Xxx Hydronic loop pumps circulate heating water through the building. These pumps operate as if a constant flow volume is required, but control valves operate to throttle flow and reduce the pumping requirement. Most of the time, except under peak load conditions, the pumps generate a higher head pressure and use more electrical energy than necessary.
We recommend installing variable frequency drives on the heating <chilled water> pumps, and controlling pump speed to maintain a constant pressure at a fixed point in the distribution system. For maximum savings, the pressure setpoint would be adjusted to the lowest setting that will still deliver adequate flow to all areas. Some analysis work would have to be done to identify the best sensing point. Generally, the best energy savings can be achieved by positioning the pressure sensor at a terminal unit rather than at the pumps. <At the same time we also recommend changing existing three-way mixing valves to two-way control valves, in order to reduce flow requirements under partial heating load.>
Issues and Concerns
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