Central Heating: What Cost?
There is no completely ‘cheap’ system of heating. All heating systems cost money to run, but a well-designed system can provide comfort and fair economy. As a rough indication, electrical systems are the most costly to operate, though careful use of off-peak services can bring costs appreciably below costs in situations where electrical appliances are casually used on full-price.
Solid fuel is generally the cheapest, followed by oil and by. However, divisions can never be clear cut, and costs for a smaller home may be marginal between the various types of fuel.
Solid fuels are divided into two main classes: natural, mined fuels, which are cleaned and sized, and processed fuels, made from natural fuels. These are in two forms-carbonization and briquetting. Natural fuels consist of house coal anthracite and Welsh dry steam coal, which are smokeless. House coal may be used with open fires and some types of room heater; dry steam coal is suitable for openable room heaters and boilers.
Both open and closed solid-fuel room heaters can provide hot-water central heating as well as domestic hot water. However, the output of such appliances will not always heat the larger house, and a system of ‘zoning’ to direct heat into rooms of maximum occupation-living rooms by day and bedrooms by night-may be necessary.
Solid-fuel boilers are usually thermostatically controlled and can provide very high levels of heat output.
Where solid-fuel room heaters are used, it is necessary to have independent hot-water heating during summer when the room heater or fire is not in use. This is best provided by an immersion heater, whichinto a boss in the hot-water cylinder.
Open room heaters heat by direct, radiant heat and through a convector grill at the top of the fire. Closed heaters mostly have hoppers which feed fuel by gravity on to the fire. A room heater is normally kept alight through the winter and may need refuelling up to three times in 24 hours. Many high-output heaters have a secondary combustion chamber which effectively ‘consumes’ the smoke products and enables a wider range of fuels to be burnt.
There are three types of solid-fuel boilers-the section, gravity-feed and pot-type boiler. The first is made of cast iron and consists of a number of sections bolted together in relation to the heat output. Fuel is normally fed by hand.
The gravity-feed unit has a steel boiler, is rather more sophisticated and is fed by a hopper. These are usually thermostatically controlled and use an electric fan which produces a heat intense enough to melt the ash into easily removed clinker. Such boilers have a very high utilization of heat – 75 to 80 per cent.
The pot-type boiler is usually thermostatically controlled and consists of a square or circular firebox, surrounded by a cast-iron or welded-steel boiler. This has an efficiency of between 60 and 70 per cent.
Oil-fired boilers fall into three types – the wallflame, the pressure-jet and vapourizing boiler, of which the best-known is the wallflame boiler.
Standard pressure-jet boilers burn a gas oil and are inherently noisy and should be fitted in a boiler house away from the home.
Down-firing pressure-jet boilers can operate on kerosene or gas oil. The kerosene-burning versions are relatively quiet and can be used inside the home. Vapourising boilers use domestic paraffin and are quieter still.
For all oil-fired systems, a large-capacity storage tank is needed which has to be accessible to the supply source. Because of this extra equipment, oil-fired systems are the most expensive to install.
Gas-fired systems merely have the fuel piped into the home from the main supply and have this advantage of convenience. Gas is not always available in rural areas where oil may be the best all-round choice of fuel.
Gas boilers offer a choice of balanced, room-sealed or conventional-flue arrangements. This allows a choice of installation position in the home.
10. November 2011 by admin
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