Gas on constantly or on and off...?

tomstickland

SuzieSue wrote: »

As you say, the house will lose heat if it is heated all day but that needs to be compared to the amount of extra heat needed to warm up a stone cold house.

That extra heat is needed because the house lost that throughout the day.
It will take even more over the day if the heating is keeping it warm all day.

I like my bath filling analogy.
Temperature is water level in a bath that leaks all of the time.

I say only turn the tap on when you need the bath filled up to level.

You say leave the tap dribbling all day, because then it'll take less water to top it up when you get in from work.


If you intend to be in during the day, then the house is not empty and, yes, it might suit you better to leave the heating on in that case.
If the building is being left empty, then less energy will be used if it is allowed to cool during the day and then heated back up before use. This follows from the simple thermodynamic laws governing heat flow from a hot item to a cold sink.

Bigun28

Interesting conundrum here and perhaps a spanner in the works. I’ve also read on these threads where people keep the heating on all the time, but turn the boiler control right down.

Now trying to understand the workings of the central heating, if you have a room thermostat controlling the temperature at say 19 degrees, when the temperature falls below this, it will ‘call’ to the boiler to ignite and heat the heating system back up until the room temperature sensed by the room thermostat is back up to 19 degrees, whereupon the boiler will ‘switch off’ the burners.

If your boiler control is set to high, this heating effect will occur quickly, meaning the burners are only on for a short while. If you boiler is set to low, it will take longer for the room temperature to be raised. In effect, with a low setting, the boiler will be on longer because it will take longer to heat the system with the lower setting, perhaps using as much gas as if the boiler were set to a higher setting.

Normally, people will use a high setting on the boiler (particularly in winter) because when the system is timed, it may only have a short while to heat up, especially when you are running both the hot water and central heating systems.

So am I right in thinking that with people keeping the heating on 24/7 through winter, there is perhaps little gain in having the heating system on with only a low setting on the boiler when compared to having a high setting?

SuzieSue

Cardew wrote: »

SuzieSue,

Without wanting to sound rude, you really shouldn't comment on things you clearly don't understand. All you are doing is giving very poor advice!

There is a right answer. It is an answer determined by the laws of physics.

This is from the Energy Saving Trust - A Government agency set up to advise us all.



Can you not understand that if you accept the principle that you wouldn't leave an unoccupied house with the heating on 24/7 at a constant temperature if you were away for a year, then the same principle applies to a month, a week, a day, an hour!

Yes and that is the point, the EST is set up to advise us all which is why it has to generalise. For most people, their advice is correct but not for everyone. Your example of leaving an unoccupied house with heating on 24/7 for a year does not make sense - a house is heated for the benefit of the occupants, not for the benefit of the house. If a house is unoccupied you only need to keep it heated sufficiently to stop the pipes freezing.

Are you really saying that if someone is at home 23 hours a day and goes out for an hour each day that they should switch the heating off for that hour? Unless they leave all their windows and doors open or their house is so badly insulated that all the hot air escapes in that hour, it would not make sense to cool the house down for an hour only to heat it up again. As your quote from the EST says,Boilers use more power initially to heat water from cold, if they didn't then your argument would be correct and what is important is finding out how much that extra power usage is for your particular property and when the benefit of keeping the heating on constantly to reduce that inital power usage is outweighed by the cost of running the boiler constantly.

And that is my point - there are too many variables - what temperature people are confortable at, how many layers they are prepared to wear, if there are babies or elderly people in the house, how many rooms are occupied, how long the house is unoccupied for - so everyone needs to try it for a week or so and see what suits them. As I said, it works for me because of my particular circumstances.

Cardew

Randal wrote: »

So am I right in thinking that with people keeping the heating on 24/7 through winter, there is perhaps little gain in having the heating system on with only a low setting on the boiler when compared to having a high setting?

There is no easy answer to this I am afraid.

It depends on your boiler/system characteristics to a certain extent.

With older boilers they generally(not always) were more efficient and the higher water temperatures - as high as 82C - However the length of hot water pipe run is a factor to be considered - the hotter the water, the greater the losses.

With modern condensing boilers, the return water temperature to the boiler affects its efficiency and needs to be kept lower than with a conventional boiler.

Cardew

SuzieSue wrote: »

Yes and that is the point, the EST is set up to advise us all which is why it has to generalise. For most people, their advice is correct but not for everyone. Your example of leaving an unoccupied house with heating on 24/7 for a year does not make sense - a house is heated for the benefit of the occupants, not for the benefit of the house. If a house is unoccupied you only need to keep it heated sufficiently to stop the pipes freezing.

Are you really saying that if someone is at home 23 hours a day and goes out for an hour each day that they should switch the heating off for that hour? Unless they leave all their windows and doors open or their house is so badly insulated that all the hot air escapes in that hour, it would not make sense to cool the house down for an hour only to heat it up again. As your quote from the EST says,Boilers use more power initially to heat water from cold, if they didn't then your argument would be correct and what is important is finding out how much that extra power usage is for your particular property and when the benefit of keeping the heating on constantly to reduce that inital power usage is outweighed by the cost of running the boiler constantly.

