The existing controls on the domestic hot water system are very simple. DHW heating and recirculation pumps run continuously, and the water heaters <boilers> operate to maintain a fixed storage temperature. As a result, the DHW plant operates at full available capacity, even during unoccupied periods.
We recommend expanding the existing building automation system to include the domestic water heating plant <installing more sophisticated controls to conserve heating and pump energy during unoccupied or low-load periods>. The DHW heating pumps should operate based on demand, so that they shut off when the storage is up to temperature. Storage tank temperatures should be set to the minimum required by local plumbing codes. The recirculation pump should be scheduled off when the building is unoccupied.
Issues and Concerns
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