Combi Please explain

[Diyisfun]

I thought one of the advantages of having a combi, was that you got instant hot water.
I have a Worcester Greenstar 440, which I dont know why pre heats a small volume of water. Its controlled by an inbuilt timer, I can only get hot water if the timer is set to be on.
I assume this is how it is designed but why?

 

[dcawkwell]

It is designed to work that way so that you can switch the hot water
off during the night and therefore stop the boiler firing during the night
wasting gas.
You can also switch the preheat feature off by selecting the eco mode.

So just switch the hot water to constant and select the eco mode
and the boiler will only fire when hot water is demanded.
It might take it a little longer to get hot to the tap but will be
lighter on the gas.

 

[Diyisfun]

Thanks for that..
Im now trying to turn the underfloor heating off. Think I will make a new post on that.

 

[ChrisR]

I can only get hot water if the timer is set to be on.

Isn't it only the "keeping hot" bit which is timed? Read the book!
I'd expect you would get HW at night, but you'd just have to wait a moment for it to get het up.

 

[Diyisfun]

Chris, I read the book, waiting for the film.lol
Its not very clear as to how it works.
Last night no hot water, the timer was off, I expect hyot water on demand 24 hrs a day.
Im new to all this, I had a convention system in previous home.