In 2004, the first circulation pumps that turn on only when there is a demand were introduced to the multi-family and hospitality industry. These circulation pumps are known as on demand pumps reduce energy required to provide domestic hot water by 30% or more.
Household uses such as showering, cooking or washing clothes in apartments, condominiums, hotels and motels requires a great deal of natural gas, propane, electricity or heating oil. Large boilers or commercial heaters are placed at one central location in a building and the commodity is provided to residents or guests by pumping it through circulation pipes (also known as circulation lines or loop).
Recent studies have shown that people only create a demand about 15% to 20% of the time. Circulation pipes are hot 24 hours a day, seven days a week - even when there is no demand. When the pipes are hot they are continually losing their energy to the ambient environment.
As much as 50% of the energy required to heat water to an acceptable level in a central heating system is lost in the circulation loop.
The answer is to turn the circulation pump off when there is no demand. One solution is to use a timer that turns the pump off at preset times. Unfortunately this requires someone to guess when there will be a demand (this strategy may work in a small apartment or condominium complex but would leave hotel and motel guests less than satisfied).
A better solution is to monitor usage and only turn the pump on when there is a demand. Of course turning off the pump defeats the purpose of having the circulation line in the building in the first place, providing service in a timely manner.
An on demand pump solves this problem because it replaces the existing low speed pump (typically 2 to 7 gpm) and operates at a higher speed (20 to 26 gpm). As soon as a demand is detected by a flow sensor installed in the make-up line (when a faucet is turned on hot water leaves the system and must be made up by the providing utility) the high speed pump rushes hot water through the circulation pipe in a matter of a few seconds.
In tests performed by the California Energy Commission in 2006 on demand pumps reduced energy consumption by an average of 37% in the buildings tested.
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