Combo System Basic Principles
Closed/Open Combo System
From the aspect of delivery of domestic hot water and space heating, the Open and Closed systems operate the same. A system becomes closed when a backflow prevention valve or check valve is installed in the cold water piping upstream of the water heater. A backflow prevention valve will prevent the pressure created when water is heated in the water heater, from being relieved into the cold water system.
Therefore, an expansion tank (or equivalent device) may be installed as part of any closed system. The operations of the valve and expansion tank are discussed later in this section of this manual.
Note: Water systems that incorporate a pressure tank (well systems) are normally open systems.
COLD WATER INLET | DOMESTIC HOT WATER |
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CHECK |
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VALVE |
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VALVE |
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(shut off) | SUPPLY AIR | COOLING COIL | SCHEMATIC SYSTEM | |
| (WHEN REQUIRED) |
| (OPTIONAL) | |
EXPANSION TANK |
| VALVE |
| DIAGRAM |
OR OTHER MEANS |
| (shut off) |
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(WHEN REQUIRED) |
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| (Closed Loop System) |
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| RETURN AIR | |
| VALVE | VALVE |
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| (shut off) | (balancing) |
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| CHECK |
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| WATER HEATER | VALVE |
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| HEATING COIL |
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| HRV/ERV CORE |
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| DRAIN |
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| VALVE |
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| BLOWER |
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SCHEMATIC SYSTEM DIAGRAM (Open System)
Note:
Plumbing components and system configuration may vary from diagram portrayed. Refer to local codes, local bylaws and installation manuals supplied with water heater before starting any installation work.
COLD WATER INLET | DOMESTIC HOT WATER |
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VALVE |
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(shut off) | SUPPLY AIR | COOLING COIL | |
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| (OPTIONAL) | |
| (WHEN REQUIRED) |
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| VALVE |
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| (shut off) |
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| RETURN AIR |
| VALVE | VALVE |
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| (shut off) | (balancing) |
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| CHECK |
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| WATER HEATER | VALVE |
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| HEATING COIL |
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| HRV/ERV CORE |
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| DRAIN |
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| VALVE |
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| BLOWER |
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| 5 |
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