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Heating Control Answered

I have been thinking for some years now that I would like to have finer control over my central heating.

The problem
Now we are older we feel the cold more so in winter the heating is on all the time. This means that we have to keep altering the thermostat on each radiator at different times of the day or just leave them and so waste energy. One method means wasting energy but the other means rooms will be colder than we want initially.

The system and what i have
We have a combination boiler which has a digital timer and also on the panel are temperature controls for hot water and radiator temperature. Each radiator has a thermostatic valve so each room can have it's temperature set independently. I have a computer which runs 24/7 and also a bit whacker which I can control via python code and electronics has been a hobby for over 50 years

My idea
I would like to have some system which would allow me to adjust each room temperature via computer control.

Possible solutions
Solution 1
Fit a stepper motor to each thermostatic valve to adjust it at different times of the day/night.
This would allow precise control but would be quite expensive to set up.
Solution 2
Fit a small structure round each valve with a filament bulb or resistance wire in the bottom so that when power is applied to it then the temperature around the valve will rise and so the valve will close or, at least partially close.
I think this would be much cheaper to implement but would have the small on-going cost of using power to the bulbs whenever the room temperature needs to be cooler that it would normally be.

My initial plan
Build a small structure around one of the valves with a low voltage bulb in it. It would have vents at top and bottom and so air would circulate. I have a portable digital thermometer so i could gather information and try different bulbs to see how much power would be needed and therefore what the on-going cost would be. Also try various shapes of structure to see what the effect would be.

So guys what do you think?
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21 Replies

Roxer (author)2010-01-27

Have you considered a CM Zone system? It uses wireless signals to an HR80 wireless controller on each radiator. It also aggregates demand from radiators to optimise boiler firing. You can switch radiators between zones at any time in the future.  See www.cm-zone.com

buteman (author)2010-01-27

Hi Roxer,
No, I had not even heard of them. So I have had a look and as far as I can see I would need 3 controllers and 9 valves costing £873.57 plus delivery.
I think that I can do it the way I propose way cheaper than that.
Sure each will need wiring but there will be no plumbing to do.
Thanks for the thought though.

lemonie (author)2010-01-17

If you're not leaving the house empty for long periods I suggest this instead:

Turn the radiator water temperature right down, around body temperature. Leave the heating on continuously 24/7. Yes I've done it, and it works.
The boiler trickles heat in through intermittent burns, the place stays the same temperature all the time.
Hot/cold cycling will only save you energy with long off-times. See how much fuel the boiler burns up in the morning - think about that keeping the place topped-up overnight instead.

L

buteman (author)2010-01-17

I can see where you are going with this but I do not feel this would work as you describe.
Let's say I want to keep the bedroom warm from 22:00 to 09:00 = 11 hours.Then it can cool down over the next 13 hours. Similarly our living room would be kept warm from 08:00 to 22:00 = 14 hours. Then it can cool for 10 hours. and so on for the other rooms. Even with just those 2 it means that energy only needs to be used for part of the day. Having the water temperature low in the radiators only means the room will heat up more slowly it will not save energy. So having the unused rooms cooling down for a while will save some.

lemonie (author)2010-01-17

The rooms will not heat up or cool down, they maintain their temperatures. If you're both not out of the house for half the day why let it cool down? You have to pump a lot of heat in to get it up, then it dissipates through the walls, windows, roof and the cycle starts again.
The view is: how much energy does it take to "thaw something out" against keeping it warm. You're losing heat continuously until the building is stone-cold (then you start saving). I'm thinking that one/both of you are in more than you're out, but I may be wrong there?

L

buteman (author)2010-01-17

If the room starts cooling down at say 22:00 the it will cool fastest during the 1st hour. As time goes by it will cool more slowly. It depends on the difference in temperature between the room and the outside as to how fast cooling occurs. the rate is not linear. In the 1st 4 hours the temperature will have dropped by a greater amount than the next 4. Similarly when it starts to warm up it will warm up faster during the 1st 4 hours than during the next 4. While the heating is not on you are saving heat. I do not think it would take more heat in all that time to heat it back up as leaving it at a steady temperature as the steady temperature would be at the level of the highest difference between outside and inside. Of course the way to find out the actual values would be for me to build a little interface to my Bit Whacker which I can use to monitor the temp in a room overnight if I turn the heating off.  I have not built one before but i think it would be pretty easy to do.

I think I could feed a diode with a constant current and use one of the Bit Whacker pins as an analogue input and read off the voltage values and log them to a file. I will try to find time during the next week to do that and then report back.
If anyone has any other thoughts in the meantime please let me know.
I was going to say I don't want to build something for nothing but a thermometer like this would be useful for other things - like monitoring our greenhouse temp.

Great another use for the Bit Whacker!!!!!!

lemonie (author)2010-01-17

All the heat that goes out has to be put back in. While the boiler is not burning you are not using fuel, but this doesn't necessarily equate to saving heat, as it will still burn heavily when it turns back on. And one has to consider comfort levels as well.

