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.

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 safe and correct installation and operation of this water heater.

Figure 16

Typical Tempering Valve Installation

Combination Space Heating/Potable

Water Heating System

Domestic	Must be vertical to
Hot Water
Hot Water
Out	remove air bubbles
Tempering	Cold
Valve	Cold	Flow Control
	Water	Pump Valve
	Inlet	Pump Valve

Hot		Out
Water		Out	In
Water			In
Out		Coil
Unions	To	Coil
Unions	To
	Air
	Handler
		Air
	Shut-off	Handler
	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.