A hot water system using a plate heat exchanger (PHE) does not store hot water. The water is heated instantaneously and only when required, so it is intrinsically energy-efficient.
Stokvis series of packaged plate heat exchangers with variable speed pumps can produce hot water instantly and constantly at peak times
A PHE consists of a pack of plates (usually stainless steel) to transfer heat from the primary fluid to the secondary fluid. The plates and gaskets are arranged to form alternating channels between the primary and secondary fluids. Arranged in this way, the plates have an extremely large heat transfer surface area and therefore considerably high loads are achieved from a very compact plate heat exchanger.
For large commercial applications, a PHE is ideal as it is capable of producing hot water instantly and constantly at peak times. Calorifiers and direct-fired water heaters are less reliable and can empty of hot water should higher than normal demands occur.
Plate heat exchangers are easy to maintain. An engineer can usually strip, clean and re-assemble a typical unit within an hour, and they are easy to keep clean.
Because they are non-storage units, PHE's present no risk of contamination of the water with legionella microbes. The water is heated instantly on demand, and therefore the bacteria, which thrive in wet environments at temperatures between about 20 and 50 deg C, have no chance to breed.