Gas on constantly or on and off...?

Cardew

stevemcol wrote: »

Cardew, et al, I know you get frustrated and I agree, your physics are correct. However, as you point out, there are other variables. Some of the posters above are coming across the same problem I had: allowing the house to completely cool makes it very difficult to heat it up again. Allowing the boiler to tick over during the day is one solution THOUGH I AGREE IT'S NOT THE CHEAPEST. If people don't grasp the physics they are not 'stupid' or 'idiots'. Will you just contain you inner angst and calm down. If the thread upsets you so much, just avoid it. If you can bring yourself to read it without exploding in a fit of rage, please use your knowledge and expertise to dispense sensible, practical advice to help people maintain a comfortable temperature by the ceapest means.

You possibly haven't seen this thread?

https://forums.moneysavingexpert.com/discussion/2907196

This particular poster is not shy in handing out comments - read post 45 onward - below a reply to JasX who does know what he is talking about.

Please read my post again, before you look foolish once again!

So he is no shrinking violet with barbed comments!

It has been stressed time and time again that we all have to strike a compromise between cost and comfort.

However people like him just will not accept the Laws of Physics, all technical advice etc and insist 'they have proved' that having heating on 24/7 is cheaper than timed. Not more convenient - cheaper.

Not content with posting nonsense in one thread, he now post the same here.

The trouble is people believe him!

oellph

I have to jump in here too

Let's try this:

Scenario A: Leaving boiler on constantly, as low as possible, using TRVs to control which rooms are being heated. Temperature maintains around 16-18c most of the time.

Scenario B: CH set to come on for 2hrs in the morning and 5hrs in the evening, boiler set to 2/3s or higher to heat the house during those limited times. (Lower setting means it never achieves that goal). House heats to 16-18c during those times, but at other times drops to 10-12c.

Scenario C: CH governed by room thermostat, set for 14c during the day, 16-18c during the evenings and mornings.

Scenario As per C except house allowed to cool to 10-12c during unoccupied times.

So in my mind in scenario A, after the initial first few days, the boiler won't be on constantly and when it is on it will be using less gas. In scenario B it will burn harder for shorter amounts of time, but this will even out or use less gas (depending on how well constructed the house is) than A.

With C, the boiler will be firing almost as much as scenario A because it's trying to maintain a good temp when the house is unoccupied. Scenario D uses room thermostats to achieve results much like scenario B.

I've been doing tests myself during this cold snap, partly out of necessity to keep our babies room warm during the night (with heating off it drops to 12-13c). On timer (2hrs morning, 5hrs evening) we're using around 8-9 units a day (m3, condensing combi, 4 bed semi, open plan downstairs). Keeping it on low overnight, and turning RADs in every room except the babies to 1, we're using about 13 units per day. Strangely turning rads down in other rooms doesn't seem to help all that much.

Just before the heating goes off at 10pm the babies room is at 17-18c. (It's above a garage and has a small rad). That temp drops off too quickly for us during these exceptionally cold periods. At other times it's fine.

Jon_Tiffany

A boiler will be at its most efficient when the water returning from the radiators is at a low temperature. This is more likely to be the case when the heating is left on for a long period, as it is just topping up the heat.

A short burst of high heating will mean hotter return temps and the boiler being less efficient.

I believe this is the source of the myth about it being cheaper to leave heating on low.

Cardew

Jon_Tiffany wrote: »

A boiler will be at its most efficient when the water returning from the radiators is at a low temperature. This is more likely to be the case when the heating is left on for a long period, as it is just topping up the heat.

A short burst of high heating will mean hotter return temps and the boiler being less efficient.

I believe this is the source of the myth about it being cheaper to leave heating on low.

You are really referring to condensing boilers here, and this myth has been around long before those were invented.

Indeed the same myth applies to electrical heating - that 'topping up' is cheaper.!!!

The basic fact(law) is that a house with an internal temperature of say 19C will lose less heat than the same house at 20C. 18C less than 19C and 17C less than 18C etc etc.

So if heating is off and temp of house drops to say 17C it will be losing less heat than it would if the temperature were to be maintained at 20C.

If someone maintains it is cheaper to have heating on constantly rather than off for some hours.

Then it must still be cheaper to have heating on constantly if you go away for a few days, a few weeks, a few years and have the heating off. It is exactly the same principle.

The same as the oft quoted example of a kettle. If it is cheaper to have it at a constant temperature, why don't we leave the kettle simmering all day; rather than let it go cold and have to heat it up.

inaminute23

Cardew wrote: »

You are really referring to condensing boilers here, and this myth has been around long before those were invented.

Then it must still be cheaper to have heating on constantly if you go away for a few days, a few weeks, a few years and have the heating off. It is exactly the same principle.

