Expected life of the Brawa mixing valve?

I moved into my property in June 2007 and thanks to this very helpful forum I identified and replaced the Brawa mixing valve (XC007) in April 2009. All was well until tonight (12th Jan 2012) when again water went cold after a burst of hot water. I removed the mixing valve and it has gone brittle and broken inside (Not as bad as the first one I replaced). I have ordered another one but now wondering is this normal for these valves to give up every 2 and a half years?

Thanks

Depends on the usage.
Also check the unit temperature. As heat transfers.
Mike
MGC/H2O
Norfolk

Thanks for your reply Mike!

Would not say usage is high, two bedroom house with two adults, roughly one bath and shower a day. The unit does get very hot as it is positioned close to the tank, do I need to adjust something?

Regards
Denzel

Have you had a de scale?
Check the unit temperature.
But if the unit was over heating, it would go up the vent into the header tank.
May be just bad luck.
Mike
MGC/H2O
Norfolk

Since I've moved in no de scale, though haven't noticed any degradation of hot water pressure or temperature (except for mixer valve probs)
Check the unit temperature? I'm no expert so not sure how? but no overflow to the header tank.
And I agree it is probably bad luck.

I will look into getting a de scale and a drain and refill over the next few months, as the unit was installed in 1997 my guess is it may have never been done! Is it worth doing or should I be leaving it alone and start saving for a new system. I'm in Harlow so a bit of a trek for you and your expertise to do the work, but if you are nearby one day how much would the above cost to do?

Many thanks again!

I use a temp probe around £10 to £15.
The reason I mentioned de scale was;
Some will do it via the washing machine taps.
This is not correct as the mixer valve would / could be damaged.
I would say you were unlucky that is all.
A de scale only applies if the DHW starts off hot then runs cold.
Leave it for say 15 to 20 mins and again runs hot say 5 litres then go cold.
This means the coil inside the unit is scaled.
And the unit has to heat the scale up before the water inside the coil.
When I de scale a unit. The mixer comes off. A modified valve goes on, then the de scale is carried out.
Flush out and refit mixer valve. If not known when valve has been changed recommend new valve at the same time.
And hence FITTED free!
If your unit is ok and working, showing no leaks etc. Hard call whether to change it.
Gledhill makes the Boilermate BP unit which may go in subject to space etc.
But a lot of work!
Mike
MGC/H2O
Norfolk

Many thanks again Mike for taking the time to reply, much appreciated!

Okay then I think the unit does not needs a de scale yet as normally it runs perfectly! No leaks from tank, but was actually thinking of changing to a different system altogether ie condensing boiler etc. I find this system uses a lot of electricity to keep the tank hot even in summer when it seems a bit of a waste!

Mixing valve is waiting for me to collect, I will fit tomorrow and fingers crossed it lasts a bit longer!

One last question then I shall leave you in peace, How does one actually adjust the temperature in the store tank?

Regards
Denzel

P.S Never mind, just found the setting on the thermostat, still has the factory seal on it. Might turn it down just a fraction!