Boiler emergency repairs
How your boiler and hot water work
There are several different ways to provide hot water and central heating. Traditionally, the hot taps are supplied from a hot water storage cylinder, which in turn draws from a cold water storage cistern in the roof space. Water is heated in the cylinder by a fitted immersion heater and/or indirectly by a boiler. Hot water is drawn as needed from that stored in the cylinder.
Combi (combination) boilers
Combi (combination) boilers are increasingly popular, especially in flats and small houses where space is limited, as they cut out the need for a hot water cylinder. They are supplied from the rising main, so no storage cistern is needed, and they provide water heating and central heating in a single unit.
Older houses and flat conversions sometimes have instantaneous gas multipoint heaters fed directly from the rising main, which only light when a hot tap is opened. There is no energy lost from a storage cylinder, so these systems are quite efficient when a substantial amount of water is drawn off. They are not so good, however, when used in quick bursts, for example to wash hands or rinse a cup. As most people now want central heating as well as hot water, they have been largely superseded by combi (combination) boilers.
How a combi boiler works
There are two circuits, so the dirty water that circulates through the radiators does not mix with the domestic hot water (DHW) going to the taps. A diverter valve switches heat from the radiators to the DHW as required. Returning cooler water goes back into the boiler for reheating, and the circulator keeps it all moving. When a tap is opened, cold water runs through the heat exchanger and is heated, but as it does so the temperature of the boiler falls and a thermostat triggers the diverter valve, so hot water from the boiler is sent back into it instead of to the radiators.
A boiler like this will supply hot water quickly when the heating is already on. When the heating is off, a different system comes into action. Opening a tap causes a pressure drop in the pressure vessel. This operates a switch, which fires the boiler. This takes a few seconds longer, and to counter that, some boilers have a small hot water storage vessel built in, ready for immediate use. Combi boilers are usually gas-fired, but there are oil-fired versions too.
When any part of that system fails, our Gas Safe registered engineers will find the fault and put it right. Whether it is a combi, system or regular boiler, call us for emergency plumbing in Woking or get in touch to arrange a visit.
