How should one maintain the temperature in the house??

Idiophreak

Your point's well made, but it still relies on a rather theoretical notion that having your heating on thermostat will ensure a constant heat throughout the day, which for most central heating systems just isn't the case - they're binary systems, either on or off, so the temperature will actually wander between, say 17-19' for a specified temp of 18', in a peak-trough manner, as you see on a broader scale in the on-off model. This will certainly detract from the maths of your argument.

Anyway, you clearly know what you're talking about a lot more than I do, so I won't attempt to disagree any further - but you can easily find plenty of examples (many on this board) of people who reckon it's cheaper to leave it on...I'm not sure why they'd lie about it...what would be in it for them? It could well be, then, that it's a marginal difference and tbh if it's marginal, I'd rather have the house warm all the time than half the time...:)

Cardew

Idiophreak wrote: »

Your point's well made, but it still relies on a rather theoretical notion that having your heating on thermostat will ensure a constant heat throughout the day, which for most central heating systems just isn't the case - they're binary systems, either on or off, so the temperature will actually wander between, say 17-19' for a specified temp of 18', in a peak-trough manner, as you see on a broader scale in the on-off model. This will certainly detract from the maths of your argument.

Anyway, you clearly know what you're talking about a lot more than I do, so I won't attempt to disagree any further - but you can easily find plenty of examples (many on this board) of people who reckon it's cheaper to leave it on...I'm not sure why they'd lie about it...what would be in it for them? It could well be, then, that it's a marginal difference and tbh if it's marginal, I'd rather have the house warm all the time than half the time...:)

To return the compliment;) Your point about the tolerance of thermostats is well made. However far from detracting from the maths, it actually proves the point.
e.g. Widen the tolerance of the thermostat so it drops from the set 18C to, say 14C and you will save more money than if the heating came back on at, say 16C.

I have never implied that people are lying.

There are scores of post on MSE from people who are convinced that strapping a magnet to the fuel line of their car or oil central heating boiler will reduce consumption by 30%(one claimed it improved his love life - but thankfully didn't go into details!!)

Others on this very forum are absolutely convinced that the single act of switching off their TV at the wall at night has made a dramatic reduction of xx% on their annual electricity bill.

All of us are guilty of justifying something we want to have, and in many cases we want to believe that 24/7 heating is just as economical.

Me - I am absolutely convinced a Ferrari 430 will be a sound investment - my wife aint!! This despite the fact that I have 'proved' to her that other exotic cars have been an excellent buy.

mech_2

red_flump wrote: »

The Canadians have done this:

http://irc.nrc-cnrc.gc.ca/pubs/fulltext/nrcc48361/nrcc48361.pdf
http://www.cmhc-schl.gc.ca/odpub/pdf/63816.pdf

Two identical test houses built next to each other to the latest insulation standards.
One house thermostat set to 22C
The other they tried 22C day 18C 23:00-06:00 night setback
also 18C day 09:00-16:00 and night setback
and 16C day and night setback

Biggest savings found with the 16C night and day setback up to 21%

However with these highly insulated houses designed to cope with -20C nights the savings with an outdoor temperature above 4C was minimal. The R-2000 standard for house insulation is I think better than our current buiding regs.

Conclusion
The experiments showed that thermostat setback has significant
potential as an effective and inexpensive energy-saving method,
even in an energy-efficient house.

Red

Very interesting, thankyou. Just the kind of thing I have been looking for for ages. The problem I have with it is that it's far too different from a typical UK dwelling size/construction/heating system/climate. What would the savings be for a 1930s brick-built 100 sq m semi-detached house in suburban Britain? We still don't know.

Though having said that, 13% was the same kind of savings figure I came up with experimenting my own house last winter. Sheer coincidence I suspect, as all the variables were different.

Mazio_2

The other factor with central heating is the water temp inside the boiler can (I believe) switch the burner on even if the rads or room thermostat dont require it because there is an internal thermostat operating to keep the water temp circulating around the system (the numbers 1-6 normally on the controll in your boiler).
So when switched on 24/7 this will also play a factor in most gch.

My own tests for my setup are it costs me more to keep it on 24/7 (even at a lower setting) but for short durations it is better to keep it on but lower setting say 1-2 hours away.

If you compare with a car then running a car on tickover in first gear is less energy efficient then running at say 2/3 revs on top gear even though its using more energy over the same period its travelling further. By this I mean keeping your boiler on very low settings may not be the most efficient settings.

red_flump

Idiophreak wrote: »

they're binary systems, either on or off, so the temperature will actually wander between, say 17-19' for a specified temp of 18', in a peak-trough manner, as you see on a broader scale in the on-off model.

