3rd Heat Exchanger in less than 3 years - Is this normal

[-RV-]

We bought a newly built house 3 years ago, and it was installed with a Powermax 155x combi system.

We've had numerous problems with it

• leak
  new pumps
  new heat exchangers

These were covered on the inital warranty - so I wasn't too bothered. Now, we have the same problem and it needs another new heat exchanger !

I'm led to believe its because we live in a very hard water area, but the boiler has a "factory" fitted electronic scale inhibitor and Baxi say it that it should be more than capable.

Everyone we've spoken to gives us a different answer :-

• Water filter
  Water softener
  Electronic scale inhibitor
  ..others

As far as I'm concerned the whole thing is faulty - should it really need all this attention for a new machine ?!

I would really appreciate any honest advice as how to continue. I would hope there is something I can do so I don't have to spend £250 a year replacing bits that shouldn't need it

 

[ollski]

put a combimate on the boiler supply, need the m,edia changing annualy but are the next best thing to a full on water softener.

 

[simond]

Firstly, I should qualify my advice by admitting that we have only seen older Powermax and IMI versions.

If you have got through a number of hot water heat exchangers in a short period of time there must be a reason. You have not told us what it was that failed the HE. In other words, was it the primary or secondary circuits.

Your comments about scale make me wonder if it is the secondary becoming restricted, if this is so you are either running industrial quantities of hot water through it, or the water is getting overheated. (Limescale is separated from water at temperatures in excess of 65C).

If it is the latter this could be due to a poor incoming flow rate and/or a faulty temperature sensor.

 

[Agile]

You have given your location as Wiltshire.

Much of Wiltshire is on chalk and that porous rock is a good source of ( hard ) water.

Most professionals would fit a scale reducer or water conditioner in your location.

In any case even so with a properly operating boiler scale deposition should not occur.

With more technical details its difficult for me to give you any definite advice.

Tony

 

[corgiman]

gawd I hate these things

We do alot of warrantee callws on them, they have a electric inline scale inhibiter which is, quite frnkly, pants

 

[-RV-]

I live in Salisbury and the water is known to be hard, but maybe this isn't the entire problem.

It was fitted when originally installed with an electric scale inhibitor.....

The failure with the HE was that it was completely caked up, so much so that the water would not flow through - I don't know if it was the primary or secondary circuit that failed.

The problem that we experience is that the hot water pressure in the taps reduces through time, as does the length of time we have hot water. When the boiler is fixed (new heat exchanger) everything is perfect.

Then, as times goes on the pressure reduces and the hot water becomes cold very quickly - If I want a shower the water will be cold before I'm finished....

We're not running lots of hot water through it, so maybe there is some issue with the temperature sensors as you have mentioned.

We have been looking at fitting a scale inhibitor - a decent one just after the incoming water main. I will also look into the combimate. Any other suggestions would be helpfull

 

[lor]

only a water softner will work in these conditions ,dont waste money on any other (one that u have to top up with salt).

 

[corgiman]

only a water softner will work in these conditions ,dont waste money on any other (one that u have to top up with salt).

absolutley true, but dont forget to bypass it for the boiler filling loop

hello lor long time no see

 

[ChrisR]

the boiler has a "factory" fitted electronic scale inhibitor and Baxi say it that it should be more than capable.

I'm quoting a prof who looked into these things, who came to the conclusion that there is no scientific test which has shown that they work.
Neither do the radio frequency ones.
There is some evidence that under certain circumstances (silicates in the water I think it was) some magnetic ones have a limited effect.
I'll see if I can find the site...

So it's a combi mate, or a water softener. Or get your boiler carefully looked at, to check temps.
And CLEAN (descale) the heat exchanger - it should be possible before it gets competely clogged. (Perhaps have two - use one while the other's sitting in a bucket of citric acid!)


Found it:
http://www.chem1.com/CQ/index.html

 

[Agile]

Assuming its the secondary ( mains water ) side of the HE as evidenced in the hot water FLOW reducing, then removing and cleaning it every few months is not really a big task!

Assuming that you can take simple precautions, eye protection and latex gloves then Hydrochloric acid ( HCl ) purchased as Spirits of Salt 32% HCl solution will be fine if diluted to 10% by adding the acid to water and then poured cold into the HE.

It will quickly dissolve the lime CaCO3 and produce CO2 and Calcium Chloride which is VERY soluble ( indeed deliquescent ).

Even so, lime deposition should not occur below 60 C and I would wonder if the boiler's temperature control system is operating correctly.

Tony Glazier

 

[ChrisR]

Sulphamic acid - the industry standard acid for the purpose, would be safer. It's sold as descaler DS-3 by Fernox. It's in crystal form, which is less nasty to have about the place than strong hydrochloric acid.

That works, as you might have guessed, by converting the calcium carbonate to soluble calcium sulphamate.

 

[Paul Barker]

There's some tips from Kim and Agi to save in My Documents.

Thanks guys.

 

[Agile]

Hydrochloric is stronger and much quicker and works at room temperature. Its too strong to use in boilers or heating systems. Its ideal for disolving lime from the DHW side of plate HEs when they have been removed from the boiler. You can also use it at about 5% and 30 C in c.i. HEs when disconnected from the rest of the system.

HCl is also ideal for removing lime scale from baths and toilets. Thats the main purpose its sold for in the hardware shops. You can apply it with a paintbrush at the full 32%.

Sulphamic acid is much milder, in fact it does little below 60 C. Its not very soluble and often difficult to get enough into a boiler. Its main use is to remove lime scale from the primary HE of a boiler in situ but the boiler has to be powered to heat it up to 70-80 C to make it start to dissolve the scale.

Tony

WARNING, ALWAYS WEAR EYE AND SKIN PROTECTION WHEN USING CHEMICALS!

 

[-RV-]

Great information, thanks guys...

Firstly, I think I'll clean the HE as you suggested... Although I'm not confident doing it myself - I know someone who will !!

And, as suggested there may well be something else wrong - maybe the temperature sensor, so I will get that checked.

I've lived in Salisbury for years, and never ever had this problem with a single house - nor anyone else I know and no-one has a softener installed either....

 

[ChrisR]

HCl is also ideal for removing lime scale from baths and toilets. Thats the main purpose its sold for in the hardware shops.

Toilets yes, baths no. It'll go through the chome plating on the waste!

Sulphamic acid is much milder, in fact it does little below 60 C.
In terms of its action on alkalis (bases) it's almost as strong as hydrochloric acid if you compare equivalent molar concentrations.
It isn't as nasty in terms of what else it'll attack.

Its not very soluble and often difficult to get enough into a boiler.
It's classed as Very Soluble! I haven't had a problem with that.
He isn't trying to get it into a boiler...

Its main use is to remove lime scale from the primary HE of a boiler.
As I said, it's widely used for limescale removal. You'll even find it, in diluted form, in supermarket descalers.
Must say I've found it to be pretty good.