Radiator panel temperature difference ????

[Mutley56]

I would be grateful for your opinion on the following matter of radiator heat in a domestic central heating system.

Should all radiators feel the same temperature at the top and bottom of each one, and in between of course, no matter what its TRV is set at? The top feels hotter than the bottom. The feed inlet pipe to the radiator in question is too hot to hold for more than 1 or 2 seconds whilst the return pipe can be held comfortable for much longer.

I think that I have noticed the difference since topping up the insulation in the eaves attic overhead to the room that has the CH system’s room thermostat installed. Since then, the room stat has not called for the boiler to fire up so much which is understandable.

The central heating system was installed 2 years ago and comprises 11 radiators heated by a Worcester Bosch 24i gas condensing boiler. The boiler has been serviced annually from new.

Thank you for your advice.

Mutley56

 

[stem]

No they will vary. Heat emitted into the room by the radiator, is lost from the hot water as it travels through it. The water then goes back to the boiler for reheating. Because hot water rises and cooler water sinks to the bottom, the bottom of radiators is normally cooler.

As the TRV's start to close down because the set temperature is reached, the water flow through the radiator slows accordingly, less hot water enters and takes longer to travel through the radiator, so it will be even cooler as it leaves.

When the TRV's are fully open, the difference will be less, although the return pipe from larger radiators often is cooler as more heat will have been lost from the water than by smaller radiators.

Because of hot water rising, when a radiator goes off completely, it can stay hot at the top for sometime, whilst it can be cold at the bottom.

Also as TRV's in some radiators open and close that will also affect the flow to the others.

This assumes that the system is not blocked with sludge and is properly balanced to start with. Check out the FAQ's for method and how to balance radiators according to the temperature differential across the flow and return pipes. For FAQ click here

 

[Mutley56]

Thanks a lot for your considered reply stem.

In fact it is the largest radiator in the house that I am referring to. It think it is 120cm wide.

I will look at balancing the CH system again as there is a great deal about it on this forum.

Thanks again.

Mutley56

 

[MJN]

When the TRV's are fully open, the difference will be less, although the return pipe from larger radiators often is cooler as more heat will have been lost from the water than by smaller radiators.

Only in an unbalanced system, or where there is insufficient flow to the larger radiators (which amounts to the same thing).

Mathew