DIFFERENT METHODS OF HEATING AND VENTILATION

Various methods of heating have been evolved and are in use at the present day, and a knowledge of the characteristics and relative costs is necessary in making a selection of the most suitable type for any particular building.

There are two main divisions of heating systems: direct and indirect. Direct systems are those in which the fuel is consumed in the room to be heated. Indirect systems are those in which the fuel is consumed outside the room, the heat being conveyed to the room by a medium such as steam or hot water.

Direct systems are chiefly used for intermittent heating isolated rooms. They may be summarized thus –

System	Advantages	Disadvantages	Efficiency
Open fires, burning coal or coke	Comfortable appearance in living rooms. Largely radiant heat, ventilation effect strong. Cheap in first cost.	Require flues. Coal and ashes to be carried about, causing dust and dirt.Unsatisfactory in large rooms.	About 25%
Slow combustions stoves, burning coke or anthracite.	Steady warmth, partly radiant, but chiefly convected. Suitable for hutments and temporary buildings. Cheap to install.	Fumes sometimes Given off. Coke and ashes to be carried about. Considerable labour involved for a large number.	About 50%
Gas fires	Easily lit, quick response, heat largely radiant, ventilation effect.	Small flue necessary. Intense radiation drying to skin.	About 50%
Gas convectors	Useful for background warming and for halls, small shops etc. No flue needed provided rooms is ventilated	Fumes deleterious if installed in small rooms.	100%
Electric fires	Immediate response. Portable. Require no flue. No fumes. Heat chiefly radiant.	Ventilation not provided. Not suitable for large spaces.	100%
Electric convectors	Most suitable for heating large spaces where central system not possible. Automatic temperature control easily applied.	No disadvantages where this system is suitable. Installation cost comparable with central system.	100%

There are many other forms of Direct Heating, such as gas and electric overhead radiant heaters, in which a metallic plate is heated to a high temperature so as to emit strong heat radiation; and gas and electric unit heaters in which air is delivered to the room by a fan and is warmed in its passage through the unit by heated elements. There are also low- temperature gas and electric radiant panels for fixing to walls, ceilings, etc., also electric tubular heaters for fixing near skirting level (see Fig.9). These systems are generally more expensive in first cost than those enumerated above.

Fig.9. Three –tier “Maxheat” Oval Turbular Electric Heater

Indirect systems are chiefly used for the continuous heating of a number of rooms or large buildings from one central source, hence the name Central Heating. This does not necessarily imply that the heating source is strictly central, indeed it may be at a considerable distance from the building.

This class of system finds its greatest application in large buildings of all types.

The advantages of the Indirect system are – a)Fuel and ashes are kept outside the occupied spaces. B)Individual flues are not required. c)Cleanliness. D)Equable temperature maintained in all parts, easily controlled automatically. The disadvantages are – a) Heat is lost from main piping where this is outside the occupied rooms. This loss can be minimized by proper insulation of the pipes. B)Labour is required for stoking and removal of ashes. This applies only with solid fuel and can be greatly reduced with automatic firing.

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