Combi boiler: descaling secondary heat exchanger...

Hi, My Brittony "Combi 80" combination boiler's secondary heat exchanger seems slightly blocked (presumably with calcium and iron oxide). So I want to remove it and try descaling it. What is a good chemical to use, that's easy to obtain? And can anyone offer any other tips on unblocking these things successfully?
Many thanks,
Dave
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Citric acid?
Christian.
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On Mon, 20 Sep 2004 11:09:11 +0100, "Christian McArdle"

Are you serious? I can imagine that dissolving the limescale but what about the iron oxide? Someone suggested using a central heating system flushing liquid. If that's a better idea, can anyone recommend a good-value one that's easily available?
Cheers, Dave
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Personally, I wouldn't use anything that isn't suitable for potable water applications on the DHW side. Iron oxide can usually be flushed out with clean high pressure water, if you've got access to the component.
However, a properly maintained system shouldn't have any, whilst limescale on the DHW side will be quite common on any system in hard water areas unless a water softener or phosphate doser was used.
Christian.
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On Mon, 20 Sep 2004 16:25:47 +0100, "Christian McArdle"

Christian, Thank for the added input. If you were serious about citric acid, does that mean that lemon juice would do the job? Would that be better than the commercial bottled chemical you can buy for descaling kettles etc? Any tiips on how to apply the citric acid/lemon juice or how long to soak it or whatever?
Dave
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You can use white vinegar if you're looking for something in the supermarket, although it would take longer.
I'd say 15 minutes for citric acid or 45 minutes for vinegar, but follow the manufacturer's recommendations if you can find them.
Christian.
P.S. Kettle descaler is often (but not always) citric acid. Descalers for non-potable applications are usually based on more poisonous acids.
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On Mon, 20 Sep 2004 16:25:47 +0100, Christian McArdle wrote:

On the odd accasion I have needed to do this. I simply remove the DHW unit and fill it with dilute HCl. About 5 minutes seems enough.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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snipped-for-privacy@aol.com (Dave) wrote in message wrote:

There is a machine for this. I had to have a heat exchanger descaled, a few years back, and took it down to my local plumbers merchant who hooked it up to device that pumped a solution through it. What the solution was i don't know. The machine was portable and avaliable for hire so it is possible to descale the heat exchanger in situ. Try a few phone calls round to a couple of plumbers merchants, and or hire shops. BTW it cost me 15 quid to have it descaled - 7 yrs ago. If you want to run a pump through the whole central heating system you can hire the kamco power flushing system. They also supply the chemicals.
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Fernox sell descaler
Hydrochloric or phosphoric acid are the base of most descaling fluids
The problem is that you have to pump the stuff around to maintain the strength of the acid
--
geoff

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