10minute delay in firing up CH & HW

[HexagonalBob]

Hi
I've got a Keston, sealed system for HW & CH. It all works quite well but recently (over the last year) it swtiches on . . pump runs . . lights come on . . thermostats go on demand etc but the boiler refuses to spin up & ignite. It usually takes (exactly) 10 minutes before it will start.
I've bled the system (rads/pump etc) but no joy. It varies . . some days it works OK but on others I'm lying in bed at 0600 and hear the system switch on, pump runs etc but no boiler . . until 10 mins later . . I hear the impeller spin up and the system ignite.
I know, I could just reset all the timings to -10minutes but I thought some bright spark may know why it does this and hopefully have a solution.
Cheers
Mikey

 

[sturharv]

Some model boilers have a pre-set delay, are you sure its not meant to do this.... why is it a problem, set everything to come on 10 mins earlier

 

[sturharv]

Having read it properly... he he. I suspect it could be something to do with the controls / room stat / programmer, sometimes they have a delay on them.. not sure why.

There may be either an outdoor sensor or frost stat confusing things.

 

[mikej2005]

With the Worcester Bosch 'Optimiser' timer stats, you set it to come on 1 hour before the time you would like your house to be your ideal temperature and it learns how late it can come on to achieve this, therefore (theoretically) saving money.

ie. if you want the house to be 19oC at 7am, you set the timer to come on 1 hour earlier (6am) and it'll leave it as late as possible to ensure that the house gets to 19oC in time for 7am.

Could your's be along similar lines ?

 

[HexagonalBob]

No, it's not meant to do this.
There's no extra stats.
I suspect some air in the system.
Just curious to know why it took exactly 10 mins to "come alive"
It only does this from complete cold, so I suspect the air is bubbling up to the pump/boiler, which is at the highest point . . I know bad design but I've inherited it and each year I change sommit.
I hate the boiler - it's noisy! It's on the wall halfway up the stairs (naff place) which means everyone can hear it.
Are there whisper-quiet condensing boilers?
Thanks for replies!
Mikey

 

[sturharv]

I don't think it would be 'exactly 10 mins' if it was air in the system, this would be much more random?

Most new boilers are pretty quiet now.