Understanding Central Heating Systems

There are three principal systems of central heating:

1 Distribution from a boiler of heated water through pipes terminating in room radiators. The system is commonly termed “wet” central heating.

2 Warm air. In this system air, instead of water, is heated and circulated through the house.

3 Heated structures, a system which includes underfloor heating, ceiling heating, storage radiators and storage fan heaters.

Wet central heating

Water is heated in a boiler (gas, oil or solid fuel) or in an electrically heated storage tank and is circulated through pipes to radiators, fan convectors or skirting heaters.

Small bore. The modern form of “wet” central heating is termed small-bore because copper pipes of small diameter, usually ½ in. (2.5cm), supply the hot water radiators. From the boiler the hot water is forced through the pipework by an electric circulating pump.

Micro-bore. In this variant of the small-bore system even smaller-diameter pipes are run to the radiators from manifolds in the pipework.

Radiators. Like the pipes, radiators used in the small-bore system are far less obtrusive than before the advent of small-bore. They are slim in profile and there are designs that will fit around bay windows. The actual size (heated surface area) of each radiator should be governed by the size and heat requirements of the room it serves. Heat output from the radiator can be controlled by manually turning the radiator valve. Alternatively, thermostatic valves can be set to adjust output automatically. Some radiators incorporate fans so that a room can be .heated up from cold very rapidly.

All types should be fitted with valves. By turning off the valve you turn off the water. This allows you to ease away the radiator and clean or redecorate the wall behind it. Radiators are best placed under windows where they intercept cold air entering through the windows. Installation. The installation of a small-bore heating system is within the capacity of a determined do-it-yourself enthusiast. But if you intend to tackle the job yourself, seek’ professional advice beforehand to ensure that the pipe layout and distribution of radiators is tailored adequately to your house. You can buy an entire central heating kit that includes the boiler, controls, pipe-work and radiators with detailed installation instructions.

You can run the small-bore copper pipes along the tops of skirting and, where necessary, pass them through holes in partition walls that you make with an electric drill. Fittings to the pipe, such as elbows, bends and tees, are of the compression or capillary type so that you need only a spanner or blowlamp to secure them

Warm air central heating

Warm air systems cut out the middle stage of the piped water (or “wet”) system. The air is heated by a central unit and fanned or convected straight into the other rooms of the house by means of ducts. Since ducting involves the- house structure, warm air central heating is best built into a new house as it is constructed.

Fully ducted. A fully ducted version of the system is connected to every room in the house and, in addition to blowing out warm air, draws back stale air to clean it before it is recirculated.

Stub duct. A modified, or stub duct, version normally has outlets downstairs in the living area and convection heats upstairs rooms.

Gas, oil or solid fuel can power fully ducted or stub duct versions but electricity is most suitable. An electrical heating unit, a tall box with grills, can be sited anywhere in the house, since no flue is needed. It uses the cheaper tariff White Meter electricity, which is stored up overnight for daytime use.

Heated structures

This system of central heating includes underfloor heating, ceiling heating and storage radiators.

Underfloor heating. Heating coils must be embedded in a floor base such as concrete that will store the heat for radiation upwards into the room and be sufficiently insulated to prevent the heat from escaping down into the ground. Underfloor heating uses off-peak (comparatively economical) electricity but any daytime boost will expend day-rate electricity. Most types of floor-covering, including wall-to-wall carpets, can be laid over the heated floor without effectively reducing the warmth radiated. Because underfloor heating depends on the right kind of floor base, it is best incorporated in new houses or conversions.

Ceiling heating is similar to floor warming in operation but it is a direct acting heating system, which means it uses electricity only when it is producing heat. With this system, heating elements (a series of metal strips or resistance mats pressed between two sheets of special heat resistant material) are fixed above the ceiling surface. Extra thermal insulation is placed immediately above the heating elements to reduce upward heat losses, and most ceiling finishes can be used as the surface only becomes warm — about body temperature — and perfectly safe to touch.

Electric storage heaters. The two types, storage radiators and storage fan heaters, store up heat overnight, when electricity is provided at a cheaper rate on the White Meter tariff, and release heat into the rooms during the following day. They are supplied from a consumer unit in the house separate from that feeding other electrical circuits. A time switch turns power on at the start of the White Meter period and off when it ends. The heaters are made in various sizes to suit the heat requirements of various areas. They can be used for full heating of a room or to give background heating, perhaps in conjunction with direct-acting heaters that can be switched on and off as needed.

Storage radiators. This type of heater emits heat in radiant form through its outer steel casing. You have limited control over the heat output during the day but an input controller can be adjusted to increase or reduce the amount of heat stored overnight and therefore the amount available the following day. Some models have a booster device to extract the last “drop” of stored heat for release towards the end of the day. Storage fan heaters. This type is largely similar to the storage radiator but incorporates a fan that circulates cold air drawn from the room around the heater block and then expels the now warmed air back into the room.

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