Central heating radiators Designer radiators Bathroom radiators

Central heating radiators Towel radiators Designer radiators Bathroom radiators Radiator covers

Bathroom radiators
Central heating radiators
Designer radiators
Towel radiators
Radiator covers







Central heating radiators

Radiators work by heating the air which flows past them. Warm air rises from the radiators and colder air in the room falls. This circulation develops a flow of air around the room sending warm air from the radiator and delivering cooler air back to be heated. So, for radiators to work well there must be adequate clearance around them so that air flow isn't restricted.  Now you know why radiators are mounted off the wall a little and above the floor.


Radiators, as the term is normally used, are simple heat exchangers which distribute the heat by natural air circulation (hot air rises, so the heated air next to the surface of a central heating radiator rises pulling cooler air up from the floor level). They are simple (very little can go wrong), easy to install and operate.


It is worth remembering that any room can have more than a single central heating radiator, with rooms greater than 6 metres (18 ft) in any one direction, it is worth considering distributing a number of radiators to minimise the thermal gradient within the room.


Normally the manufacturer's data sheet will quote the output for when there is a temperature difference of 56 C (100 F) between the water in the radiator and the air in the room. Where the temperature difference is not 56 C, the following correcting factors are necessary to determine the actual anticipated output from the radiator.


Different manufacturers will quote slightly different outputs for seemingly similar sized central heating radiators, so where possible always use the figures from the manufacturers data sheet.



Balancing central heating radiators


With a 'feed and return' central heating system, the radiators near to the boiler/pump would tend to be warmer than the radiators further away. To avoid this, the outlet of each radiator is fitted with a 'lockshield valve' (shown right) which needs to be adjusted when the system is first installed. The 'lockshield valve' is normally covered by a push on cover to hide the adjustment.

The intention is to even out the flow of water through each radiator so that with the system in its normal operating condition, the temperature drop across each radiator is about 20F (12C). Problems with setting up the system may be experienced if the outside temperature is above the design operating temperature - if the outside temperature is above the system design value, the heat dissipated by each radiator will be less than intended by the design, and the temperature drop across each radiator will be less than 20F. If balancing on a hot summers day, adjust to achieve a lower temperature difference.

Once the central heating radiators in a system have been balanced, the valves should not need to be adjusted again unless the pipework or radiators are changed. The easiest way for a diy'er to measure the temperature drop across the radiators is to use a pair of radiator thermometers, they can be purchased or better still hired or borrowed. These thermometers just clip onto the pipework and indicate the temperature of the pipe (which is, effectively, the temperature of the water flowing within it). Most professional plumbers do not use these thermometers, years of experience has enabled them to balance a system just using a hand to check the temperature differences.









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