DOMESTIC HOT WATER
Domestic Hot Water
Many residential homes and small commercial buildings have two hot water systems; a heating system and a domestic hot water system (DHW). As the words entail; the heating system is used to provide heat to the building during cold weather. The domestic hot water system (DHW) is used to provide hot water for the kitchen and bathroom sinks, tubs and other appliances. The same boiler can provide both water systems as long as both water systems do not mix. That is the water that circulate through the heating system cannot be circulated through the domestic hot water system.
Domestic hot water can be supplied through a stand-alone water heater or an indirect water heater (a tank with a coil) that is heated using a boiler. A stand-alone water heater can be instantaneous or a hot water storage tank. Instantaneous water heaters have no storage capacity. The heater fires up and heats the water when someone opens any of the hot water faucets. On the other hand, the hot water storage tank will heat the water and store it for later use. The indirect water heater is a storage tank with a coil in the middle. The hot boiler water is ran through the tank coil to heat the tank water surrounding the coil. That tank water is used as domestic hot water.