[nheather]

Is it better to leave the hot water part of the boiler on all the time or just have it switch on in the periods you expect to use it (obviously a little before to give it chance to heat).

At first glance it would seem a no-brainer but the more I think about it I'm not so sure.

My thinking is that if it is on 24hrs then the boiler should only run a little every now and then to keep the temperature up.

But if I just use it for periods - say morning and late afternoon\evening then the water in the tank has long periods of time to cool and will then need a lot of energy to heat it back up the next time the boiler comes on.

Obviously, if a large amount of water is drawn - bath\washing machine then a large amount of energy will be required to heat the cold water replacing it but that should be the same in either case.

Could be that the total energy required for each approach is about the same.

Anyone know the definitive answer or can point me at some ingo.

Cheers,

Nigel

[robh2002]

Originally Posted by nheather

Is it better to leave the hot water part of the boiler on all the time or just have it switch on in the periods you expect to use it (obviously a little before to give it chance to heat).

At first glance it would seem a no-brainer but the more I think about it I'm not so sure.

My thinking is that if it is on 24hrs then the boiler should only run a little every now and then to keep the temperature up.

But if I just use it for periods - say morning and late afternoon\evening then the water in the tank has long periods of time to cool and will then need a lot of energy to heat it back up the next time the boiler comes on.

Obviously, if a large amount of water is drawn - bath\washing machine then a large amount of energy will be required to heat the cold water replacing it but that should be the same in either case.

Could be that the total energy required for each approach is about the same.

Anyone know the definitive answer or can point me at some ingo.

Cheers,

Nigel

The answer is only heat the water when you need it.

The reason is that if you keep the hot water take full of piping hot water it means you maximise (and maintain) the temperature difference between it and the surroundings and therefore maximise heat loss. Same goes for central heating. Keeping the house hot all the time maximises the temperature differences between inside and out and maximises heat loss. Turning on when needed (or a bit before) and off at all other times makes a big difference.

This is one reason why a combi boiler is useful - you only heat the water you need, when you need it - so no time to allow it to cool.

Hope that's of some help.

[ad47uk]

Originally Posted by robhowell

The answer is only heat the water when you need it.

The reason is that if you keep the hot water take full of piping hot water it means you maximise (and maintain) the temperature difference between it and the surroundings and therefore maximise heat loss. Same goes for central heating. Keeping the house hot all the time maximises the temperature differences between inside and out and maximises heat loss. Turning on when needed (or a bit before) and off at all other times makes a big difference.

This is one reason why a combi boiler is useful - you only heat the water you need, when you need it - so no time to allow it to cool.

Hope that's of some help.

I like my combi boiler, the only problem is that the water runs slow and it takes ages to run a bath.

[robh2002]

Originally Posted by ad47uk

I like my combi boiler, the only problem is that the water runs slow and it takes ages to run a bath.

True. Even a 30kW boiler can't produce much more than 0.17L/s...we need to wash in something with a lower heat capacity!

[ad47uk]

Originally Posted by robhowell

True. Even a 30kW boiler can't produce much more than 0.17L/s...we need to wash in something with a lower heat capacity!

You mean like the river?

[robh2002]

Originally Posted by ad47uk

You mean like the river?

I meant something other that water - but a washing in a river would certainly cut down the bills!

[Tim Cooper]

Originally Posted by ad47uk

I like my combi boiler, the only problem is that the water runs slow and it takes ages to run a bath.

My 2 year old condensing combi still pumping out hot water too hot to handle with the tap full on ( & i have really good water pressure) my old Saunier Duvall was a piece of crap in comparison I think you'll be amazed how far the "Combi" has come on.
Tim.

[cheekymonkeyme]

Only heat the water as you need it, I have fallen foul to huge bills because of having it on constantly in the past though i have a combi boiler now and it has hot water on demand and is cheaper