Heating thermostat in the hallway

[John Brown]

Mine is too old and primitive to accept an external sensor of any kind.

 

[NewbieRaf]

Someone in an earlier post mentioned Tado smart heating. I installed Tado smart radiator thermostat heads to all my thermostatic radiator valves, I ignore my central thermostat which is set to max or bypassed, these give precise temperature control to all rooms and can be set to come on at different temperatures at different times of the day or night.
The system can detect open doors or windows and switch off heating or turn on and off heating when you leave or return calculating how long to achieve the desired temperature.
I would say my system paid for itself in the first year of use and makes for simple control especially if you use Echo or similar devices for voice control.
I has proven particularly useful when away in winter as you can monitor the temperature of the rooms from your smart phone app.
I know there are other similar systems but I only have experience of this system and it knocks manual TRVs into a cocked hat as they say.

That was me and I do the same just the other way round since I have a Nest stat and Tado TRVs. I set the TRVs to temp and control the nest

 

[Dibs-h]

I removed the regular TRVs a few years ago and fitted Honeywell Evohome including the wireless heads (skipping the cloakroom rad - effectively leaving that as the bypass).

Very pleased with the whole setup although recently 2 heads were reporting as dead battery. Even replacing with fresh batteries - yielded no change.

A few mins with a small screwdriver - levering the "prongs" at the bottom the batteries sit on, upwards a mm or so - everything back to normal.

All the rooms can have their own schedules and if you have the WiFi gateway (version) you can control it all from your phone.

When gas prices were "normal" - I calculated a payback of 3.5-4 years on a spend of £650 based on actual gas usage (the controller and 2 packs of 4 heads - although we are only using 6 heads). With "current" prices - I've probably gone past break-even.

 

[dgs2001]

Let's see....

Yes, adjacent rooms will lose heat into the cold room. Therefore they will either be slightly colder than before {A} or they will draw more energy from their heat source to maintain their temp {B}.

In {A} another room will be cooler than before, therefore less heat loss to external = even more savings.

In {B} I need to show that the extra heat output from the remaining heaters is less than was coming out of the turned off heater. ie that the total heating energy is less. To show that with the details (individual temperatures and radiator outputs) requires running the 2 detailed models against each other. But again I can simplify by choosing my system boundary as the external walls, and we are back to: if every external wall is at the same or lower temperature then the heat loss will be less.


edit: There doesn't need to be a heater to turn off, closing the door on an unheated bedroom will also lower the delta temperature across some external walls which will reduce heat flow to outside.

I'm sorry I cant accept -

In {A} another room will be cooler than before, therefore less heat loss to external = even more savings.

Another room has become cooler saving some money in that room, however we are looking to achieve a constant set temperature in the adjacent room {B} but this now requires more energy to maintain our set temperature as the heat loss from this room has increased due to room {A} being a lower temperature, furthermore the barrier between {A} and {B} is of no real use as a heat insulator. Its just an internal wall.

Having access to an MCIS approved heat loss calculator I can confirm the net result of a substantially cooler internal space adjacent to a heated space is more energy being needed to heat the heated space.
Furthermore the now cool space will be occasionally used and required to be a heated space and if used enough it will be cheaper to maintain this as an intermediate boundary space with a small uplift to usage (warm space) temperature rather than heat from cold, especially when factoring in the uplift in heat input (cost) required to maintain adjoining warm spaces when colder rooms are colder.

As I said understanding Use is a vitally important part of this puzzle.

 

[John Brown]

Heat loss is always proportional to temperature gradient.

 

[dgs2001]

You allowed for comments so here they are I'm not a professor but a mechanical engineer who got A's in thermodynamics.


1). Letting the temperature fall lower and then reheating [A] will use less energy than maintaining at an intermediate temp and then re-heating .

To model this for sizing say a boiler would need delta temperatures and heat capacities and heat conductance values, not too hard (but hard in text format) and also not general. But there's an easier way to think about it, which is to only look at the heat loss which is proportional to delta temperature. At every time point the indoors/object temp is lower or equal in scenario A so the total heat loss is less. The start and end points of each scenario are all the same Temp so there are no stored energy deltas to complicate issues.

In [A] it will take longer to heat the house from the decision point to turn the heat up, but that will only save additional energy by being less responsive.


2). Turning off the heat in a bedroom and closing the door will save energy.

Again we only need to look only at the external heat loss. The inside temp of the bedroom external walls and windows will be lower than when the room was heated, therefore less energy will be flowing out through those walls.

Note: You haven't replaced an external wall by an internal wall; You have added an internal wall and 12 foot air gap to the same external wall.

Heat loss is always proportional to temperature gradient.

