To design and install central heating may seem a daunting task, but it can be made reasonably straightforward if kept to a basic system.
There are a number of different types of heating systems. Only a competent handyman should think of designing and installing his own system, but many other people would like to understand more about the system they are ordering, wish to order, or have to maintain. The hardest part is often making the calculations involved in the design.
Planning your own heating system
Before you consider which system to install it is best to make a survey of your home. Draw up a sketch plan as accurately as you can and record these details.
1. Length, height and width of each room, the size of the windows and the height of the sill above the floor, which will help decide the size and position of radiators.
2. The construction, material and thickness of the floors.
3. The construction of the walls, their thickness and whether they are solid or cavity, plastered or masonry.
4. The type of windows, single or double glazed, metal or wooden frames.
5. The construction of ceilings and roof area, whether it is plasterboard or lath, whether it is insulated and to what thickness, and if it is ventilated.
You’ll need to know all of these details accurately to calculate the heat losses which will determine the size of boiler you need, the amount of radiator area and the size of pipes and pump.
6. There is one other major consideration in calculating the heat losses. It is known as the comfort conditions necessary for each room. These are: (a) room temperatures, and (b) air changes or ventilation.
These are explained when we come to calculate heat losses, but they can be marked on your sketch plan.
7. Last, but not least, it is good practice to decide where each piece of equipment will be fixed. If you position these on your sketch it will simplify working out the pipework connections.
Choice of fuel
This is a choice to make before you decide on the boiler or heating appliances. The choice of fuel will affect where the boiler is sited, and will depend on whether there is storage space, on the economic cost of running and, of course, whether there is
fuel service available. You have to weigh up the various advantages and disadvantages of one fuel against another, for your house.
Central heating fuels fall into four main categories.
The first problem with coal is storage. Secondly, the boiler will need cleaning thoroughly and regularly, probably every 24 to 48 hours. You also have to get rid of the ash. Deliveries can be irregular and the control of the heating is not quite so easy as with gas or electricity. It is normal in summer to use an immersion heater for domestic hot water; this is also usually the time when coal can be bought most cheaply.
The immersion heater is electric and is positioned in the boss provided in the hot water cylinder. Coal is not an entirely satisfactory material for providing both heating and hot water throughout the year, unlike the following fuels.
This is not a fuel but an energy generated from a fuel. The supply to a British house is invariably 240 volts, 50 hertz.
Electric space heating can be classified as direct or indirect.
Indirect Known as the storage system, these are heavy radiators filled with refractory blocks which heat up at night on cheap, off-peak electricity and release the stored heat during the day.
Direct Here you use electricity at the standard rate, but it has the advantage of flexibility and immediate response. Electric fires are a direct system.
Direct and indirect systems can be used together and the advantages of electricity are that it is clean, silent, requires little maintenance and you use effectively all the energy you pay for.
However, electric heating can be very expensive indeed to run, and dangerous if not used correctly.
Until ten years ago oil was the most widely used fuel for domestic heating. Unfortunately, oil prices, as the whole world knows, have risen very sharply. You also have to weigh in the balance the uncertainty of delivery and the need to store large quantities of oil, with its inherent smell. Installation costs have proved more expensive than for other fuels. For these reasons oil has taken second place to gas in recent years.
Since heat will transfer from one room to another and may produce cold areas. Partial heating may be installed so that more heaters can be incorporated into the system later. If you want to do this be sure to allow for the heating load in the design stage.
Background heating can be full central heating with reduced temperatures in some or all rooms. This system can be topped up by using off-peak electric heaters, gas fires and in some cases oil heaters.
Gas is clean, easily available and presents no storage problems where there is a main supply.
The installation of any gas main in a house should always comply with the local gas board regulations.
Gas is not always available in rural areas and it can be costly to have mains installed into a dwelling. However, if you are in this situation but want to use gas, you can buy containers of Calor Gas.
All fuels can be used with a wet or dry system. Wet systems are more common. They work in the following way.
1. The boiler heats water.
2. The water is circulated by a pump or gravity.
3. The hot water is carried through pipes into heat emitters: steel panel radiators, fan or natural convectors, or skirting-mounted convectors.
4. Pipework for single or two-pipe systems can be smallbore or microbore.
Smallbore means a minimum of 15mm diameter or upwards.
Microbore is 12mm diameter or below.
5. There are open and closed systems. Open systems are those fed with water from a cold water tank known as the feed and expansion (F & E) tank by atmospheric pressure.
Closed or sealed systems are those that have a pressurised unit installed which isolates it from atmospheric pressure. This also enables the system to work at higher temperatures which can reduce the size of pipework needed.
These can work in one of two ways.
1. They can use a direct source of heat such as gas or electric fires.
2. They can consist of a ducted system, where warmed air is circulated by a fan through sheet metal ducting. Ducted systems can operate on any type of fuel.
Full, partial or background central heating
Full central heating means that every room has an emitter installed and that the temperature you require is reached and maintained when the outside temperature is as low as —1°C. A controlled system can be obtained by zoning. Here zone valves are used to shut off parts of the house while the rest is still being heated.
Partial central heating means that some rooms have no emitters. This is not ideal Central heating and hot water
It is economical to add the heating of domestic hot water into the central heating system. This can be done with all fuels except coal fired central heating in summer. The hot water and the central heating can be controlled independently and you should choose a control system that allows you to switch and time the water heating separately from the radiators.