Heat Exchanger clean - a possibility?
- Thread starter alban
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Fernox DS40 (citric + malic acids), citric acid (foams more than DS40), Phosphoric acid (as in Kamco FX-2), and there's always Hydrochloric acid. (Works well in low concentration added to citric acid.) Kamco do an "inhibited" hydrochloric acid whose name I forget, which is easier on stainless steel and copper.
There are of course other chemicals but those are the only ones you're likely to get your mitts on.
Sentinel do a recently developed brew, Ferroquest, a which is not acidic. BG use it a lot in their super-quick powerflushes. Good for distributed gunge but I'm not convinced it does a lot to boiler scale.
I strongly advise you only use chemicals designed for the purpose and strictly in accordance with the manufacturer's instructions.
There are of course other chemicals but those are the only ones you're likely to get your mitts on.
Sentinel do a recently developed brew, Ferroquest, a which is not acidic. BG use it a lot in their super-quick powerflushes. Good for distributed gunge but I'm not convinced it does a lot to boiler scale.
I strongly advise you only use chemicals designed for the purpose and strictly in accordance with the manufacturer's instructions.
How much FX2 did you use?
The instructions says 2.5 litres for each 10 radiators!!! Its best left in for several hours with the system operating!
In any case its wrong for the problem I expect you have in the boiler. For this you need to treat the boiler on its own!
Tony Glazier
The instructions says 2.5 litres for each 10 radiators!!! Its best left in for several hours with the system operating!
In any case its wrong for the problem I expect you have in the boiler. For this you need to treat the boiler on its own!
Tony Glazier
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What? you actually used a Kamco powerflusher? I thought you were skint!
If you're worried about bypasses etc, why not just connect up directly to the boiler? do you have CH + HW primaries off the HE or just one lot?
If you're worried about bypasses etc, why not just connect up directly to the boiler? do you have CH + HW primaries off the HE or just one lot?
Much crossing of posts here.
I've poured Kamco's Scalebreaker FX neat into a h/e and it fizzed plenty but I don't know if it's as good as hydrochloric.
Netaheat has one pipe leaving the top left, and tappings in the rear at top left, and TWO bottom right. In a pumped system ony one of the lower conns would be used so you could use the other as a drain point - if you can get whatever's in there, out.
I've poured Kamco's Scalebreaker FX neat into a h/e and it fizzed plenty but I don't know if it's as good as hydrochloric.
Netaheat has one pipe leaving the top left, and tappings in the rear at top left, and TWO bottom right. In a pumped system ony one of the lower conns would be used so you could use the other as a drain point - if you can get whatever's in there, out.
What I would like is someone to explain where all this scale is coming from. Sludge I can understand but scale cannot happen if the system is sound.
For scale to form you need continuos fresh heated water for example a plate HE, another example would be the kettle if you filled it with hard water and left it simmering away for 10 years there would be no scale build.
For scale to form you need continuos fresh heated water for example a plate HE, another example would be the kettle if you filled it with hard water and left it simmering away for 10 years there would be no scale build.
Sentinel & co use the word "scale" to mean not just limescale but also the hard stuff which stcks to boilers and pipes. Its assumed to be compounds of Iron, Copper, Calcium from water - plus anything else available, including oxidants, like oxygen obviously but also eg chlorine.
The simplest of the lot is magnetite, a black form of rust. It forms hard lumps in secondary heat exchangers. Read recently of a system which had a fine strainer on the return, but the secondary h/e still blocked with the black stuff, so it must accumulate there for some reason.
The simplest of the lot is magnetite, a black form of rust. It forms hard lumps in secondary heat exchangers. Read recently of a system which had a fine strainer on the return, but the secondary h/e still blocked with the black stuff, so it must accumulate there for some reason.
I have used the word "scale" in its correct and original definition, to mean "lime scale" or more accurately calcium compounds.
To answer John, if a boiler like the Netaheat is operated with too little flow OR with no pump over run then the water "boils" on the inside of the heat exchanger, not total boiling but the formation of small bubbles of steam on the metal surface. As it does this it deposits calcium compounds from the water and it gets worse on the second and subsequent occasion.
The net result after 10 years is that the old Neta has a considerable amount of calcium compounds some of which have dropped of the surface to the bottom.
The solution is to chemically dissolve them in an acid and flush them away. Hydrochloric is perfect but can attack copper if at more than a small dilution. Next best thing is sulphamic acid ( DS3 ) at about 80*C.
I am talking about the ideal treatment by a professional taking all the precautions and NOT suggestions for DIY treatments.
This particular case is a serious one and really beyond DIY treatment. Most of the DIY chemicals are too weak to have much effect and as in this case have been left in for too short a time.
Tony Glazier
To answer John, if a boiler like the Netaheat is operated with too little flow OR with no pump over run then the water "boils" on the inside of the heat exchanger, not total boiling but the formation of small bubbles of steam on the metal surface. As it does this it deposits calcium compounds from the water and it gets worse on the second and subsequent occasion.
