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
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
Also see “Water System Piping” section for additional instructions on the proper installation and operation of this water heater.
Figure 16 |
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Typical Mixing Valve Installation |
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Combination Space Heating/Potable |
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Water Heating System | Must be vertical to |
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Domestic | remove air bubbles |
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Hot Water | Cold |
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Mixing | Out | Flow Control | |
Valve |
| Water | Valve |
Hot |
| Inlet | Pump |
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| In | |
Water |
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| Out | ||
Out |
| To | |
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Unions | Air |
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Handler | Coil | ||
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| Discharge Pipe |
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| Do Not Cap or Plug |
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| Air | |
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| Handler | |
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| Valve | |
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| 6" Maximum | |
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| Air Gap |
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Metal Drain Pan Floor Drain | Massachusetts code | ||
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| does not allow this |
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| 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 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.
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