Surely heat loss is proportional to temperature gradient AND distance from the equator which dictates average yearly weather data AND the make up of the material heat is being lost through

 

[dgs2001]

That was me and I do the same just the other way round since I have a Nest stat and Tado TRVs. I set the TRVs to temp and control the nest

With no suggestion of money saving in mind, have you seen the Tado Control stat which would replace your nest is £99.99 in Screwfix?
It would allow you full use of the Tado app and control system along with utilising the Tado app to create all your wireless TRV heads as separate rooms/zones

 

[John Brown]

Surely heat loss is proportional to temperature gradient AND distance from the equator which dictates average yearly weather data AND the make up of the material heat is being lost through

So what? Given the same distance from the equator, and the same insulation, it's proportional to temperature gradient. I filled my attic with red herrings. Works well, but smells a bit in summer.

 

[dgs2001]

So what? Given the same distance from the equator, and the same insulation, it's proportional to temperature gradient. I filled my attic with red herrings. Works well, but smells a bit in summer.

May i ask why you chose Red Herrings as opposed to any other colour?

 

[John Brown]

May i ask why you chose Red Herrings as opposed to any other colour?

Yes, you may.
Unfortunately, I don't have a witty answer.

By the way, I have Drayton Wiser TRVs, which are, or were, a.bit cheaper. They seem to do the job, but the app/firmware is not perfect.

 

[Stevekane]

My quite old condensing boiler has that feature, but it's manual, sadly. I suppose I could automate it with a stepper motor to turn the control...

Or you could just turn the knob yourself when the weather turns colder, this morning I noticed that our boiler stat was turning the boiler off although the room stat was still calling for heat, so I turned the boiler stat up a little, this means the boiler is running for longer periods at a higher temp.
It seems to me that a problem is that were now in a situation where were having to use very complex multi faceted systems as outlined in a post above to extract the maximum economy, and of course with this complexity comes unreliability and many of the gas fitters barely understand them, so they advise customers to buy a new one, so any savings you might have made goes in another £3000 boiler! The real shame is that were still using wet central heating systems at all, clean electric with no servicing and when the heaters conk out you pop up to Argos and buy another for £29.99 and just plug it it!,,,if only electricity wasn't so bloody expensive!
Steve.

 

[John Brown]

Or you could just turn the knob yourself when the weather turns colder, this morning I noticed that our boiler stat was turning the boiler off although the room stat was still calling for heat, so I turned the boiler stat up a little, this means the boiler is running for longer periods at a higher temp.
It seems to me that a problem is that were now in a situation where were having to use very complex multi faceted systems as outlined in a post above to extract the maximum economy, and of course with this complexity comes unreliability and many of the gas fitters barely understand them, so they advise customers to buy a new one, so any savings you might have made goes in another £3000 boiler! The real shame is that were still using wet central heating systems at all, clean electric with no servicing and when the heaters conk out you pop up to Argos and buy another for £29.99 and just plug it it!,,,if only electricity wasn't so bloody expensive!
Steve.

If only we could dig electricity out of the ground!

 

[jimbowley]

Having access to an MCIS approved heat loss calculator I can confirm the net result of a substantially cooler internal space adjacent to a heated space is more energy being needed to heat the heated space.

I'm not sure what the net means there, but there's no way it takes more energy to heat space1 versus space1 plus space2. I have to assume you are seeing increased output from say radiator 1 and forgetting that previously there was also a radiator 2 which is now off. Or you've changed the system boundary.

The reason I'm confident in saying this is that it's a very simple system, the system boundary is all the external surfaces and the heat loss is proportional to the temp delta across those walls, the internal details don't matter beyond the resulting temperature on the inside of the external walls.


For the question of letting things cool fully or maintain some temperature, you have to run the models from the same starting conditions. That is start at 20deg, let the house cool to Xdeg and then heat it back up to 20deg. ie you can't start one model at 0deg and another at 10deg and then conclude that maintaining the house at 10deg uses less energy because it used less to warm it up to 20 in your (truncated) simulation.

Here's a thought experiment: if keeping the house at say 10deg overnight was more efficient than letting it fall to zero, then why isn't 11 better then 10, ...... and so on until you just leave it at 20 all day and night ?

PS. I don't mean to be having a go at you, but you have picked up a wrong idea somewhere and I'm happy to correct it. Once you see it, you'll be happier too so we'll all be happy

 

[leisurefix]

Not any easy thing to do when one considers that most domestic punters look at one thing and one thing only - the price. Most would be unwilling to pay for something that they feel they can learn from the internet for free.

There are also so many variables with each installation that a site visit would be necessary which would need to be paid for. Then there is the issue of liability if the system doesn't work 'as expected' (an useful get-out for the punter) and they end up telling porkies about how they used the system.

A good idea on paper but not in reality I fancy.

A few months ago I tried to find and employ a heating consultant (not an engineer who was going to install a system), I failed to find one. I am researching this myself now from whatever information (including forum posts!) I can find online.

 

[Spectric]

I don't want apps and clouds involved in my heating system because you are introducing levels of complexity that you really don't need. We did have three so called alexa power points but now all gone into the bin and gone back to simple digital timers that work, Alexa was so unreliable and lights would come on randomly at times or not on at all, complexity can work but not on the cheap.