General thoughts about heating

[Nad]

I was having a chat to someone about heating over the weekend and he said that he finds it more economical to keep his bungalow at a constant temperature than it is for the heating to be off when no one is at home and then come back on when people are home.

In his opinion its more economical because the fabric of the building (it's a relatively newly built bungalow) remains warm so the heating system just keeps topping up what's there rather than making the heating system warm up a cold house every day.

I'm going to see if i can get some quantitative data out of Cortex to see how this theory works in my house but i was wondering about other people's opinions and thoughts

So please ... discuss

[Gangsta]

Thats exactly what I do in my bungalow - I have to agree with your friend. And even if we are wrong - i still prefer to come home to a nice warm house - even if it does cost a few quid more.

[toscal]

What temp do you have. I'm thinking if you have the heating on all day then you can drop the temp a bit.

[MrFluffy]

On my last house which had ufh upstairs and down with a control system I made from scratch myself I used to drop the downstairs floor temperature during the night and start bringing the two zones back up about 5am, so when we risen at 7.30 onwards it had chance to recover.
Ditto for upstairs, during the day we reduced the floor temperatures as occupancy wouldnt be very high. Unless it was a sunday, in which case it used to bring downstairs up to temp but keep our bedrooms higher till 10am just in case a miracle happened and we got a lie in (we've got two young kids... it never did).
What we also did during very cold days outside was raise the floor temperatures by a amount which was a factor of the difference in temperature between indoors and out. Being that on really cold days my mrs would always want the house warmer to compensate somehow.
Im not certain how much it saved us as I never fitted sensors to see electricity consumption from the 3 phase immersions and logged it against time (could have done if I was bothered), but it seemed sensible, and given we only had 9kw peak of heating available for a house 50m2 per level things seemed to be able to keep pace with the surge in demand at raising things up time.
My mrs wants me to dump the control pack that came with our current ufh kit on our new build and fit my old system to this house too so we can do the same scenario to minimise fuel useage, which Im in the process of doing (only this time I want it to cover the wood burning furnace needing fuel and a few other bits n bobs)...

[MichaelD]

The only way that you friend could know that its more economical to keep the heating on is if he's done a long-term comparison. I'd love to see his data!

Three things to consider:
1) the only heat you pay for is the heat that escapes out of the house. If it all stayed in the house then your bills would be £0. The rate of escape for heat is based on the difference between the temperature inside and the temperature outside. If you keep the inside hot for longer, you will lose more heat.
2) modern gas boilers are more efficient if they run hard, in condenser mode. if they are just topping up the heat a little, then they can stop condensing and will become less efficient
3) the pump usually consumes around 100w, so that is £100 a year to keep it running, even if it isn't sending any heat round.

[Otto-Mate]

We were told that too - run it 24/7 at low temp.

When we did that though we burnt through £100 per WEEK in heating oil and couldn't afford that.

While there's no doubt underfloor heating is lovely, I regret putting it in. We can heat the bedrooms upstairs (rads) quickly and much more economically. Underfloor is too slow to react to use it like that.

We now use the underfloor a bit in the kitchen when its really cold, plus a wood burning stove in the main living area.

M.

[TimH]

The only way that you friend could know that its more economical to keep the heating on is if he's done a long-term comparison. I'd love to see his data!

Three things to consider:
1) the only heat you pay for is the heat that escapes out of the house. If it all stayed in the house then your bills would be £0. The rate of escape for heat is based on the difference between the temperature inside and the temperature outside. If you keep the inside hot for longer, you will lose more heat.
2) modern gas boilers are more efficient if they run hard, in condenser mode. if they are just topping up the heat a little, then they can stop condensing and will become less efficient
3) the pump usually consumes around 100w, so that is £100 a year to keep it running, even if it isn't sending any heat round.

The other thing to consider is how your property is constructed and where the thermal mass is in relation to the insulation. "Lightweight", well insulated houses respond quicker to changes in your heating whereas "heavier", equally well insulated houses tend to have slower responses.

The obvious example is UFH vs radiators. When heating UFH you have to warm up the slab before you start to transfer heat to the room, this all takes time and means you response is slower. Radiators heat up faster, but will also cool down quicker, while the UFH slab will continue to radiate heat long after you've turned the heating off.

