Practical Home Energy Saving
Updated: 19-Aug-2014
Central Heating Radiator

Radiator Faults

Central Heating Radiator with TRV

There are many reasons why one or more radiators in a house are too cold or too hot, use the information here to identify the areas for investigation .Please read through all the possible diagnosis before jumping to conclusions. Always check the simple reasons first before looking for expert assistance, often the cause is simply due to thermostatic radiator valves (TRVs) being turned off or incorrectly set.

The information here makes the fundamental assumption that the system did work properly at some stage, if not then you are into investigating the design which is beyond the scope of this page. Whenever radiators are not working properly the heating system is not running at maximum efficiency which means there are opportunities to cut heating costs.

Heating systems are sometimes zoned to enable different parts of the house to be heated to different temperatures e.g. split between upstairs and downstairs. Where this is done there are zone control valves to manage the water flow depending on the room temperatures or time switch settings. in this case there is likely to be a room thermostat and/or time switch setting for each zone.

If the rooms are reaching the desired temperature and the thermostatic valves are cutting off the flow it is likely that all the radiators will be at different temperatures. It all depends on how hard the radiator is working to maintain the temperature. The hotter the temperature the less the thermostatic valve is closing. How hard a radiator works depends on the size of room being heated, the size of the radiator, how high the thermostatic valve is set, how well insulated the room is and how often any external doors are opened and closed.

Generally downstairs radiators will be cooler as the rooms are insulated by any heated rooms above. If there is a very large difference and no other factors that affect this it may be worth looking at whether the loft insulation can be improved to reduce heat loss through the ceilings and cavity wall insulation to reduce heat loss through the walls.

It is worth noting that radiators are likely to be slightly hotter at the top than the bottom, how much will vary from system to system, room to room, the design of the radiator and the airflow around it. As long as the difference is no worse than the drop across the radiator this is not an indication of a problem. Before jumping to the conclusion there is a fault make sure the system has fully stabilised first.

Firstly establish whether the problem affects one radiator or several to help narrow down the choices. We have tried to put the faults in each section in order of how likely they are to be the cause.

One Radiator Is Cold

One Radiator Is Too Hot

One Radiator Doesn't Get Hot Enough

One Radiator Is Cold At the Top

One Radiator Is Cold At The Bottom

One Radiator Only Is Hot

All Radiators Are Cold

Several Radiators are Cold

Downstairs Radiators Are Cold, Upstairs Radiators Are Hot

Downstairs Radiators Are Hot, Upstairs Radiators Are Cold

Radiators Furthest From The Boiler Are Cold

All Radiators Don't Get Hot Enough

All Radiators Are Cold

Some Radiators Are Warm When Water Heating Only Is In Use

Noises From One Or Several Radiators

One Or More Radiators Need Bleeding Regularly

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