A hot water exchanger is used in production of domestic hot water. The hot water exchanger can be connected to a district or central heating system.
Hot water exchangers exist as both bolted plate heat exchangers and soldered plate heat exchangers. Other types of exchangers, such as tube heat exchangers also exist. These are however rarely used in domestic hot water production.
In a plate heat exchanger, the cold water passes the heat-bearing medium through small channels. The two liquids are separated by plates. Counter flow heat exchange is applied, which increases the effectiveness of the exchanger, creating a greater cooling of the heat-bearing medium.
Some domestic water exchangers have an extra connection on the secondary side. This allows domestic hot water recirculation to be connected to the exchanger directly.
A domestic hot water exchanger is very compact and effective. The disadvantage is that it demands a relatively large installed heating power capacity, and has a relatively large pressure loss. Furthermore, the plate exchanger is very sensitive to lime deposits. Regular lime removal may therefore be necessary.
As buildings become increasingly energy-efficient their heating demand is reduced. This means that domestic hot water production takes over a larger percentage of the building’s total heat load. Domestic hot water exchangers constitute relatively large heat loads, so many utility companies do not allow them to be used alone.