Over heating combi
- Thread starter bunser
- Start date
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Bunser. Has your boiler got a plate to plate heat exchanger? I think it has. In that case, I'd go for limescale incrustation within the plates. There will be poor exchange of heat (scale is an excellent insulator). It will require descaling. Where exactly in the country are you?
The normal range of pH values are between 1 and 14 with pure water at 7.0 in the middle.
Caustic soda solution would be about 14 so your alleged figure is much stronger than caustic soda solution! Better check your pipes!
More important DONT drink it if the pH value really is 14 !!! It will dissolve your tongue!
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I really wonder if you mean to say its a hardness of 17 parts per million ( or 17 mG per litre which is the same thing ).
Thats only starting to be moderately hard and in normal circumstances would not cause any problems.
Tony Glazier
MOD
see 10a
Caustic soda solution would be about 14 so your alleged figure is much stronger than caustic soda solution! Better check your pipes!
More important DONT drink it if the pH value really is 14 !!! It will dissolve your tongue!
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I really wonder if you mean to say its a hardness of 17 parts per million ( or 17 mG per litre which is the same thing ).
Thats only starting to be moderately hard and in normal circumstances would not cause any problems.
Tony Glazier
MOD
see 10a
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Bunser. If it's a plate to plate HE you don't see the limescale!!! Did you flush it with acid and observe if any CO2 bubbles came down the clear tubes of the flushing pump?
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..And the flow remains virtually the same as usual in most cases as the water just takes an easy route through plates not scaled-up.
MOD
see 10a
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..And the flow remains virtually the same as usual in most cases as the water just takes an easy route through plates not scaled-up.
MOD
see 10a
Scalgon said:
The definition of water hardness is based on the amount of calcium it contains per litre.
* Soft water contains less than 30mg of calcium per litre
* Moderately hard water contains between 30 and 60mg
* Hard water between 60 and 120mg and
* Very hard water contains more than 120mg of calcium per litre
That's the main heat exchanger, not the DHW (hot water) one. If this is quite an old boiler (RSF 24 GC no. 47 651 01), I think the DHW heat exchanger is the older white chamber sort, with internal copper tubes. Diverter valve is a 3 port motorised valve. Separate DHW flow switch.
I have not taken out the DHW exchanger. I probably will, so what would be the best thing to flush it through with?
Thanks
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Just had a listen to the boiler again while the hot water was running.
It sounds like the flow is speeding up then slowing down, is this normal?
Thanks
MOD
see 10a
Thanks
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Just had a listen to the boiler again while the hot water was running.
It sounds like the flow is speeding up then slowing down, is this normal?
Thanks
MOD
see 10a
Bunser. Chris may be right, you may have the old water to water (separate) HW heat exchanger - in which case (usually, though not always) the flow would be reduced if there are limescale deposits. Though I have seen VERY many times combis overheating because of a layer of limescale on these old type HEs. If you have a plate to plate then it would be about the size and shape of a brick, and stainless steel. Look in the parts section of the installation manual if you have it for verification of what type. Whichever you have, if you want to flush it then you must use a pump made for the purpose. Use sulphamic acid. It would help also if you told us where you live - say the county if you don't want to reveal the town. Limescale varies over the country but is really bad in places - like where we operate from, Reading! No other reason why we're here!
The varying noise could be the effect of the flames going up and down - noise is a bit like a kettle.
I recently descaled a secondary h/e (both sides) with "scaleaway", very hot, which worked fairy well. Hydrochloric acid is better, but awkward. Limescale is easy to shift, its the black stuff boiler side which is harder. You need to clear them both. Sometimes the pipes block too, so worth a check.
I recently descaled a secondary h/e (both sides) with "scaleaway", very hot, which worked fairy well. Hydrochloric acid is better, but awkward. Limescale is easy to shift, its the black stuff boiler side which is harder. You need to clear them both. Sometimes the pipes block too, so worth a check.
I enquired about another pump but they said its not made anymore and the new pumps have got bigger bsp fittings and that there is no reducer available. The pump is a WSP.
I can get hold of hydrochloric (35%) and perhaps give the HE a flush.
Thanks
I can get hold of hydrochloric (35%) and perhaps give the HE a flush.
Thanks
Standard CH pumps are 1 1/2" threads but you can get 3/4" upwards perfectly easily, though from boiler spares places not general plumbers.
Quite often you can just change the pump motor but it needs to be the same make or it won't seal. Is yours a Wilo? Old pumps do go slow quite often. If you run the poump with the motor off, it should be really hard to stop it with one finger. Any easier and it's probably dud. Look at the rpm and see if you can guess...
"Spririts of salts" is about 30% HCl, which is stronger than you need. Dilute it by adding acid to water never the other way round. Nasty stuff so wear eye and hand protection. Trousers would be a good idea too...
Quite often you can just change the pump motor but it needs to be the same make or it won't seal. Is yours a Wilo? Old pumps do go slow quite often. If you run the poump with the motor off, it should be really hard to stop it with one finger. Any easier and it's probably dud. Look at the rpm and see if you can guess...
"Spririts of salts" is about 30% HCl, which is stronger than you need. Dilute it by adding acid to water never the other way round. Nasty stuff so wear eye and hand protection. Trousers would be a good idea too...
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