The same as the oft quoted example of a kettle. If it is cheaper to have it at a constant temperature, why don't we leave the kettle simmering all day; rather than let it go cold and have to heat it up.

Please answer this. When my lounge drops to 15 deg overnight, how long should it take to get to 20 deg, taking into consideration it is fairly well insulated, and has suitable size radiator?

inaminute23

oellph wrote: »

I have to jump in here too

Let's try this:

Scenario A: Leaving boiler on constantly, as low as possible, using TRVs to control which rooms are being heated. Temperature maintains around 16-18c most of the time.

Scenario B: CH set to come on for 2hrs in the morning and 5hrs in the evening, boiler set to 2/3s or higher to heat the house during those limited times. (Lower setting means it never achieves that goal). House heats to 16-18c during those times, but at other times drops to 10-12c.

Scenario C: CH governed by room thermostat, set for 14c during the day, 16-18c during the evenings and mornings.

Scenario As per C except house allowed to cool to 10-12c during unoccupied times.

So in my mind in scenario A, after the initial first few days, the boiler won't be on constantly and when it is on it will be using less gas. In scenario B it will burn harder for shorter amounts of time, but this will even out or use less gas (depending on how well constructed the house is) than A.

With C, the boiler will be firing almost as much as scenario A because it's trying to maintain a good temp when the house is unoccupied. Scenario D uses room thermostats to achieve results much like scenario B.

I've been doing tests myself during this cold snap, partly out of necessity to keep our babies room warm during the night (with heating off it drops to 12-13c). On timer (2hrs morning, 5hrs evening) we're using around 8-9 units a day (m3, condensing combi, 4 bed semi, open plan downstairs). Keeping it on low overnight, and turning RADs in every room except the babies to 1, we're using about 13 units per day. Strangely turning rads down in other rooms doesn't seem to help all that much.

Just before the heating goes off at 10pm the babies room is at 17-18c. (It's above a garage and has a small rad). That temp drops off too quickly for us during these exceptionally cold periods. At other times it's fine.

What is your stat set at? With mine set at 19 deg, it uses around 1.8 units overnight

inaminute23

From about the end of September to the present i have used approx 150 units (4740 kwh)of gas with the heating constantly on, set at between 19-21 deg celcius. My house is a 3 bed, with a total of 10 rads which run off an 18month old Halstead ace he30 combi boiler.

oellph

We don't have a thermostat - just the boiler setting and TRVs. Boiler, up an till recently, was on 1/3. From 28th Sept to 27th Nov we used 326 m3. Four bed house, open plan down stairs and gas used for heating, cooking and hot water. Again, until recently CH was set to 2 hours in the morning and 5hrs in the evening. We were averaging about 60kwh per day, or about 5 units per day.

davecon1

This discussion seems endless but I've been trying to work out the most cost and fuel efficient to heat my house.

We're in a 4 bedroom end of terrace house with no cavity wall insulation and rubbish double glazing (very thin). The thermostat is set to 18 C and all the rooms have programmable thermostatic valves which are set low.

So far the heating is set to come on at 7.10am-8.30am and from 7.10pm-10.30pm. During the cold spell I've been checking my gas meter (cubic feet) and typically use 3 units over a 24 hour period and since Nov 21st we have used around £55 gas according to the smart meter site.

Now here is the interesting bit. Recently I have been working from home and have had to resort to having the heating on all day (thermostat still on 18 C). As I'm downstairs most of the time the rads upstairs are off (no sense in heating an empty room) BUT my gas consumption has been exactly the same for 12+ hours as it was for 5 hours. The outside temperature has been more of less the same each day (around 1C during the day and -1C at night).

Without being called a simpleton etc can someone please explain how this can be possible? I do understand that leaving your heating on all day should in theory massively push up your bills (vs leaving it on timed while you are out) BUT my recent tests seem to show that this is not the case as I was expecting my usage to almost double!

Any advice or comments?

inaminute23

oellph wrote: »

We don't have a thermostat - just the boiler setting and TRVs. Boiler, up an till recently, was on 1/3. From 28th Sept to 27th Nov we used 326 m3. Four bed house, open plan down stairs and gas used for heating, cooking and hot water. Again, until recently CH was set to 2 hours in the morning and 5hrs in the evening. We were averaging about 60kwh per day, or about 5 units per day.

Get a stat! TRV's are useless unless you know what temperature each setting on the trv represents. It sounds like the trv's are calling for heat all the time. Install a room stat where you frequent the most and open all your trv's up. If you are happy to not use some rads and they all have trv's then i think you need to turn the lockshield off aswell. The temp is dropping that much at night, even on setting 1 the trv will call for heat.