cold radiator

29 Apr 2004
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United Kingdom
Oil fired central heating system, pumped radiators, gravity hot water. A past boiler (solid fuel) required a "fuse" radiator to be connected across the gravity hot water system near the hot water cylinder in case the old solid fuel boiler overheated I suppose. That radiator is still there but since the new oil fired boiler was installed air appears to be collecting in that radiator only, although for the first year it was ok. I have taken the radiator out flushed it out and even replaced the valves no luck. Any ideas?
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If it was ok for the first year, you may find the whole system now needs cleaning.
You are probably correct in your reply, it's just that when I bleed that radiator there appears to be almost no pressure forcing the air out and I have checked the CH header tank and that is full. It is a small tank but there is still a couple of gallons of water sitting about six feet above the radiator. I should have mentioned originally that the hot water system is fine.
The same stuff which needs cleaning out is likely to be blocking the feed pipe, partially. Bring forward the date of the operation!
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So what's the procedure then? Drain out existing liquid (furnox and water mixture), fill up with fresh water and some descaling agent ( what's the best stuff?). Fire up and leave for a while (?) to descale pipes and rads. Drain out and fill up with fresh water and furnox or some other inhibiter. I would really be grateful for any info.
"best" is a day with a powerflushing machine and , er, experience. BUt , eg, find drain point and connect hose. Open loft hatch so you can hear when tank refils. Let som water out and listen to see how quickly it refils - will give an idea of what's going on.

You have an old system so anything vigorous would invite trouble with leaks. Use Fernox Heavy Duty (which it isn't) Restorer, leave it in for a week or three. Drain out completely, flush by refill & empty a couple of times. If it's all working put an inhibitor in.

If the feed pipe is blocked it will often clear if you get the mains connected tothe vent (Not trivial). The sludge in the feed pipe will hopefully get forced back up into the tank. Often there's a solid blockage where the feed pipe meets the system though (in your case quite likely to be at the lower cylinder primary pipe from the boiler) - which means cutting and rodding, or replacing pipe.
Thanks for the detailed info Chris. Apart from the draining and flushing with gunge remover it sounds a bit iffy, I know my limitations. I'll have a go at that and if it doesn't work I'll "Get the man in!" Thanks for the response anyway.

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