Using a simple illustration from the motor car world, one can refer to the boiler as the engine of the central heating system. Subsequently, the radiators are the wheels that transfer the energy to the road, and helping the system deliver its potential. Radiators make a major difference to the effectiveness and performance of a domestic central heating system through their design, location and size. Quite often it is the boiler which is the focus when discussing your domestic heating needs. However, the heat that is generated by the boiler has to pass through the radiators to ensure it actually radiates out into the living space in the most effective way.
Radiators were first patented by a German engineer in 1855, which is hard to believe given some of the designs and shapes they come in these days. They are made of a hollow metal case, normally flat in shape and which is attached mostly to the wall of the room. Most UK radiators are made of sheet steel with attached fins to emit more heat. The heating medium, most frequently water, is pumped into the top of the radiator. The hot liquid emits the heat into the room and as it cools off it drops to the bottom of the radiator and eventually out. The air around the radiator heats up and creates a convection effect drawing in colder air to heat up.
UK made radiators are typically made of sheet steel with fins to emit more heat. The heating liquid, normally water, is pumped into the radiator. The hot liquid loses its heat into the room and as it cools off it drops to the bottom of the radiator and eventually is pumped out via the return valve. The air around the radiator heats up and consequently rises to the top of the room, drawing in cooler air. This convection effect keeps a circulation of heating within the room and constant heat within the home.
Despite their long life and history, radiators suffer from common problems such as air pockets. These pockets of gas are believed to be a result of two potential sources. One source is tiny bubbles that creep into the central heating loop through microscopic cracks in the piping (for example through holes in the brazing). A good installation and connection of piping should reduce the risk of such cracks.
Another common explanation for these air pockets it that they are the result of a chemical reaction that occurs when copper piping and other metals come in contact with very hot water. Such pockets (normally made of hydrogen) get trapped inside the system and find their way to the top most point of the system. This is why your radiator does not get hot at the top side, as it is filled up with air pockets rather than hot water. As this reduces the efficiency of the radiator and the central heating system as a whole it is recommended to bleed out such air pockets from the system. This can be easily done by using a bleeding key (which can be purchased in all major DIY stores in the UK). The bleeding key fits into a bleeding screw at the top of the radiator that lets the air pockets escape and return the system to good operating mode.
Radiators may suffer from another problem due to their chemical make. As hot water comes in contact with iron and other metals the reaction releases not only gases but also other chemical deposits which clog the system and reduce its performance. This problem is more acute with older systems and in extreme cases can make the central heating system completely in-effective.
Modern plumbers reduce the risk of such corrosion by adding a corrosion inhibitor to the mix of liquids within the central heating loop. In addition most plumbers these days power flush the system before filling it up to remove any such deposits and sludge. It is important to notice that power flush can remove debris even from brand new systems. Such debris can be a result of the metal workings and the manufacturing process of the radiator units or the copper piping.
About the Author:
Tal Potishman is editor of Heating Central, which publishes information about UK boilers, plumbers, unvented systems and solar thermal systems. He specializes in helping save costs and the planet by consulting on high-efficiency heating.
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