Some Warm rads that get hot after a couple of hours

[Chris77]

In my old house I had a combi boiler. I installed the whole central heating system and it always worked very well. All rads would get red hot within about 30-40 minutes. In my new house it is a conventional boiler warming 5 rads downstairs and 5 rads up. A couple downstairs especially, get warm after about 30 minutes but do not get as hot as the others untill a couple of hours plus. I wondered if they were perhaps near the end of the flow. My pump has three settings. It is on the medium one. I have flushed the system 3 times now with descaller/cleaner which helped but did not cure the problem. The boiler is shutting off each time the return pipe on boiler reaches the heat chosen on boiler heat control but although this pipe is red hot it is not on the return pipes on these couple of rads. How do I know if the pump is not working sufficiently and need a new one. What is the guide for the speeds on the pump or is it something completely different? All rads are getting hot at top and are fully bled. If I close all rads apart from one that is not getting hot hot it still takes a while to get hot but return pipe on boiler is very hot even on lowish settings! If I turn the pump up to full will that force water into header tank if too high or does it not work like that.

 

[dcawkwell]

Balance system required.

 

[Chris77]

How can it be balance system when I said if I close all rads but warm one it still does not get hot for some time!

 

[Nige F]

Good question - I`ll have to sleep on it .

 

[Armo74]

If you have a TRV on the rad and the flow pipe is getting hot remove the head and make sure the pin is operating properly. But it does sound like it could do with balancing.

 

[Terry7556]

instead of using chemicals to flush why not takt that rad off the wall, and take it to the nearest outside drain and give it a good wash with a hose through the outlets.

 

[Chris77]

I don't have trv on the rads downstairs, I did not fit this system so when I update I will take care of that but the take off wall and flush through I think is a good idea.