L

buteman (author)2010-01-18

it is true that you need to put heat/energy back in the bring the room back up to temp. If you maintain an even temp all night then you are maintaining equilibrium so what goes out is balanced by what you put in. If the outside temp drops you get more heat going out so you have to put more in to keep the temp the same.
If you, instead, stop putting heat in the the temp in the room goes down. The greater difference between the inside and outside the faster the transfer of heat so as time goes by the rate of loss of heat goes down as the temp difference is getting less. While you are not maintaining the temp you are using no heat/energy.
When you want to bring the temp back up you do indeed need to add more heat. Imagine you want to just put exactly the same amount of heat back in per minute as you were doing to maintain the temp. Now your room temp will still rise until what you put in is balanced by what goes out. In practice the thermostats put more heat in per minute initially but and it's a big BUT only for a shorter period of time.
therefore you do save heat.

buteman (author)2010-01-18

Just to point out that I am trying to regulate the temperature of each room independently so that each room is at a comfortable temp at any time we are using it. We tend to be in a room for the same periods of time each day but by controlling it via a computer program I would be able to have a virtually infinite range of control day to day and hour to hour.

lemonie (author)2010-01-18

What about plumbing-in solenoid valves? Thermostatic valve one end, electrically-operated the other (of radiator)

L

buteman (author)2010-01-18

Hi,
I have looked at that option.
Good points: low voltage valves available. fairly straight forward plumbing job. Can be bought for about £12 each so ~ £120 overall with delivery costs. Reasonably low power requirements.
Bad points: Will mean 3 valves on each rad - the present manual valve has to be used to balance the flow through the various rads.  This would, I think, look worse than  what I could devise using the method I am suggesting.
So now 2 things to do to see how feasible it would be.
Any further thoughts would be appreciated.

lemonie (author)2010-01-18

You've got one thermostatic valve for three units? Would you be able to add a plumbing-diagram to this topic, it might help people (in general) solve this one.

L

buteman (author)2010-01-19
No, perhaps I didn't explain very well.
At present:
inlet pipe-> Thermostatic valve -> rad-> manual valve-> outlet pipe.
The manual valve is adjusted on each rad so that with each thermostatic valve wide open there is as far as is practical an equal flow of water through each rad.
This is needed because flow to each rad  otherwise depends on at least all the following: length of pipe from pump to rad + height of rad above pump + diameter of pipe + roughness of inside of pipe + number of bends.

so the manual valve needs to remain.

What would be needed;
inlet pipe-> Thermostatic valve-> rad-> manual valve-> solenoid valve-> outlet pipe.

Hope that explains better and why I think it might be either unsightly or more work such as hiding one of the valves behind the wall but providing access for servicing/replacing.

lemonie (author)2010-01-19

Hmm. I don't think you've explained it badly, but a plumbing diagram would help. If you're switching rad's on/off the manual flow-adjust becomes redundant. For heating-up you might as well have maximum-flow until the thermostatic valve starts to actuate?

L

buteman (author)2010-01-19

Sorry lemonie but I disagree. If the heating pump cuts out due to blown fuse or power failure or for some other reason then when it comes back on all thermostatic valves will have started to open up to try to keep the rooms warm. If it has been a while then they may all be fully open. Without manual valves we will have the problem they are there to prevent. By using a heat source under the thermostatic valves they will close because they sense this as meaning the room temp is above what is required. When the heat source is turned off they will start to open as normal and it will be fine.

lemonie (author)2010-01-19

I'm working from the vision of you having an electronically-controlled-valve on each unit. If your pump fails, when you restart the system you'll only be heating the rooms which you have selected to be heated at that time of day, and you want those units open at that point.

L

buteman (author)2010-01-19

Yes that's right, that is what I am trying to do with this idea. If the pump fails and then I fix it all the thermostatic valves will be fully open when I restart it. Because I am leaving the manual valves in place it will, initially, be no different than if I switched the heating off overnight for example. At the same time the control system I am proposing will come into play, the thermostatic valves on the rads I do not want on will slowly close and everything will come back into balance.

Kiteman (author)2010-01-17

It may sound condescending, but the way we responded to dropping temperatures was to wear more layers.  Far cheaper, and completely independent of rooms.

buteman (author)2010-01-17

Yes i had thought of that and it's what we did when we were younger.
Perhaps I should have put that option in my question and then explained why it is not applicable to our situation.

It might be cheaper but it isn't independent of rooms as far as I can see.
My wife has serious health problems and I have a chronic condition which affects me quite seriously sometimes and barely at other times.
We need to try to keep comfortable at all times so if, for example, I program the heating to turn off each night and back on in the morning then, when I need to help her during the night it is not always very practical to 'wear more clothing'.

Kiteman (author)2010-01-17

Ah, I see.

It is possible to get individually-programmable radiator thermostats. They work by reducing the temperature at pre-set times, so you set the whole house "warm", and the 'stats cool certain rooms at certain times.

buteman (author)2010-01-17

Didn't know about them. Just had a look and found they are over £40 each.
With 9 rads thats over £360 and that is without delivery charge.
This encourages me to do some testing.
I already have a bit whacker and am comfortable with writing python scripts. I have a PC which is on all of the time because it is used as a server for myself, family and friends. So I guess I will start working out how to do it.