And that is my point - there are too many variables - what temperature people are confortable at, how many layers they are prepared to wear, if there are babies or elderly people in the house, how many rooms are occupied, how long the house is unoccupied for - so everyone needs to try it for a week or so and see what suits them. As I said, it works for me because of my particular circumstances.

The EST don't generalise - they are quite specific! Read the quote.

The laws of Physics are not optional, and your house ain't an exception! Study the laws

The laws of themodynamics state that heat transfer is greater when the difference in temperature is greater. So house at 20C will lose more heat than house at 15C and in turn that will lose more heat than house at 14.9C etc. That applies regardless of the standard of insulation how many clothes you have on etc.

The OP asked a simple question - and the answer is that timed is cheaper. The longer the boiler is off - the less it costs!

aelitaman

Well to add some empiracal results to this discussion I did the measurements on my GCH to compare timed useage and on 24/7

When I fire up my boiler it uses 2.6m^3 of gas in the first hour of operation 0.6m^3 the next hour and then 0.3m^3 of gas for every hour after the firt two.

So with heating on from 6 till 8am in the morning = 2.6 + .6 = 3.2 m^3
Heating 5pm till 10pm = 2.6 + .6 + .3 + .3 +.3 = 4.1 m^3

So total gas used = 7.3 m^3

Whereas if I left it on 24/7 it wuld be 24 x .3 = 7.2m^3

So there are variables if I had it on 1 hour less in the morning and the evening then it would be more efficient timed than 24/7. Also my boiler is in the coalshed so it does not heat my kitchen with the waste heat it just keeps the local cats happy who curl up next to the outside wall (so heat must be lost in the coalshed eventhough there is no radiator in there).

I can only conclude that having boiler outside is very ineffcient in turns of its operation as the heatloss from this source is more than the heat loss of a well insulated home. Perhaps I should get the coal shed insulated.

I would be interested in other posters measuring thier gas boiler consumption from cold through to ticking over so that other calculations could be made.

SuzieSue

Cardew wrote: »

The EST don't generalise - they are quite specific! Read the quote.

The laws of Physics are not optional, and your house ain't an exception! Study the laws

The laws of themodynamics state that heat transfer is greater when the difference in temperature is greater. So house at 20C will lose more heat than house at 15C and in turn that will lose more heat than house at 14.9C etc. That applies regardless of the standard of insulation how many clothes you have on etc.

The OP asked a simple question - and the answer is that timed is cheaper. The longer the boiler is off - the less it costs!

Well, if you know so much about physics, I am very surprised that you can't see that there will be a point when the benefit of keeping the heating on constantly to reduce the inital power usage is outweighed by the cost of running the boiler constantly and until that point is reached, it makes sense to keep the boiler on rather than switching it off. That point depends on how well insualated your house it.

SuzieSue

aelitaman wrote: »

Well to add some empiracal results to this discussion I did the measurements on my GCH to compare timed useage and on 24/7

When I fire up my boiler it uses 2.6m^3 of gas in the first hour of operation 0.6m^3 the next hour and then 0.3m^3 of gas for every hour after the firt two.

So with heating on from 6 till 8am in the morning = 2.6 + .6 = 3.2 m^3
Heating 5pm till 10pm = 2.6 + .6 + .3 + .3 +.3 = 4.1 m^3

So total gas used = 7.3 m^3

Whereas if I left it on 24/7 it wuld be 24 x .3 = 7.2m^3

So there are variables if I had it on 1 hour less in the morning and the evening then it would be more efficient timed than 24/7. Also my boiler is in the coalshed so it does not heat my kitchen with the waste heat it just keeps the local cats happy who curl up next to the outside wall (so heat must be lost in the coalshed eventhough there is no radiator in there).

I can only conclude that having boiler outside is very ineffcient in turns of its operation as the heatloss from this source is more than the heat loss of a well insulated home. Perhaps I should get the coal shed insulated.

I would be interested in other posters measuring thier gas boiler consumption from cold through to ticking over so that other calculations could be made.

Thank you for backing up my point - everyone's personal circumstances are different and so there is no hard and fast rule.

SuzieSue

closed wrote: »

There is a hard and fast rule, but you are choosing to ignore it. 24/7 is more expensive, circumstances don't matter.

More expensive than what? More expensive than keeping the heating on for 23 hours while the house is occupied and then turning it off for an hour while it is unoccupied? I don;t think so, if you do then it is you who is ignoring the obvious,

Cardew

closed wrote: »

There is a hard and fast rule, but you are choosing to ignore it. 24/7 is more expensive, circumstances don't matter.

There is simply no point in re-stating the obvious.

The Nobel prize for physics awaits proof that the laws of physics generations of scientists have relied upon for years were wrong all along.

Seems like it might have been won;)