Combi Hot Water

Helen28

I have a Worcester combi boiler with an internal tank that I can use to pre heat the hot water.
I never have it on.
Does that mean that not using the pre heat function all the water in that tank has to be used first before I get hot water?
Seems a waste of water if I don't use the pre heat function

neilmcl

Well you likely "waste" some water whilst you wait for it to come up to temperature anyway. I'd rather that than constantly having the boiler come on pre-heating water I may or may not use. TBH, it's not a huge amount of water anyway.

ComicGeek

If it's a modern combi then the internal tank would likely be very well insulated, and therefore the energy wasted whilst stored is extremely small. If you have the model details, then you'll be able to find the exact figure from the manufacturer and then make more of an informed decision.

Personally I would use the pre heat function, as I know that I would use it at some point that day - different if I was away for a while.

neilmcl

ComicGeek said:

If it's a modern combi then the internal tank would likely be very well insulated, and therefore the energy wasted whilst stored is extremely small. If you have the model details, then you'll be able to find the exact figure from the manufacturer and then make more of an informed decision.

Personally I would use the pre heat function, as I know that I would use it at some point that day - different if I was away for a while.

Those small internal tanks in combis are never that well insulated, if they have them at all.. I've a WB Greenstar combi and tried the function for a little while when I first got it and the boiler was firing up throughout the day and night, complete waste of energy all for not having to wait a minute or two till the water comes up to temp. It's been on eco ever since.

ComicGeek

neilmcl said:

ComicGeek said:

If it's a modern combi then the internal tank would likely be very well insulated, and therefore the energy wasted whilst stored is extremely small. If you have the model details, then you'll be able to find the exact figure from the manufacturer and then make more of an informed decision.

Personally I would use the pre heat function, as I know that I would use it at some point that day - different if I was away for a while.

Those small internal tanks in combis are never that well insulated, if they have them at all.. I've a WB Greenstar combi and tried the function for a little while when I first got it and the boiler was firing up throughout the day and night, complete waste of energy all for not having to wait a minute or two till the water comes up to temp. It's been on eco ever since.

It varies a lot between models so just needs to be checked on the manufacturers data sheets. You need the information to make an informed decision. Some even used to use an electric immersion to preheat the tank...

Helen28

It is a Greenstar CDi Classic 29CDi

southcoastrgi

You misunderstand what it does, your boiler doesn't have any kind of internal tank or stored hot water, the preheat just keeps the plate heat exchanger up to temperature at all times so tbh unless you use lots of very short amounts of hot water it's a complete waste of gas, yes it will take slightly longer to get hot water but I doubt you will notice too much