Radiator temperature difference?

Hi, Top needs to be hot and not cold, as air in the radiator can cause a cold spot. The top will always be hotter than the bottom as heat rises and causes expansion, the main temperature difference is measured at the boiler, as long as you should be getting around a 11 to 15 degree differential from the flow pipe of the boiler to the return pipe, then all the radiators should work fine. If they are all measuring around the same then they are all working the same. Depending on the heating temperature setting on the boiler itself, if its set at its maximum level then the radiators should measure around 65 to 75 degrees Celsius at the top. Radiators with large cold spots in the shape similar to a hill or mound inside at the bottom of the radiator represent a blockage more often than not. If there is around a ten degree difference that is common. more may be able to be done to improve the temperature difference between the top and the bottom but this would need further investigation.

The radiator should be the same temperature top and bottom

There should be a recommended 12°c loss between flow and return on a radiator.