How much does control methods change the fuel used in central heating?

[ericmark]

Clearly the hotter the home, the more fuel used, I am not talking about that, what I am talking about in the main, is the latent heat extracted from flue gases, and the effect of sine wave temperature control. We have been shown the diagrams for years, also the circulation diagrams and the argument as to where the radiator and the thermostats should be placed. And I know due to getting it wrong, it does matter, but the theory can't always be done in practice, putting the radiator against an internal wall reduces losses through the wall, but then one is left with any wall thermostat being on an outside wall.

The whole idea of the TRV seems great, but with modern electronic TRV heads, we see the temperature it sees, which are often much lower to what a wall thermostat sees. Double-glazed windows now have larger gaps, and are much improved, we add loft insulation, cavity wall insulation, and the home it nothing like it was when built, and central heating installed.

Boilers have been changed, often in the case of gas to a modulating type to help extract latent heat, then fitted with a thermostat using mark/space control completely upsetting the control built into the boiler.

But the question is, how much will getting the control wrong, really cost? Or the other way around, how much with OpenTherm and the like control save? Also, rather simple things like raising butt hinges. We have rooms in our homes, how much will closing the doors between rooms, help on reducing heating costs?

We have rooms which are not used much, and we will turn down the TRV in those rooms, but then leave the door open. But get some thermometers and place them around a room, and one can see the temperature variation even in one room can be 6ºC. With bay windows and morning sun, even more.

As to what feels warm, sometimes 18ºC seems warm, other times feel cool at 22ºC, I find I want it cool at night, 16ºC when in bed is ample, on arising I want it warmer, maybe 19ºC, but come the evening, want it warmer again around 21ºC, so response time becomes a problem, and the times I have felt cold, only to hear minutes latter the boiler fire up.

Also, there is the room which always seems cold, is it worth running a whole central heating boiler, to heat one room?

And warming rooms when energy is cheap, rather than when needed. This more down to electric, but combined power is an option.

I have always considered having something like Drayton Wiser and each room independently controlled was the bees knees, but @Mister Banks tells us

On my Wiser system I now only have a single room thermostat having now removed all the Wiser TRV’s and replaced them with manual TRV’s.

It seems he has more info as to how the heating is working to me, Google Home allows me less not more control to the thermostats own app.

But when someone rips out the control, one has to ask why, has the modern control gone OTT.

 

[bernardgreen]

But when someone rips out the control, one has to ask why, has the modern control gone OTT.

Why ? it has gone way over the top.

Why have a bi-metalic thermostat when one can have a micro-processor chatting with an internet server hundreds of miles away from the house.

 

[ericmark]

We have water and electric control, the water control can adjust the output of each radiator as required, and with a modulating boiler can in conjunction with the by-pass control the boiler output. Where it falls down, is it can't tell the boiler to turn on/off, it can only control up/down, so this time of the year, when a cold snap may arrive, we want some automated way to turn the boiler on/off.

The bimetallic thermostat with neutral not connected is likely ideal in a one room home. The 1.5°C between on/off actually helps, so boiler not turned on for a few minutes.

But I do not live in a one room home, my living room now 22°C wall thermostat (18.5°C and 20°C on the TRV heads), wife's bedroom 17°C, dinning room 15°C and the hall 15°C at TRV and 21.5°C wall thermostat. The latter is a huge difference for the same room, 6.5°C one end of the hall to the other. I have removed the TRV head and hung it on the wall thermostat to see if they match, and they do.

At 17°C in the wife's bedroom, that is within limits, but when it gets to 14°C clearly the room needs heating, but the radiator is next to the window, when running heat from the radiator will tend to mean it shows a little higher than the room really is, due to limited air circulation, and the reverse when not running.

So there is a case for maybe having a wall thermostat in her room, and linked TRV heads in the living room? Down to air circulation.

But tried geo-fencing, OK not with Wiser, it was with Nest, and it detects the phone too close to home, for the heating to heat up home in time. It did turn off heating as we left, or switch to Eco mode, which is a lower temperature, seem to remember 16°C and 20°C were Eco and Comfort setting, but it never cooled to 16°C anyway in the time we were away.

What was the final straw, was the local EE mast went down in high winds, result it turned heating to Eco mode, however the Thermostat has a built-in PIR, so as we walked past it, the thermostat changed to comfort mode. It took a day to realise why we were so cold, only when I looked at the thermostat on the PC did it click what was going on.

So I think every smart option on the Nest wall thermostat has been turned off. We can change the temperature with the phone it saves us getting out of the chair, but as to altering while miles away, why would we want to?

Cooling different, we will look at the room temperature before returning from shopping, and if too hot turn on the AC, but the only reason for that is there is a limited capacity for condensate, and if left running for an extended time, we would return to a pool of water on the floor.

 

[oilhead]

It has only gone over the top for people who have too much time (and money) on their hands.

 

[Mister Banks]

In my case I have a conventionally designed 2 story house, by conventional I mean it is roughly square. Originally the heating temperature was controlled by a mechanical bi-metallic thermostat that overshot and undershot all the time causing roughly 4c swings in temperature. This wasnt comfortable so I looked for an alternative and after a bit of research decided on the Drayton Wiser system, thermostats and TRV's. After running this system over three winters I have concluded that heating at an individual room level is not for me and costs more in energy. I can see no benefit to heating rooms at different temperatures in my house and i see no benefit in the boiler firing to heat one or two rooms, I have also observed a TRV in one room firing the boiler for a few minutes and then a few minutes after the boiler has turned off another TRV fires the boiler for a few minutes etc, etc.

I now just have a Wiser room thermostat controlling when the boiler fires and conventional TRV's on the radiators.

 

[ericmark]

I do appreciate your reply, I had only considered when central heating is running, and thermals established, but before that happens the air in the room can have stratification, with the air at TRV level much colder as air at wall thermostat level. I am as you say having a problem with boiler firing up for a very short time in the morning.

I only have one linked TRV head, the rest are programmable, but not linked. 14 radiators in the house, like your's square detached, but three stories, and alternative heating in some rooms, and two sets of patio doors, three standard doors to outside, and some rooms simply not used in winter, so frost protection only.

I do need my wife's bedroom to call for heat, as often colder than hall or living room where the two wall thermostats are, but maybe better with a wall thermostat, and use the linked TRV elsewhere?

 

[Mister Banks]

From what I recall of your heating controls I think you have too little consistency and too much conflict. If it was me I would just go with one control system, like Wiser, and use a mix of Wiser TRV’s in the most often used rooms and conventional TRV’s everywhere else. If you need more accurate temperature control in any room then add a Wiser room thermostat to the room.

The radiators/rooms with conventional TRV’s can be setup to only heat when a Wiser TRV or room thermostat requests heat.