Cold rad on bottom but hot on top

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Bosnian
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Cold rad on bottom but hot on top

Post by Bosnian » Tue Jan 22, 2019 6:00 pm

Evening all. This has probably been discussed to death but I can’t seem to cure this problem. The water comes in the flow side the TRV red hot. The problem is that it doesn’t
fully heat the whole rad. Have tried bleeding it and got some air out but still joy. The water at the other end of the rad at the valve is still cold. Should I try to completely drain the rad out or just bleed again. The rad is a double 1200x600 stelrad on a pressurised system. All the rest of the rads
work no problem. Thanks for any advice
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Re: Cold rad on bottom but hot on top

Post by Bob225 » Tue Jan 22, 2019 6:11 pm

stuck valve - open the valve fully and give it a tap, it could be sludged up, Take the rad off and flush it with a hose, when was the system last treated and/or flushed, do you have a magna-clean ?

Are both valves on the bottom of the rad ?

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wine~o
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Re: Cold rad on bottom but hot on top

Post by wine~o » Tue Jan 22, 2019 6:55 pm

Sounds like a sludged up Rad, remove flush through, replace. As an aside are your TRV's Bi-directional ? (Is there an arrow on the TRV body ?)
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Re: Cold rad on bottom but hot on top

Post by someone-else » Tue Jan 22, 2019 7:31 pm

As said, your rad is full of sludge, it has to go somewhere, and you have now found it. Clean rad (Outside, not in the house) put it back refill add inhibitor.
Fret not, a forum is a collection of opinions. Above, are mine.

Which is correct? Metre or Meter? Click the link to find out more.

Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

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Re: Cold rad on bottom but hot on top

Post by Bosnian » Wed Jan 23, 2019 5:40 pm

Thanks for info. Will take off and flush through and see what come out.
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Re: Cold rad on bottom but hot on top

Post by someone-else » Wed Jan 23, 2019 6:47 pm

Turn it upside down and bang it with a rubber hammer as well. (You will be surprised what comes out)
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Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

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Re: Cold rad on bottom but hot on top

Post by arco_iris » Wed Jan 23, 2019 7:42 pm

How old / what make / can we see picture of the TRV? Old style Drayton TRVs have a habit of the pin sticking, and may have been fitted on the flow side, not necessarily with a bi-directional arrow on the valve body.

(((

If the trv head appears to be held on with a clip, like a jubilee clip but with a screw & nut, undo it, wiggle the head off the valve, grip the exposed pin with pliers, work it in and out a couple of times to free it. It only moves a small amount.

Other makes suffer similarly - undo the knurled ring that holds the head to the valve, do the same. I had this issue regularly at a previous property & it was nothing to do with sludge.

)))
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