Radiator Question

[jonwm]

Bit of a strange one so thought I’d ask her before calling in the plumber!

Got 2 radiators downstairs that don’t seem to be heating up fully compared to the rest of the house, they are both quite new (less than 2 years old) 1 is manageable but the other is in a colder room so really noticeable.

So as you look at it the pipe on the right with a standard valve is feeding it hot water, pipe is hot to touch, radiator is warm to hot on the top but like warm at best halfway down, and below, pipework on the left has a trv and the pipe work is warm easily can hold it tight with no feeling of pain associated with holding hot pipe :-)

Don’t think it’s sludge as it’s quite new and system was cleaned out not that long ago, have 5 other radiators that are red hot to touch all over, all older than this one.

Any advise appreciated

[jonwm]

Thanks for all the replies.

I'm currently doing a live test as i'm typing, not had chance before now, so all upstairs rad's off apart from bathroom which is a non trv towel rail, so the inlet pipe with normal valve is red hot to the touch, exit pipe with Myson TRV on it is warm at best, do we think its the TRV?

I'd say the top of the rad is hotter than the other day in a much shorter time, but bottom is still just warm.

[jonwm]

Update 2,
Felt brave and unscrewed the top bit of the TRV, the pin seems free on the actual valve, so stuck the heating on again and hey presto the radiator is red hot and the return pipe is too.

So looks like it was the TRV at fault, now questions:

Will my system now be out of balance as i've had all the radiators upstairs off whilst running it? (just turned them back on)
Can i get a replacement top and leave the top of the TRV off for now?

Thanks