PRESSURIZED, FIXED SUPPLY TEMP – CONSTANT SPEED PUMPING
The following piping configuration provides a fixed supply temperature via an adjustable mixing valve and brazed-plate heat exchanger. A heat exchanger separates the system ’ s primary (GARN side) from the secondary (heat distribution) side. The primary pump circulates water between the GARN unit and the heat exchanger; the secondary pump circulates water around the heat distribution piping. When the space calls for heat, controls activate both pumps.
Advantages
Disadvantages
Can be easily connected to a pressurized system. Simple and robust, uses constant speed pumps. The heat exchanger separates the GARN from the heat distribution system, so glycol can be used.
The heat exchanger must be sized and piped properly. Notice the “ counter flow ” configuration on the heat exchanger. See discussion in in the Water to Water Flat Plate Heat Exchanger section of this manual. The strainers must be maintained and cleaned so the heat exchanger does not plug up and lose performance. If the primary pump is improperly sized it can circulate more water than necessary through the GARN unit and the system won ’ t be able to take advantage of thermal stratification.
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Hydronic System Design Manual ©DECTRA CORPORATION - March 2013
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