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When DHW is used, a combination boiler stops pumping water to the heating circuit and diverts all the boiler's power to heating DHW. Some combis have small internal water storage vessels combining the energy of the stored water and the gas or oil burner to give faster DHW at the taps or to increase the DHW flow rate.
Condensing boilers are water heaters typically used for heating systems that are fueled by gas or oil. When operated in the correct circumstances, a heating system can achieve high efficiency (greater than 90% on the higher heating value) by condensing water vapour found in the exhaust gases in a heat exchanger to preheat the circulating water.
A common arrangement where hot-water space heating is employed is for a boiler also to heat potable water, providing a continuous supply of hot water without extra equipment. Appliances that can supply both space-heating and domestic hot water are called combination (or combi) boilers. Though on-demand heaters provide a continuous supply of ...
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, [1] [page needed] [2] [page needed] including water heating, central heating, boiler-based power generation, cooking, and sanitation.
Electric heating can either be purely resistance-type heating or make use of a heat pump system to take advantage of low-grade heat in the air or ground. A district heating system uses centrally located boilers or water heaters and circulates heat energy to individual customers by circulating hot water or steam. This has the advantage of a ...
In a closed heating system though, it has no other means of escape and builds up. An air bubble trapped within a radiator means that no hot water circulates in the upper part and so the heating power of the radiator is reduced. If air is trapped within the boiler this may cause pump cavitation or boiling and overheating within the heat exchanger.
The boiler heats water to a temperature controlled by a thermostat. The water then flows (either by natural circulation or by a pump) to radiators in the rooms which are to be heated. Water also flows through a coil in the hot water tank to heat a separate mass of water for bathing, etc.
Heating appliances that use steam or hot water as the fluid are normally referred to as a residential steam boilers or residential hot water boilers. The most common fuel source for modern furnaces in North America and much of Europe is natural gas ; other common fuel sources include LPG (liquefied petroleum gas), fuel oil , wood and in rare ...