Is it cheaper to leave Combi boiler on 24/7 or on timer

[julioarca]

Basically, is it cheaper to run a combi boiler (gas) on low setting over winter 24/7 or is it more economical to have it come on twice a day, morning and night.

Probably 2.5 hrs a morning

and 7-8 hours at night?

Thanks

[oilman]

It will ALWAYS be cheaper to run something that is switched OFF!!!! You do not get a peak demand charge, and physics in our universe means having something at a higher temperature than its surroundings will need more fuel to do it, and hence more money.

Anyone telling you otherwise doesn't live in this universe, but could have found a channel from another universe where physics works differently.

[kev25v6]

I always leave mone on low setting as this keeps the house at 21 degrees which is fine for me. The boiler only kicks in for a short time as the house is always warm where as if the house is cold and you give it full blast heat for those few hours i would guess that you would be spending more in the long run because the house will be constantly heating up then cooling down, meaning you have to have it turned up higher for longer to keep the same temp as a boiler set on low constantly. (Does that make sense?)

[big-all]

its always cheaper to run at a temperature when you need it

i recon you will use about 20 to 40 percent more energy keeping a constant temperature
if you allow the temperature to stay constant overnight you pay 100 percent to maintain that temperature
as the temp lowers the heat loss reduces
if you house is average by the time you have lost about 5 degrees in internal temp your 100 percent to maintain temp has reduced to perhaps 20 percent
so thats 6 hrs overnight no input then 40 mins before you get up to full heat and by 1hr full temperature in the room

the actual amount of saving depends on actual heat loss and efficiency of the heating system

[Bamber gaspipe]

julioarca wrote:

Basically, is it cheaper to run a combi boiler (gas) on low setting over winter 24/7 or is it more economical to have it come on twice a day, morning and night. Probably 2.5 hrs a morning and 7-8 hours at night? Thanks

Use it when you need it. Timer works. Discard all the other lectures.

[Slugbabydotcom]

The hotter something is the more it will lose its heat.

Your house is losing heat at its highest rate for about 10 hours a day. You are proposing to let it lose heat at the highest rate for 24 hours.

Its as ludicrous as leaving your car engine running so its warm when you next want to drive it.

[oilman]

kev25v6 wrote:

............. if the house is cold and you give it full blast heat for those few hours i would guess that you would be spending more in the long run

Your guess is wrong. Mine is not a guess.

Quote:

because the house will be constantly heating up then cooling down, meaning you have to have it turned up higher for longer to keep the same temp as a boiler set on low constantly.

If it heats to your normal temperature, then cools when you're not there, then heats up to your normal temperature, it's average will be less that if you have it high all the time.

Quote:

(Does that make sense?)

Well DOES it?

It's no good trying to explain to these people matters of fundamental physics, anymore than it is to get over to most people that Richard Branson with his veggie fuelled 747 is up to anything more than a publicity stunt.

1) Hotter things cost more to keep hot, (except the sun).
2) Bio-fuels will not be a substitute for oil, nor will they have any significant effect on "global warming", even if you accept that it is a man made effect in the first place.

[julioarca]

thanks guys, guess I understand now

[Agile]

kev25v6 wrote:

I always leave mine on low setting as this keeps the house at 21 degrees which is fine for me. )

If your low setting gives you 21 ° C then I hate to think what your high setting will give you!

Ever though about using a pullover and setting the house to 18 °C like the teachers and vickars do? Saves your gas bill and the ozone layer!

Tony

[oilman]

What's it got to do with the ozone layer?

[Kes]

If you asked the nearest seven-year-old (before you get arrested) then they would probably say why don't you take a meter reading of your twice a day use, then take one of your all-day use, and take one from the other. I doubt if the seven-etc could spell initiative, though.

I don't have a meter as I don't have gas, but - being interested in any theory that might produce lower fuel bills - I took a few timings of my oil boiler this morning. With the c/h on it fires for just over two minutes in every five, approx 26 mins an hour. On the twice a day setting, allowing for the two 40-min warmups in the morning and evening, the boiler fires for 4.5 hours a day. As the boiler specs say 3.2 ltrs an hour that's 14 litres a day, just about what we use.

So if we left the boiler on all day it would not have the afternoon warmup, but seven hours of 26 mins during the day. The boiler would be on for a total of just over seven hours a day, using 22 ltrs. So twice a day it is.

We also have windows thrown open during the day, and wandering in and out, so I would be a real miserable git if the boiler were chugging away to warm fresh air.

Rgds.

[Alanka]

A house fully warmed up to the required temperature is like a bucket full of water with a hole in the bottom.

They both leak heat (water) at a rate that increases with temperature (water level). The higher the temperature (water level), the faster does the heat (water) pour out through the walls (hole).

Only when it is at outside temperature (empty) does the leaking cease.

To maintain a constant temperature (water level) you have to inject heat (water) at a rate that exactly matches the heat (water) loss, at any particular temperature (water level).

The higher the steady temperature (water level) required, the more heat (water) has to be injected per second.

If you need your house (bucket) up to temperature (full of water) first thing in the morning when you get up, should you keep the house (bucket) full of heat (water) all night?

Or should you switch off and let the heat (water) leak away overnight, and only inject heat (water) to raise the temperature (water level) to what you want just before you rise?

It's easy to see that you'll waste a lot more heat (water) keeping the house (bucket) full -- and the leaks going at full blast -- when you don't actually need to. And this waste will be worse the bigger the leaks.

Cheers,

Big Al

[[Davey]]

oilman wrote:

You do not get a peak demand charge

Alot of people go on about peak charges for power but.. But I'm pretty sure electric meters do not have clocks in them

[Diyisfun]

Alanka wrote:

A house fully warmed up to the required temperature is like a bucket full of water with a hole in the bottom. They both leak heat (water) at a rate that increases with temperature (water level). The higher the temperature (water level), the faster does the heat (water) pour out through the walls (hole). Big Al

Thats a good analogy

[mehran]

Good if you don’t want heat in your house we should be getting away from the simple on off controls to comfort and setback

You don’t want your house to plummet to -3 because there is a frost out side? Say 18-21 degrees for you comfort temp (when you’re up and about) and set back 14-16 degrees (for when you’re out or in bed)

Or you can have zones in your house. Take your bedrooms and living area as two different zones. Have the bedrooms have no (or little) heat during the day and at night have the living areas off.

Yes if you have it off you will not use any gas but then you have no heating.