Radiator woes

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Hi all, I'm looking for some advice after a week of pulling my hair out with my radiators. Bit of background, un-vented system in a 3 story house with 12 radiators. Boiler on ground floor, pump on 2nd floor (changed 2 years ago). 2 Radiators in kitchen never get hot under normal circumstances and have never done since we have lived here. I've tried to balance in the past but have never had success. However, radiators in kitchen do get hot if turn off every other one at TRV and lockshield which would suggest a balancing issue? Maybe?

I've tried to work out which radiators heat up first and it seems to be 1 on the 2nd floor followed by 1 on 1st floor followed by 1 on ground floor followed by another then on 2nd floor and so on. So the loop seems to follow an up and down system 3 times rather than floor by floor with the kitchen always the last, does this seem plausible? Radiator in Hall which would be 3rd in sequence is red hot and only a couple of feet from kitchen.

Got a plumber coming next week but would be great if I can sort it in the mean time. Kitchen is 15 degrees at most in winter so unusable without heating. Please nudge me if you need any more info.
 
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1. Is the kitchen an extension, with radiators tee'd into the existing system. If so, pipework may be restricted.
2. When you say you have never had success balancing, do you mean the two troublesome radiators have never got warm, or that you have been unable to achieve the required temperature drop across all or some other radiators?
 
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Kitchen is original kitchen and original radiators. House only 10 years old. Balancing the rest of the house is fine but success has never found its way to the final two radiators which I assume are the last two on the loop. Inlet flow temp is max 40-42 and return temp half of that. However if I valve off all the other radiators they do get much warmer, almost tolerable.

Boiler temp set at 75 and hottest radiators see a flow temp of 60-63 and a return of 45-48. Towel rails always red hot regardless of trv and lockshield position.
 
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Yeah I did consider that, does get fairly hot when I shut all others down. Copper pipes from the little I can see but the rest is all concealed behind units and wall. I have another little radiator a few feet away in a toilet just outside kitchen and that is red hot and assume the next one up on the loop as last to get hot and one of the lowest flow temps but still in the mid 50s. It's strange it suddenly drops from 55 to 42 over a couple of feet.
 
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Close down the lockshields of all the hottest rads / towel rails until they are virtually fully closed. Two kitchen rads lockhields to be fully open ,as well as their TRV's.
What's the result ?
 
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Ok so in the middle of trying that now. Flow temp on kitchen up to 50 and return 30 so that seems to have improved, but radiator still very lukewarm however. 2nd floor room temps rarely drop below 19/20 even in winter so could shut those off permanently I suppose if it would help.
 
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System isnt well balanced then. You can try throttling down the lockshields on more radiatiors ,not close them completely though. Bedrooms are typical places where lower temps are ok .
 
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Ok thank you. Maybe I'm being too hasty with how much I am opening and closing the lockshields and need much finer resolution, instead of using a quarter turn try an 1/8 or 1/12 if they allow that level of precision? It's really difficult to know which way the pipes run in this house and whether I have the correct order of radiators. Am I right in suggesting the hotter the flow pipe the closer to the pump? Or could that be a red herring?
 
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Don't spend too much time working out which radiators are nearer the boiler or further away. The pumped water will find the path of least resistance ,will follow a long straight pipe run much more readily than a shorter run with lots of bends/ restrictions.
Sometimes certain rads lockshields on the system need to be just a tiny bit open ,in order to create a resistance there ,so the water will seek out a path to rads elsewhere.
 
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Many thanks for the info. I will have a look at restricting some of the other lockshields tomorrow and report back my findings.
 
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Ok, looks like I'm making some progress, I've spent some time this morning restricting the lockshield valves on most radiators.

For the towel rails I've heavily restricted both valves which seems to have helped also. One kitchen radiator much warmer, the other one still luke warm.

Trouble is now the lockshield valves on most radiators are now only open by 1/8 of a turn and they are still quite hot. Won't be able to close them further without shutting them fully. I've still got some room to move on the kitchen ones however which are open about 1 turn.
 
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Two kitchen rads lockhields to be fully open ,as well as their TRV's.
 
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Ok I'll do that! The one trv seems a bit dodgy on the one as well, the pin isn't stuck on the valve but the pin inside the TRV bit is a bit sticky so I've removed it for now.
 
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Hi, quick update, all my lockshields are now virtually closed on every radiator except the 2 kitchen ones which are wide open and they are much hotter than they were. Not sure what this says of the state of my plumbing however. They're not red hot however but acceptable, not sure what else I could do to push them further apart from fully closing off some radiators which may indicate that the boiler or pump is undersized?
 

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