Radiators are the panels that fill with hot water to convect heat into your home.
Old style radiators had a single or double panel of various heights and widths, the bigger the surface area the more heat emitted. These days all panel radiators are convector radiators which include a row of fins welded to the back of the panel to increase this surface area and therefore emit more heat without taking up any more space.
There are three main types of convector radiator:
Single panel convector radiators which have one panel and one set of fins on the back of the panel.
Double panel convector radiators have two panels and one set of fins between the panels.
Double panel double convector radiators have two panels but also two sets of fins between the panels.
A column radiator typically contain steel or iron tubes. The hot water flows around the tubes heating the columns and the space between them. A column radiator is genrally a more efficient heater because they have a larger surface area than panel radiators which means they give off more heat.
Column radiators are ideal for large spaces and tall ceilings. They can be vertical or horizontal.
Most rooms only require one or two radiators but larger rooms may require more.
Radiator heat output is measured in BTUs (British Thermal Units). This is the amount of energy needed to heat a single pound of water by 1°F. 1 BTU is equivalent to 1055 joules and so the higher the BTU output the hotter the radiator will be.
To work out how many radiators you would need you need to find out the BTU of your room. To accurately calculate this you require you would need to employ a qualified heating engineer but it is possible to estimate this by finding the cubic volume of your room (height x width x length) - if your rooms are unusually shaped, separate them into rectangles and then add them together to get the values - and then multiplying it by the following average values:
You would also need to consider the desired temperate you want your rooms to achieve, whether your rooms are well insulated and also the amount of heat lost within the room via doors and windows.
You can find many BTU calculators online to make this calculation easier.
As air gets trapped in the central heating system it leads to cold spots or areas in your radiators where the water can't fill. In order to release this trapped air you use a small bleeding key to turn a valve located at the top of the radiator. Bleeding your radiators regularly can prevent this from building up and improve the performance of your heating system.
How to video?
This is a more extensive job to clean out the radiator system and get rid of any junk or sludge that has built up and must be done by a professional.