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Cold rads

Postby Shaun14 » Sun Jan 30, 2011 2:29 pm

Hi there,
I wonder if you can help, having lots of problems with my rads not heating up, I replaced about 6 a year ago and have just had a towel rad fitted, I have no heat what so ever with towel rad but when old rad was there it worked fine, I'm now getting even more problems as each day goes by, I only have about half my rads working properly,
I have a header tank, pump and boiler system, when I replaced rads a year ago the water was dirty but replaced, added fernox and bleed system but still no good, could system need a power flush or is pump no good, I know that boiler is a bit under spec should be 18kw but is 14kw, builder watching there pennies again
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Simply Build It

Postby william63 » Mon Jan 31, 2011 8:52 pm

This is a coincidence or what,
My sister has had a new towel rad fitted(a week ago and now has 4 rads not heating at all, and the other 3 taking ages to get warm. warm might be optimistic.
So upon visiting, I checked for air locks in supply and return pipes (really one circuit but), then bleed rads there was no air/hydrogen), result exactly the same condition except the towel rail worked (valve sticking I think), but its gravity fed).

To cut a long story short, after the heating had been on for a number of hours,I felt the inlet/feed pipe at all rads they were hot ( hmm no flow through radiator?) I bled a radiator again but this time , bleeding it for 5 mins or so, result the rad got warmer/hotter,this was the same with all rads as I bled them they got hotter.

All radiator valves were checked previously for position and they were open( and I tapped the valves, just in case they were lazy) .

Upon observing this phenomenon it was obvious that the outlet/return pipe work must be severely but not fully blocked, and the partial blockage must be pump/boiler side of the nearest rad to the boiler/pump suction/inlet, because it effects all rads.
A couple of rads eventually got warm, just. So a partial blockage rather than completely blocked return pipe.

I Think this problem was caused by installing the towel rad, disturbed loosened corrosion within the existing pipework etc and its moved to a more critical position causing this blockage.
Advised that a "descaler/cleaner" like fernox is put in left for a week or so and see if that shifts it (I have used it in the past and it worked).
Then flush system of the cleaner, then refill incorporating fernox"inhibitor"

The main observation that led to the realisation of what was wrong, was ALL inlet pipes to rads were hot ,but rad was cold,(no flow allowed through rads because return/outlet is partially/largely blocked) I know the position of the blockage is pump suction/return side of the nearest radiator (return pipe/branch pipe) to the pump because all rads are affected.

The new circulating pump was turned up to position3 just to see (but its not a pressure pump, its only job is to move/circulate a liquid)!!

A power flush is a final resort but at any thing up to £600 is a final option
Hope this helps.
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