Valve in the
domestic (potable) hot water supply at each point-of-use to
limit the risk of scald injury. See Figure 35 (page 29).
• 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-pressure
relief valve (T&P) 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.

COMBO HEATING INLET AND OUTLET SIDE TAPS

Your water heater is equipped with Combo Heating capabilities
with the two side plumbing taps PLUGGED (items 24 and item 29
in Features and Components (page 8)). See also Figure 38 (page
32). If the heater is to be operated using the side taps for combo
heating, these plugs must be removed.

COMBO HEATING

This section serves as a guide for the installation and use of
"Combo" heating systems utilizing a domestic water heater that
has been specifically approved for such use. It is written for those
knowledgeable in the required trades and professionals involved
in the design and installation of Combo Heating Systems.
It is the responsibility of the installer/designer to follow all applicable
codes to ensure the effectiveness and safety of the installation.

SYSTEM REQUIREMENTS

The following requirements must be met for the installation of
Combo Heating Systems:
1. All components used for the distribution of water in the heating
loop must be suitable for potable water. These include all
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