Your lifestyle and occupancy patterns also affect how you might want your heating to behave. If you're out working all day, perhaps you want a faster-responding system that you can turn off in the morning and that will only come on again just before you get home. If you work from home a slower responding system might be more suited to maintaining more even temperatures over the whole day.

As was mentioned though, the more insulation you have the better - energy prices are only going one way

HTH,

Tim.

[toscal]

While there's no doubt underfloor heating is lovely, I regret putting it in. We can heat the bedrooms upstairs (rads) quickly and much more economically. Underfloor is too slow to react to use it like that.

We now use the underfloor a bit in the kitchen when its really cold, plus a wood burning stove in the main living area.

M.

Interesting. We have ufh in 2 rooms, ours is electric. But it will heat up the room in less than 20 mins. We laid 10mm Marmox boards on the floor first then laid the heating cable and just tiled directly over the heating cable. So the heat doesn't have far to travel.
Do you know the tube spacing used for your underfloor heating. As this can have an effect on heating efficiency. From memory we used a 60mm spacing for the heating cable.

[MichaelD]

We were told that too - run it 24/7 at low temp.

When we did that though we burnt through £100 per WEEK in heating oil

M.

Oil fired boilers use an amount of oil to start up, so each startup wastes some oil that doesn't translate directly into heat for the home, so if running at a low level of heating, they will cycle on and off a lot, and those startups really squander the oil.

Don't have any evidence for this, but they are probably at their most efficient when running at a constant level for a time, then switching off, which is exactly what you get if you let them go off during the day when everyone is out, then run them for two or three hours to get everywhere warm in the evenings.

[chris_j_hunter]

>I was having a chat ... please ... discuss ...

Tricky one - we’re pretty sure 24/7 is going to work well for us (*) but it really depends on the set-up & how it matches the situation. Not all UFH systems are the same, not all radiator systems are the same, not all houses are the same ... ditto boilers, control systems, families, locations ... everything depends on how the various factors come together, how well the bits work together & how little they fight each other ...

We’ve dug a bit into this, and a lot of the important factors seem to have been mentioned already - ventilation arrangements & how things are sensed & controlled might be things to add to the list - and modulating burners, thermal store buffers, mixer-valves, and weather-compensating controls, might be able to help improve things, even overcome existing problems, especially over-cycling, but only as part of a coherent total-approach, in which details can matter a lot ...

Big things to try to avoid must include frequent cycling, poor insulation, poor ventilation / air-tightness, and people adjusting the thermostats every time the wind blows, so the system is always trying to catch-up ! Ditto things fighting each other - eg: return flow from radiators being too hot for a condensing boiler to condense ! Generally speaking, running the heating as cool as possible will be more efficient, and UFH can help with that. Also, as with cars, even-ness is more economical than ups & downs - ie: constant speed & no hills for cars / constant temperatures for houses - but absolute economy will vary with speed / temperature, and fuel used will also depend on how long the engine / heating-system is running-for !

Another thought - comfort-wise, using a black-bulb sensor might be the best way to measure temperature - a well-placed one will get pretty close to picking-up all the thermal comfort factors, pretty much as people do - ie: the particular mix of air temperature & radiative temperatures, coming from walls & floor, ceiling & windows, appliances, fixtures & fittings, fires & radiators, whatever. The warmer things are, the more heat they radiate. Even with the heating on full-blast, we can feel cold if the walls are cold, or a cold draught is getting-in, or it’s sub-zero outside & we get a good view of it through the window. Heatmiser do them, others too, and they’re not expensive - a quick Google found these, for example :

http://www.havelockcontrols.co.uk/itemdetl.php?itemprcd=52321003

http://www.heatmisershop.co.uk/products/Black-Bulb-Sensor.html

http://www.titanproducts.com/categories/1_32_134_16/Room_Temperature_Sensor_Black_Bulb.html

Chris

(*) someone’s home all day, so we’ve designed for that - sorry !

