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Circulation problem!

View the thread, titled "Circulation problem!" which is posted in UK Plumbers Forums on UK Plumbers Forums.

billski

Gas Engineer
Can any one tell me what the fault would be with the pipe work?
The boiler is a Worcester combi, hot water works fine but heating is not working correctly. Only one radiator gets properly hot ( 4 rads in total ) and the others gets slightly warm over a period of time. The flow pipe is red hot from the boiler, but the return doesn't even get warm. Eventually the boiler over heats and turns off. Cycles away and starts again once cool. If the one radiator that gets hot is turned off the flow goes no where and boiler over heats instantly. New pump fitted in boiler and diverter valve working as it should. It's as if the water is heating one rad and going round in a loop, so not returning back to the boiler, then when the water gets too hot in the loop it over heats the boiler and turns off.
New radiators have been fitted recently, so the pipe work must have been altered in the floor and walls, but what could have been piped in wrong pipe wise to cause it? Specially as turning the one rad off that gets hot to stops everything..
 
1. Look at the balancing of the radiators. If they all have TRVs, open all the lock shield valves fully (noting their original position). If not all TRVs, look up radiator balancing. (System probably needs to be balanced anyway).
2. Check that flow and return have not been connected by pipe anywhere.
3. If any of the new radiators were designer column type, check they have been connected correctly. Many of these must have flow into and return out of specific points.
 
In addition make sure the pump is actually working. Report back please and I am sure others will help out
Rob Foster aka centralheatking
 
In addition make sure the pump is actually working. Report back please and I am sure others will help out
Rob Foster aka centralheatking
Morning mate. He cannot take the case of a Worcester combi. The case forms Part of the sealed appliance. @billski how do you know the pump and diverter is working? Did your engineer check it or you?
 
There is only 4 rads in the system, 3 with TRVS 1 with lockshields. Pump is brand new and working as is DHW working. Yes 3 are colomn rads and 1 is a towel rail. I know column rads have an in and an out, but I've seen them fitted before incorrectly and yes they do work but just not very well. And it can't be the TRVS as the towel rail will not work on its own. As I said turn the one rad off that works and the boilers boils, leave it on and it will run for a good 20mins until the boiler gets too hot and turns off. To me it has to be pipped in wrong. Perhaps the flow is going through the one rad, but I can't get it in my head how the pipe work could be wrong for it to make its own loop and never return back to the boiler, as the return pipe never gets hot!
 
Guessing the blanks were removed when the rads were piped up. Daft I know but ..................
 
Guessing the blanks were removed when the rads were piped up. Daft I know but ...

The one rad gets red hot, can't be that, and another gets luke warm near the one that gets hot.

The pipe work has been worked on in the summer ( not by me ) and it's all under the floor!
 
The one rad gets red hot, can't be that, and another gets luke warm near the one that gets hot.

The pipe work has been worked on in the summer ( not by me ) and it's all under the floor!

Would I be right in my belief that if the flow and return to the non working rads is coming off the 15mm's of the the rad that is working, they (non working rads) wont pick up the heat as the hot water would just circulate round one rad???

Therefore the pipework needs to be checked, and definitely connected to the main 22mm flow and return pipes??
 
Well if any one is interested..the problem was in the new pipe work going to new rads fitted in the summer. Contractor got his plumbers back in and altered the pipe work. They had to take some of the new flooring up to sort it. Not sure what they did, but it's sorted.
 
Well if any one is interested..the problem was in the new pipe work going to new rads fitted in the summer. Contractor got his plumbers back in and altered the pipe work. They had to take some of the new flooring up to sort it. Not sure what they did, but it's sorted.
Thank you we all like reports back it helps and makes what we do a bit more fun
Rob Foster aka centralheatking
 

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