More faults have been added to the thermostatic radiator valve and radiator fault finding pages in the heating section. There are many reasons why one or more radiators in a house are too cold or too hot, use the information on this page 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. 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.