A circulating pump works by pumping or circulating liquids, gases or slurries in a loop or closed circuit. Their most common application is circulating water in a hydronic cooling or heating system. Since the materials that they pump move around in closed circuits, they do not expend lot of energy. For example, when water is initially pumped upwards, it circulates around a system and eventually returns to its original position. From this point, a pump only needs enough power to counteract the drag or inertia in pipes to propel the water forward efficiently. This process is repeated over and over again.
Since they require little energy to function, circulating pumps designed for homes are small enough to fit alongside plumbing systems.
Circulating pumps for home use are typically compact electrically powered centrifugal pumps. In general, their sole purpose is to produce hot water on demand. Without them, users will have to wait for some time for water to heat each time they turn on dedicated taps. The three main components of a circulating pump are:
- Support bearings
- Pump impeller
- Motor rotor
An electric motor rotor powers the impeller, which then thrusts the water forward or upward. An impeller is like a turbine in that it's a wheel with a series of angled blades. The impeller spins extremely fast, pushing water out and compressing it. The motor is sealed in a waterproof casing and is connected to the impeller. While circulating pumps are small enough to be mounted alongside plumbing systems, industrial type pumps have large designs and motors are usually fixed on separate locations away from the piping system.
Hot Water Recycling
One of the most common purposes of home use circulating pumps is to eliminate the wait for water to heat once a tap is turned on. In a typical hot water system, hot water is produced by the heater and flows through the pipes and then to the taps. Once the taps are turned off, the hot water in the pipes cools off. The heater system will only heat water once a tap is turned on again, which would require some time and cause water wastage. With a circulating pump, the wait for water to heat is eliminated and a steady supply of hot water is ensured all the time. Energy consumption is minimal and little water is wasted. They are also ideal for areas where water is in limited supply.
Home use pumps are typically made of bronze to prevent corrosion, since oxygenated potable water flows through them constantly.
Solar Water Heating
Another popular and relatively new application for circulating pumps is in solar water heating systems. In this set-up, water is pumped to the solar collector, where it will be heated. That water then moves its way to a water tank, where heat is passed on to the water. The pump will again send cooler water back to the solar collector for heating.