Single radiator not heating up as much as others..

27 Jan 2014
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United Kingdom
Hi folks just a newbie to the forum so be gentle. I have checked the forums and cannot see anything similar. It’s the old chestnut of a single radiator not heating up as much as the others. I have 12 radiators in our home and 11 of them blast out heat but one only gets about 50% warm compared to the others. all are brand new and fitted with Danfoss RAS-C2 TRV’s.

Due to an error by the fitter this was the only radiator that the TRV was not replaced on, saying that it was a newish TRV (i.e. not an old part) I’m not sure whether the TRV is working properly (though the pin appears free and can move up and down) The pipe going into the radiator before the TRV is roasting as is the section of radiator after the TRV. It’s as if the water isn’t going anywhere, the pipe going aware from the rad is warmish but not roasting. Tried the usual freeing the pin, tapping the side of the valve lightly with a hammer to see if there is any sticking. Any advice would be appreciated. I’m not entirely sure how a small pin on the TRV can actually control the valve to open or close as there does not appear to be much travel in the pin. I wonder if you can remove the nut on top of the TRV that the pin sits in, but not sure if this would provide any further clarification of the problem.. Thanks in advance.. JD
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Bleeding or balancing are the likely issues. Both are addressed in the FAQ's on this forum.
Try turning off all other rads and see if it heats up.
As suggested maybe a balancing issue.
Was the system balanced when the new rads and TRVs were installed?

My guess is that it wasn't.
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No it wasn't balanced AFAIK ie no one went around adjusting radiators, just all valves open.. I'll check out the faq and see what I can glean from that. Doesn't appear to be air in the rad as water comes out when you open the bleed nipples (one on each panel). Thanks..
Thanks D appreciated... I'll check this out. I closed all rads except the one in question and it did get hot a lot hotter than normal.. but when I opened the others again the temp dropped..I can't help thinking it could be a faulty valve..but I don't want to drain the whole system to replace one TRV.. anyway it's a bug*er to refill...thanks again..

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