central healing boiler

[kate3]

My baxi combi boiler has recently started heating up the radiators when running the hot water or shower. At the weekend the bolier started making a really loud banging noise after the hot water had been running for a while and the system lost pressure.
I called an engineer out yesterday who said it was due to a limescale blockage and that the system needed flushing, is this right? If it is caused by a blockage the cost is not covered by my insurance, and when I questioned the engineer about how he knew it was defiantly limescale he said from experience.
How do I know whether the diverter valve is faulty or the heat exchange plate is scaled up? Please can anyone help!

 

[kevplumb]

sounds more like a dodgy diverter valve to me FWIW

 

[doitall]

Another BG post then.

Bet they want £700.00 for the pleasure.

 

[mickyg]

What happens when you just run the hot water? does it get hot and stay hot?

 

[kevplumb]

 

[mickyg]

Another BG post then.

Bet they want £700.00 for the pleasure.

I spoke to a mate the other day, and reckons they are pushing heavy on the sales now. They want them to sell £500 ugrades per month, 4 cods, 2 boiler sales leads and a magnaclean!

 

[kate3]

What happens when you just run the hot water? does it get hot and stay hot?

Yes hot water does get hot and stays hot, but after a few minutes boiler starts making really loud banging noise

 

[mickyg]

its possible he may be right to some extent although scale in the plate to plate wouldn't cause the rads to come on. Its possible you may have more than one fault. I was thinking a blocked plate to plate on the primary side, but the fact it gets hot and stays hot has thrown a bit of a wobbler in....
The most annoying thing is that it doesn't take long just to whip out the plate to plate to check and be 100%, and I suspect he just wanted to get out of the door, as is the case with alot of engineers working for insurance companies.

 

[bengasman]

Along the lines of what Mickey mentioned, scale/corrosion build up can be in primary heat exchanger or secundary, and is also known to stop diverters from moving freely, and kill pumps.

It is a very common problem, so the chap may well have been right. At the same time, possibly because it is has a good chance of being at least part of the problem, a number of bg engineers use it as a quick diagnosis.
That means they can tick the box: saleslead generated, which helps to reach their target, if it goes through, they also get a bonus, and he can be in and out in 5 minutes to race off to the next item in his overbooked diary.

As you will have to pay for it yourself anyway, you might as well get a local independent to check it. Maybe all you need is a chemical flush. Even if you do need a powerflush, an independent can do a fine job for half of what you have been quoted.