Many commercial buildings, especially those using generous amounts of hot water like hospitals or hotels, have a closed loop in which hot water is constantly circulated by a small pump. When a tap is open, the hot water is already nearby, and the user does not have to run a copious amount of water before hot water can arrive from the storage tank.
This circulating pump does not need to operate outside of regular business hours. A timer can run the pump a fraction of a full-time cycle. Moreover, less energy is used to heat the water since it is not circulating around the building constantly. If the piping is insulated, the savings will be even more; though even insulated pipe loses some energy.
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Excerpted from Going Green, available as an eBook at this list of eBook retailers online.
