Boliermate iii - too hot

Apologies if I cannot expressed this technically but I have been having ongoing issues with a boilermate iii. We have cover with BG and over the past year had numerous jobs done on it to address the following issues:

1. the heating coming on when not times to do so
2. The top expansion tank overheating - it seems to be kettling.

We have had 2 divertor valve changes, ball valve, pumps, powerflushes, sensors, new pcb and several rewiring of the pcb with the problem seem to be getting worst. The thermistor on the boiler has also been replaced. The cold feed was redone 5 years ago. In the last 2 days we have discoved we have a leak from the expansion tank and the BG plan is to replace this next though I am concerned whether this will actually address the issue. I have had the system on this morning so I could have a quick wash and the water is of a very high temperature and a loud buzzing sound come from it.

Should not be a problem to fix your troubles.
But the leak will not fix the buzzing or the extra hot water!
Sounds as if you have had a fair bit done, so good you have cover!
Cold feed 5 years ago, I presume it was blocked?
Is the unit free of sludge?
Mike
MGC/H2O
Norwich
Norfolk

thanks for responding Mike.

I didn't think putting in a new header tank would resolve the too hot water problem - I feel BG are trying very hard to resolve our issue but seem to be stabbing in the dark and replacing/ rewiring stuff that may be ok.

Though the system was powerflushed on 16th March I am not 100% convinced it is sludge free especially since seeing one the pump replaced on Friday had lot of sediment present in it. When they drained the system there was a lot of dirt on Friday (20/4/12) and I was told it was just sludge had built at bottom of the tank again.We were advised to have the new cold feed put in when we moved here and transferred BG cover from old house as the old feed was blocked in 2007.

Liz31

Well I hope your BM III was not power flushed, as Gledhill does not recommend it!
The boiler and system yes BUT NOT THE BM III.
Things will not work properly if there is too much sludge present.
It would be advisable to put in a few litres of sludge remover ( 1 litre to every 100 litres)
Run it for a month and then drain the system.
And drain the unit too.
And if a house each and every ground floor rad.
And the boiler if on ground floor.
Time consuming, but I have had customers prepared to pay for the works, which are very worth while.
You will have to see what they propose. Give them a chance at least.
More so if you are on a plan with BG.
I think you would find if you let the plan lapse they would not be that keen on re starting it!
Mike
MGC/H2O
Norwich
Norfolk

Thank you for this advice. My intention is not to allow the BG contract lapse but I wanted to check out what I should be asking about. What they were doing re the powerflush on the 16th March seems a bit of a mystery to me but I will try to find out more. I was wondering whether they should be going the chemical route - we did add fernox cleaner f3 to the system at the end of Feb.

I will talk to them again tomorrow.

What ever you add must be at least 1 litre to every 100 litres.
So what ever your unit is (should be a label on there.
And the system as in rads and boiler etc.
Mike
MGC/H2O
Norwich
Norfolk