I have been told I need to replace the secondary heat exchanger on my Potterton Combi 80 due to limescale stopping the HW from remaining hot (CH is fine)
As the boiler is approx 5-6 years old, would money be better spent on a new condensing boiler?
Is there no way of removing the limescale rather than purchasing a brand new exchanger?
neil
I cleaned up a friend's one a few months back. It was quite easy. That was a Baxi 80, IIRC. The instructions will tell you how to remove and replace the heat exchanger. Watch that when you release the pressure, the water doesn't spew out over anything important such as the circuit boards, gas valve, etc. Buy a tub of Furnox DS-3, dissolve some in warm water, and keep pouring through the heat exchanger until it stops fizzing. You will likely need to mix up fresh solution several times (each time it goes blue, IIRC). Try to avoid getting any undissolved crystals of DS-3 into the exchanger, and flush it out well afterwards.
Flush out the other side too with a strong water jet -- it can fill with black crud which floats around in older heating systems (particularly if you didn't have enough inhibitor at some time).
Thanks Andrew.
When you say it was quite easy to clean, do you mean for a Corgi registered person?
I had a quote of =A3520 to have it replaced (=A3200 for the parts, the rest labour). The engineer mentioned that another alternative would be to connect a special pump to the cold and hot inlets that pumps Furnox through the whole system.
Can anyone recommend any of these pumps or whether they work?
Can I get the same effect from any of the other limscale removers I have seen on the Internet that use magents/radio/etc?
Regards Neil
Andrew Gabriel wrote:
No, I mean for me. I have installed heating systems, but I'm not CORGI, and I didn't install this one. The difficult part will be getting it out of the boiler. If you aren't familiar with such plumbing, then you might not want to tackle something like that as a first job. Cleaning it once it's out is easy.
Sounds like a power flush, except in your case, the blockage is probably on the hot water side rather than the closed loop side, so it won't work. If you are DIY'ing it and your time is therefore not accounted for, then it's better to spend the effort cleaning the plate exchanger. For a CORGI, maybe they don't bother and just fit a new one, since if they spend the time cleaning it and then find it's knackered, there's both paying for the time to clean it and cost of a new one.
Certainly not once it's blocked, even if you do believe in the magical abilities of a couple of flashing LED's to soften the water.
Thanks again.
Apparently the reason for replacing a part rather than cleaning it was down to the legality of having to dispose of the chemicals afterwards in the right way.
I just looked at the pipes the chap said to cut and place the pump on - the mains water inlet and the HW outlet. Would that still have no effect as you mention above?
To be honest I'm desperate to perform what you did and remove the part but I admit my plumbing is basic. Is it a case of 'unscrew this, remove part, unclip that' etc. or were there situations where specialist knowledge/tools or experience is needed? The engineer mentioned the tricky bit is normally putting the heat exchanger back in.
Neil
The plumber was telling you a lie. The chemical is eactly the same as you use to descale your kettle, and you do the same with it when you've finished.
Oh, that might work, but I never heard of anyone cleaning a plate exchanger that way. Anyway, you should really clean both sides. The other side won't be scaled up, but it might well have debris from the heating system in it which can be washed out. Oh, and what was he suggesting you should do with the cleaning chemicals afterwards? ;-)
I suspect your plumber doesn't know what he's doing or is just plain dishonest, but it would be interesting to see if any of the plumbers/heating engineers in this newsgroup think this is a standard way to clean a plate exchanger.
Look at the boiler servicing instructions. It will tell you how to remove and replace the plate exchanger (secondary heat exchanger). IIRC, it is held in by just 2 or 4 screws, and there are no additional plumbing connections (if I'm thinking of the right boiler). The tricky part is that it's behind the gas valve which makes access harder (I was also replacing the gas valve, so I had the valve out at that point and just protected the exposed gas pipes from getting water in them). Also, make sure you release the heating system pressure, or ~5 litres of water will spray out from the pressure vessel all over the electrics when you unscrew the plate exchanger -- it should say this in the servicing manual.
However, I don't want to push you into doing something you are uncomfortable tackling, and I would suggest you find another heating engineer.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.