Cold radiator

Rad1o · 17 Oct 2021

Now that the heating is going back on, one raditor does not want to play.
After the winter I usually leave all the TRVs on full open. When I switched the heating back on, ALL the raditors were warming up as mormal.
I then turn the TRVs to the position adequate for the rooms. After that one raditor downstairs even in the fully opened position is not warming up.

I bled it with the lock shield closed and open. I gently banged on the body. No luck so far. I guess the plunger part is stuck in the off position.
The TRV is a Drayton 4.

What other options have I got other than drain the complete system and take the TRV out?

terryplumb · 17 Oct 2021

Take the actuator head off the TRV ,and see if the pin in the middle of the valve body moves up and down when you press on it. If it is stuck down rad won't heat.

Rad1o · 27 Oct 2021

I had the radiator off after draining downstairs. The radiator, TRV and lockshield were clear. I then put X200 down both pipes - flow and return - and the return is very sluggish to drain. I filled the system again and there was heat in the radiator ONCE andthen again the next day is stayed cold again.

I will leave the X200 in the system for a couple of weeks and probably have to try something else. But what??

Can I connect a hose to the open pipes and "flush any muck out?

What is a good descaler if the x200 does not do anything?

terryplumb · 27 Oct 2021

X200 isn't any use for cleansing a central heating system,X400 is what you should use ,and that's not going to do much if it isn't circulating fully.
If you close all other radiators TRV,and leave both valves open on your problem radiator ,run central heating ,and see if it now heats up fully. Is your system sealed / pressurised ,and do you have a hot water cylinder ?

Rad1o · 27 Oct 2021

HW and CH come on separately and are controlled via a mid position valve. The system is pressuriyed with an expansion vessel.
I will run the system with the radiators shut off tomorrow.

Rad1o · 27 Oct 2021

Turning off most of the other radiators has worked to get some heat back into the bathroom radiator, although it is dead slow. I have opened up the others gently and still have some heat in there.

I put X200 into the system because it was advertised as system descaler which can be left in and does not require draining.

terryplumb · 27 Oct 2021

A descaler is completely different to a cleanser. Your pipes get clogged with sludge ( if indeed that is your issue),nowt to do with scaling.
Is the bathroom radiator a panel radiator or towel rail type ,and is it the only one that hasn't been heating up ?
Your system needs balancing ,and cleansing. As long as all radiators are heating up ( even though they may not heat uniformly) adding X400 will have a good chance of doing its job.

Rad1o · 27 Oct 2021

The bathroom rad is a spiral tube radiator. It has always been a very fast one. I know about the balancing of radiators and use it where two would be very different to warm up, like beginning of loop and end, not where one does not warm up at all.
I will get some x400 and add that as well.

Rad1o · 4 Nov 2021

Thanks for the explanation of X200 and X400, terryplumb.

X400 almost immediately did the trick.

terryplumb · 4 Nov 2021

Good . Have you got a magnetic filter on the system ?

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Cold radiator

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