Plumbed in plinth heaters cold

9 Jan 2021
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United Kingdom
Hi, I'm looking for some advice please. I have a plinth heater in the kitchen that is connected to the central heating system. I have taken the heater out and tested by pouring hot water into it and the fan kicks in, so I know that it is working. I have re connected to the central heating system and bled the heater until hot water is coming through. However, when I close the bleed valve the water is not running through as the return pipe stays cold and feed pipe therefore goes cold slowly. I have tried closing the other radiators to force the water through so I could re balance the system but still get no hot water coming through it.
Is there anything I am missing that i
should be doing?
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They are metal flexible pipes. I think the feed pipe must be fine as I can get hot water through the bleed valve. How can I check or understand lock the return pipe?
Is the matrix blocked ?

Has it ever worked. They need a good flow to work.
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I have removed it from the system and poured water into it and the fan kicked in, butits never worked since I have lived in this house which is about 6 years. We have a gravity fed system, so not much pressure I guess.
Assuming you can remove the radiator... does water flow out of the flow and return pipes when you open them into a bucket?
You could link the flow and return with a suitable pipe and see if it gets hot?
Do you know where the pipes are plumbed in to your system? Perhaps they are both on the flow side?
I alwats bin the flexi pipe supplied as they are very restrictive, and just pipe in 15mm plastic.

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