Power flush in many cases a waste of time and money since B.G started this fad every one jumps on the band wagon if your syst. is that bad spend your hard earned on replacing the 20 or 30 year old rads. Could never see the logic in power flushing with a new boiler in situ.And correct me if wrong double rads dont flush propperly ,I was always taught to take individual rads off and flush independently.I tend to to treat chemiccally before installing and flush, then cleanse and flush, install add inhibitor and never have problems.But then 5/6 hundred quid is easy mopney for 4/5 hours work and when the loose bits cause problems 3/4months later can honestly say it was power flushed
What Combi do you recommend?
- Thread starter Whippet
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I keep noticing the "silicon" being implied as important in aluminium - silicon heat exchangers. Some folk seem to think this is new technology - it isn't. I've read that the heat exchangers are "coated" with silicon, which appears to be completely untrue.
Silicon is added to aluminum castings to make them harder and cast better - the flow is better at lower temperatures. Some other physical properties are improved too, eg the thermal expansion is reduced, but I don't think those are significant.
I haven't found much about the effect of Si on corrosion resistance in Al castings. Basically it isn't added to affect that, and I wouldn't be surprised if it makes Al slightly more prone to corrosion by some chemicals. Silicon doesn't form any sort of oxide on the surface of aluminium either. (As for example chromium does on stainless steel). Thinking of condensate, mild acids generally, don't attack aluminium; its oxide protection is highly protective.
So unless someone can enlighten, there appeas to be no "silicon" issue.
I daresay we're going to see dramatic pictures of Al alloy heat exchangers turned to grey mush, and the alloy blamed. It IS a reactive metal. If you fix a sheet of aluminium, outside, with brass screws, the aluminium may have all gone from around the screws in a year or two. That's an electrolytic effect, of course, and one to be worried about.
The worst thing you could do would be to use a lot of aggressive flux, which would introduce chlorides, and then not flush, then not use an inhibitor. (This would also apply to stainless steels - to which chlorides are very aggressive). Strong alkalis will also kipper Al alloys quickly.
Porous castings, parts with high or cyclic stresses, or sublect to erosion by particulates in high flow areas, could all present problems.
Al/Si alloys have been around long enough, surely, for responsible manufacturers to NOT have problems, as long as responsible installers do their bit. But I don't think comment is needed on the responsibility of manufacturers or installers.
Has anyone actually seen much evidence of short life for Al alloy heat exchangers? I haven't, yet, but these remain weak, reactive alloys, which won't be as forgiving as some of the materials we're used to.
Silicon is added to aluminum castings to make them harder and cast better - the flow is better at lower temperatures. Some other physical properties are improved too, eg the thermal expansion is reduced, but I don't think those are significant.
I haven't found much about the effect of Si on corrosion resistance in Al castings. Basically it isn't added to affect that, and I wouldn't be surprised if it makes Al slightly more prone to corrosion by some chemicals. Silicon doesn't form any sort of oxide on the surface of aluminium either. (As for example chromium does on stainless steel). Thinking of condensate, mild acids generally, don't attack aluminium; its oxide protection is highly protective.
So unless someone can enlighten, there appeas to be no "silicon" issue.
I daresay we're going to see dramatic pictures of Al alloy heat exchangers turned to grey mush, and the alloy blamed. It IS a reactive metal. If you fix a sheet of aluminium, outside, with brass screws, the aluminium may have all gone from around the screws in a year or two. That's an electrolytic effect, of course, and one to be worried about.
The worst thing you could do would be to use a lot of aggressive flux, which would introduce chlorides, and then not flush, then not use an inhibitor. (This would also apply to stainless steels - to which chlorides are very aggressive). Strong alkalis will also kipper Al alloys quickly.
Porous castings, parts with high or cyclic stresses, or sublect to erosion by particulates in high flow areas, could all present problems.
Al/Si alloys have been around long enough, surely, for responsible manufacturers to NOT have problems, as long as responsible installers do their bit. But I don't think comment is needed on the responsibility of manufacturers or installers.
Has anyone actually seen much evidence of short life for Al alloy heat exchangers? I haven't, yet, but these remain weak, reactive alloys, which won't be as forgiving as some of the materials we're used to.
alumiminum heat exchanges do not rot they flake and breakdown which is the grey dust and goo you see in side the boilers[blocked condense traps] the silicon is added to the ali to help prevent this and prolong the lifespan of the exchanger the only way to avoid and prolong the ex life is use stainless steel but some people have a view that stainless is not so efficent in thermal transfer,ali/sil heat exchangers have been used in europe for years without too many incidents some i believe have been running upto twenty years.treatment of the water is a uk thing not common practice in europe.the sooner uk manufacturers offer reliable boilers with the bugs ironed out and quality components instead of using the public as test beds they may get less bad press from installers who are getting sick of their excuses for their lousy products.one manufacturer offering a 3/5 year warranty on their products only if it is serviced by them is not worth the paper it is written on because of the exclusions,does it cover the fan pcb pump diverter all things that if produced properly will last longer than that in a correctly installed boiler let the manufacturers offer proper goods with good warranties instead of blaming the installer,got to go have a sermon to preach
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gasgeezer said:
They don't build them to last that long now - surely? I heard somewhere that they only last 10 to 15 years.
Right gents, if I can interrupt (because I don't understand a word you are talking about!!!).
Opinions please on the Vaillant Turbo Max
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