The net result after 10 years is that the old Neta has a considerable amount of calcium compounds some of which have dropped of the surface to the bottom.
The solution is to chemically dissolve them in an acid and flush them away. Hydrochloric is perfect but can attack copper if at more than a small dilution. Next best thing is sulphamic acid ( DS3 ) at about 80*C.
I am talking about the ideal treatment by a professional taking all the precautions and NOT suggestions for DIY treatments.
This particular case is a serious one and really beyond DIY treatment. Most of the DIY chemicals are too weak to have much effect and as in this case have been left in for too short a time.
Tony Glazier
Scale is the only term in general use for the flaky, non protective rust which forms inside cast iron heat boilers. It is after all "scaley" in the physical sense. Local boiling will occur quite happily under that. No calcium or other chemicals (except oxygen!) need to be present.
If there were any reasonably safe brew which dissolved rust but not iron, it would be pretty useful. Industrially chemicals which attack surfaces, and therefore any small rough bits and oxides ON the surface are used, but they are not available for use in uncontrolled environments. I know what some of them are, but I'm keeping shtoom in case enthusiatic amateurs are tempted. Unqualified folk proclaiming themselves "professional" are quite rightly protected from their own ignorance. A little knowledge...
The nearest we get are the solutions mentioned above. They do significantly attack some of the the undesirables, but I wouldn't expect a perfect result. Buy a new boiler!
If there were any reasonably safe brew which dissolved rust but not iron, it would be pretty useful. Industrially chemicals which attack surfaces, and therefore any small rough bits and oxides ON the surface are used, but they are not available for use in uncontrolled environments. I know what some of them are, but I'm keeping shtoom in case enthusiatic amateurs are tempted. Unqualified folk proclaiming themselves "professional" are quite rightly protected from their own ignorance. A little knowledge...
The nearest we get are the solutions mentioned above. They do significantly attack some of the the undesirables, but I wouldn't expect a perfect result. Buy a new boiler!
My experience, which includes inspecting the internal waterways of CI heat exchangers, is that the debris inside is either lime scale or in models which act as a collecting sump iron oxides brought to the HE from the radiators ( or in most cases a mixture of both ).
Lime scale will only form in the HE in any case because the higher surface temperatures there will cause deposition ( and later give rise to kettling ).
Chris will be able to explain why but the mild steel used for radiators is much more prone to oxidisation that the much harder cast iron used in heat exchangers.
As I explained above, the citric acid mixtures are very effective on iron oxides and sulphamic acid is fairly effective on lime scale.
I have never had any problem in treating any form of debris in a system although the grey complex calcium, iron carbonates are not very responsive to anything apart from hydrochloric acid which should not normally be used in central heating systems.
Tony Glazier
Lime scale will only form in the HE in any case because the higher surface temperatures there will cause deposition ( and later give rise to kettling ).
Chris will be able to explain why but the mild steel used for radiators is much more prone to oxidisation that the much harder cast iron used in heat exchangers.
As I explained above, the citric acid mixtures are very effective on iron oxides and sulphamic acid is fairly effective on lime scale.
I have never had any problem in treating any form of debris in a system although the grey complex calcium, iron carbonates are not very responsive to anything apart from hydrochloric acid which should not normally be used in central heating systems.
Tony Glazier
Agile said;
Interesting statement Agile, are you suggesting Neta's should have pump over run ? Surely that just re-oxygenates the water and compounds the problem, not to mention the cost of heating your loft up with the over run !
pump overun / the pump runs for a time after the burner switches off
pumping over is what you are thinking bj
pumping over is what you are thinking bj
Only the biggest Netaheat (16-22) had pump overrun. The 10-16 doesn't boil when it's new...-ish!
I've smashed a few CI h/e's apart and every one has been rusty I think. Cast Iron (lots of carbon/graphite) rusts a lot quicker than mild steel (almost pure iron) used for radiators. It just tends to be thicker so it matters less I think! I don't think flakes of rust DO get carried around heating systems very much - their density is a bit high. Customer with a Keston C55 (ie big pump)wouldn't let me flush but has got a filter - nothing gets collected though its a very old system, plenty black water from rads.
I've tried tipping some flaky rust into HCl and it certainly didn't all dissolve. Could be different oxides of course. We're told the stuff in rads etc is Magnetite (Fe3O4) but there are others - Fe203 etc, hydrated forms etc. Could look it up I suppose but...
I've smashed a few CI h/e's apart and every one has been rusty I think. Cast Iron (lots of carbon/graphite) rusts a lot quicker than mild steel (almost pure iron) used for radiators. It just tends to be thicker so it matters less I think! I don't think flakes of rust DO get carried around heating systems very much - their density is a bit high. Customer with a Keston C55 (ie big pump)wouldn't let me flush but has got a filter - nothing gets collected though its a very old system, plenty black water from rads.
I've tried tipping some flaky rust into HCl and it certainly didn't all dissolve. Could be different oxides of course. We're told the stuff in rads etc is Magnetite (Fe3O4) but there are others - Fe203 etc, hydrated forms etc. Could look it up I suppose but...
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