[toscal]

don't know how much this would effect a heating system,but I do know our underfloor heating stats base their operation on the day before. So if it took 15 minutes to come to temp when it first comes on, then it will start the heating process 15 minutes earlier the next day. Also once at temp it can then automatically vary the amount of current going to the heating cable, bit like a dimmer switch. So its very rare that its actually full on once its at temp.


Heating control can get a bit like rocket science as there are so many factors to think about. From looking at outside temp and using this combined with inside temp to decide when to start the heating.
Then you then have the occupied and unoccupied heating cycles.
Only heating occupied rooms and having unoccupied rooms set to a lower temp.
Now combine all of this together = headache and you will always get someone who will fiddle with the controls.

[chris_j_hunter]

>heating control can get a bit like rocket science ...

yep, if ever we get a bit of time free (joke) I'm sure neural nets could be worth a look, for doing it better, through a mix of pattern recognition / curve-fitting / and learning - it would need lots & lots of data, but then a good HA system will be carefully collecting & storing-away plenty of that !

Chris

PS: in case anyone is feeling brave, the link we have stored away to get us started on a neural net approach is this one - very brief & to the point, with links that are equally so, and none of it needing a math's degree, just some persistence :

http://en.wikipedia.org/wiki/Backpropagation

'could maybe use a spreadsheet like Excel to play with some ideas for hidden-layer formulae, and when a useful set of them results, stick it in a macro for the HA to use ...

well, that's the idea, and maybe something will come of it ? (!)

[toscal]

>heating control can get a bit like rocket science ...

yep, if ever we get a bit of time free (joke) I'm sure neural nets could be worth a look, for doing it better, through a mix of pattern recognition / curve-fitting / and learning - it would need lots & lots of data, but then a good HA system will be carefully collecting & storing-away plenty of that !

Chris

PS: in case anyone is feeling brave, the link we have stored away to get us started on a neural net approach is this one - very brief & to the point, with links that are equally so, and none of it needing a math's degree, just some persistence :

http://en.wikipedia.org/wiki/Backpropagation

'could maybe use a spreadsheet like Excel to play with some ideas for hidden-layer formulae, and when a useful set of them results, stick it in a macro for the HA to use ...

well, that's the idea, and maybe something will come of it ? (!)

Well funny you should mention that. I did something similar a long (about 20 years ago) time ago. It was a spread sheet that would predict data values. And no it wasn't using the forecast, trend or average functions. It would take the previous results and a few other known variables to predict the next data value. It actually worked very well, so well that when a data value got corrupted we quite often used my spreadsheet value. The basic sheet took about an hour to do and then I would tweak it during each session. So it took about 3 months before it was really good.
Now I know its possible to feed ASCII serial data strings into Excel, but I can't remember how to do it, well it was over 15 years ago when I did that for another excel project..

[chris_j_hunter]

yep, that sort of thing - only this would be more automated & more generalised, using Excel to play initially, to try ideas & options, and then programming it up & (automatically) trying a vast range of functions & weightings until something good-enough turns-out ...

ie: take inputs from whatever array of sensors there are (measuring whatever, wherever, the more the better) and feed them into an array of functions (S-curve, normal distribution humps, whatever) to generate outputs that are combined in some way (whatever seems sensible) to produce an array of results ... compare those results with what's wanted (ie: comfort factors - temperature, humidity, lighting levels, whatever), and go-back & play-with & adjust the weightings & functions & combination connections until the results are what's wanted ... and do this over & over & over in some sort of incremental way, with inputs coming from as many circumstances as possible (weather, occupancy, whatever), and then freeze it & use those functions with those weightings & connections to run the whatever it is (heating, lighting, etc) ... and trying lots of functions & weightings, until something works !

OK, all this might sound daft, and people might think I'm daft (more than likely), and it is certainly a mix of science & intuition & luck - but such an approach has been found to work magic more than few times, in other fields (outside of HA) ...

[toscal]

OK, all this might sound daft, and people might think I'm daft (more than likely), and it is certainly a mix of science & intuition & luck - but such an approach has been found to work magic more than few times, in other fields (outside of HA) ...

Your not the only one.

Now where did I put that Excel sheet, its got to be on a floppy somewhere.