Limescale problem

[tobydog]

When we had our extension built we took the opportunity to have all the Economy 7 removed and full central heating installed with a condensing combi boiler. The boiler is a Firebird C26 and we are already having problems with the heat exchanger even though the two year warranty hasn't even expired yet.

Firebird say it is down to limescale but our plumber said he would be surprised if it failed this early for that reason even though we are in a hard water area. Firebird asked if we have a limescale preventer fitted and I said we haven't but that we would. I still have to take this up with Firebird separately, however, yesterday we had an inline limescale preventer fitted. It's a Salamadar SESI electrolyte unit that has a copper outer and a zinc/magnesium anode. Our plumber fits these to all his boilers. He didn't actually fit ours.

Due to the awkward way in which the water main comes into the house, it would have meant re-working the pipes so the plumber fitted the unit directly to the boiler mainswater feed pipe. I don't have an issue with this, however, my curious nature got me Googling and I read that these units mustn't be fitted closer than 3m from the appliance but the plumber has fitted it less than a meter. Is this really a problem?.

I've not been billed yet but would appreciate some advice. Thanks

 

[MdB]

I would speak to the manufacturer of the limescale preventer and see what they say.

 

[Moo]

In our last house we installed a proper water softener (the sort that has to have a separate mains-fed drinking tap in the kitchen) and in over twelve years nothing got furred up with lime scale.

 

[tobydog]

Just as an update, the manufacturer (Salamader) sent me company literature which clearly stated that these in-line copper / zinc lime fighters are to be fitted with at least 3m of pipe between them and the appliance being protected. I aksed what would happen if they were positioned closer and their response was that there is no evidence that they would be less effective but 3m is preferred :? .

Our plumber said that he would relocate it but that he has had no known problems with fitting many others right next to all types of boilers. He has written to Salamander saying that they should be much clearer in the instructions provided in the product packaging.

It turned out to be the 'balance valve' (?) and not the heat exchanger that has failed. I now need to take this up with Firebird.

 

[LadyArowana]

. I aksed what would happen if they were positioned closer and their response was that there is no evidence that they would be less effective but 3m is preferred :? .

Which begs the question, why? Surely if you don't test something then you don't know whether it might actually be more effective, and if they had tasted and found it made no difference then their guidance seems spurious. I suppose we should be glad that they are in the water softner biz not the pharmaceutical one.

Good news that it is still in warranty, hope you get some satisfaction from the manufacturer.

 

[88v8]

Hope it is indeed not the heat exchanger. That could be expensive.

Modern boilers are extremely sensitive to limescale. Even a small thickness significantly impairs heat transfer and overheats the alloy heat exchanger. With the old cast-iron exchangers, this wasn't such a problem.

I would never rely on any sort of electronic scale preventer. Always use Fernox water treatment or the like. It is essential that the correct amount be added to the water in the system, from the time of first firing. This will prevent any initial deposit of lime forming.

What usually happens is, treatments such as Fernox being expensive, not enough or none is put in. Or it is not put in until the system has been run and confirmed free from leaks, by which time an initial flash of scale has already formed. As I said, 'from first firing'.

Or not enough treatment is put in because the plumber can't be bothered to work out the total water content of the system... boiler, header tank, rads, pipework... and so doesn't know how much should be put in anyway.

Or of course the system may be faulty, for instance a slow leak which is diluting the water treatment.

Do you ever have to bleed the rads? That would indicate a fault.

The gfch system I installed in our previous house was still working fine when we sold it. The boiler was 21 years old. It had Fernox in ab initio. The rads never needed bleeding.

I would check for leaks by tying up the ball valve in the header tank and checking every day to see of the level is falling. Once confirmed OK, I would do a full chemical descale, flush many times, then refill with the correct percentage of Fernox. After that, I would check the Fernox every year using their test strips. All very tedious.
Or you could just have an open fire.

Ivor

 

[tobydog]

Good news. It is the balance valve and Firebird are replacing it under warranty.

I have to say that, despite some rather negative press about Firebird boilers that I read post installing, their customer service has so far been spot on - 10/10. They are always very quick to respond and sorted the issues I have had. I know that they should given that this is a warranty matter but I'm sure many other firms would fall down. We didn't even chose the boiler as it was simply installed by the plumbing subcontractor as part of the overall extension prime contract.

Thanks for the info Ivor. I am seeing our plummer tomorrow to have the limescale device moved so I'll talk to him about flushing the system. We only had to bleed the radiators when the system was first fired up, however, the system has now settled down. We have a self bleed valve now but we still have to sort the towel rail in the bathroom every now and then. The problem is that doing it too much lowered the system pressure which meant I had to top it up. I was told that topping up with fresh water also brings in fresh air ( :? ) and it becomes a cycle.

I'm sure we did have an inhibiter in the system when we first started but we needed to have all the thermo rad valves replaced soon after (by the same plumber) but I don't know what went back in, if anything.

 

[88v8]

If you have to bleed the rads at all - and a 'self-bleed' counts as bleeding - it indicates that there is internal corrosion in the system. This could be from leaks leading to fresh make-up water bringing in air, as you say, or design error leading to 'pumping over' which aerates the water, or simply from insufficient inhibitor.
Eventually the pump will clog from sludge, the rads will rust through. If the bleed air smells of rotten eggs, that confirms corrosion is active. It's not air you're bleeding out, it's hydrogen sulphide which is a corrosion by-product.
As hydrogen is lighter than air, you can collect it in an inverted jam-jar. Keeping it upside down, put the lid on, then light a match, turn the jar the right side up and apply the match as you undo the lid. After the explosion, pick up the glass and resolve to use a tin can next time.

Every year I went round all the rads, checking the glands on the valves and seeing if bleeding was required - think it must have been ten years and more since I last had to bleed any rad.

Ivor