The new thermostat I fitted (Honeywell CM927) attempts to overcome this problem. You leave the boiler thermostat on full, and let the CM927 switch the system off and on in cycles as necessary. If the room temp is more than say a degree below the setpoint it switches the system on 100% of the time. As the temp approaches the setpoint it turns on the system for 50% of the time (in each 10 minute cycle) to prevent wasteful overshoot. Then as the setpoint is reached the system is on for just long enough to maintain the temp, 2 minutes min every now and then to nearly on all the time if its below freezing. The temp is maintained +/- 0.5C.
The advantage is only enough gas is used to maintain the temp, downside is that the system is cycled at lot more than a conventional stat. It also has optimum start which starts the system just early enough to reach the setpoint time you set, so later starts in milder weather.

Red

Cardew

red_flump wrote: »

The new thermostat I fitted (Honeywell CM927) attempts to overcome this problem. You leave the boiler thermostat on full, and let the CM927 switch the system off and on in cycles as necessary. If the room temp is more than say a degree below the setpoint it switches the system on 100% of the time. As the temp approaches the setpoint it turns on the system for 50% of the time (in each 10 minute cycle) to prevent wasteful overshoot. Then as the setpoint is reached the system is on for just long enough to maintain the temp, 2 minutes min every now and then to nearly on all the time if its below freezing. The temp is maintained +/- 0.5C.
The advantage is only enough gas is used to maintain the temp, downside is that the system is cycled at lot more than a conventional stat. It also has optimum start which starts the system just early enough to reach the setpoint time you set, so later starts in milder weather.

Red

The problem with some of us posting on this thread is that we know it is inconceivable that it could actually be cheaper to maintain a constant temperature, than letting the temperature fall at night or when out of the house. Our interest is in trying to quantify the savings of timed heating.

However the 'urban myth' that heating on 24/7 at a constant temperature uses less energy(cos it costs more to heat up from cold!) still(unbelievably) has those who believe it is Gospel.

Earlier today a new thread was started on the 'Fuel and other Heating' forum with the OP's opening post stating:

Central heating, what temperature?

I would be interested in knowing what people with central heating have their thermostats set to so I have set up a poll. You can post a message of you like as well.

Ours is set to 18C and is left on permanently, the beauty of it is the temp in the house very rarely reaches that so thermostat hardly ever has a reason to kick the boiler into action.

Almost, but not quite 'Perpetual Motion'?

red_flump

Cardew wrote: »

The problem with some of us posting on this thread is that we know it is inconceivable that it could actually be cheaper to maintain a constant temperature, than letting the temperature fall at night or when out of the house. Our interest is in trying to quantify the savings of timed heating.

We are all trying to balance cost, comfort and simplicity. I think some of the issues deal with how quickly the house gets back to the required temp. A colleague has also had a new boiler this year, in their bungalow they have it on at 18C all the time and up to 21C for the morning and evening periods. Different priorities.

Red

Cardew

red_flump wrote: »

We are all trying to balance cost, comfort and simplicity. I think some of the issues deal with how quickly the house gets back to the required temp. A colleague has also had a new boiler this year, in their bungalow they have it on at 18C all the time and up to 21C for the morning and evening periods. Different priorities.

Red

Absolutely! that what everyone strives to achieve.

Of course many don't bother too much with the room thermostat(some don't have them fitted) and simply control temperature in the various rooms with TRVs.

However that is a different issue from those who think that 24/7 at a constant temperature is the most economical method.

Jennifer_Jane

lightSwitch wrote: »

Can people mention what temperatures they run their house at please?

Between 25 up to 35 degrees - the wonderful plumber put the thermostat right next to the airing cupboard, not a place where I spend a lot of time.

Jen
x

colonelhall

Hi Cardrew,
Fancy come across you again, after so many posts on the "gas sculpting" thread. I knew that I had seen a discussion on this topic, some time ago. I have just recorded an enormous jump in gas consumption this week. In spite of being away for two days, with the gas off, I used more gas than in any week of last year.
I thought that perhaps my strategy of "gas off when out" was not working, so I tried to track down this thread. Fortunately, your well-reasoned argument has convinced me that perhaps it was just a very cold week.
In spite of my long arguments with Npower over the gas sculpting issue, they have REDUCED my energy bills for the coming year. This is no doubt due to me keeping a watchful eye on my consumption and turning off the heating when out. I only started this strategy in the Spring, so I was worried that it didn't apply in the Winter. Was it really that cold last week?