"Smart" central heating systems

R.C.Anderson

R.C.Anderson

R.C.Anderson

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20 Feb 2009
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Ashton-Under-Lyne
Moving to a new property in the coming months & want to add in better central heating control than the TRVs that are there currently.

My wishes:
  • Retrofit without too much work (e.g. actuator valves on radiator, rather than manifold actuators)
  • Invidivual room temperature & time control
  • Integration to home assistant if possible
  • Temperatures set by a real temp, rather than an arbitary number (e.g. 21C, rather than "3 warm")
  • Include boiler control for when any room needs heat
  • ability to control the heating of a hot water cylinder
  • Easy to use control, both locally & remotely
Anyone got any systems they'd recommend & anything other people find is useful to have?
 
Tado or Wiser, after trying them both they each have their idiosyncrasies but the wiser scheduling system still works if you have no internet whereas the tado scheduling is online, so you have to turn on the heating and hot water via the smart thermostat. Tado do have a new system called X coming in the autumn for UK systems though and might be better.
 
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Tado can do all of those but not sure about home assistant.

Wkth regard to "easy to control" the tado is fine but if you have 10 valves like mine it's a bit more nuanced than a standard system. So to a degree less valves would keep any system simpler.
 
I have Tado, only faulty bit about it is that valves measure the temperature.....ideally there should be temp sensor that's in the middle of the room instead of right next to the radiator.
 
oggiet said:
I have Tado, only faulty bit about it is that valves measure the temperature.....ideally there should be temp sensor that's in the middle of the room instead of right next to the radiator.
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Actually you can place one of their wireless smart thermostats in the same room, make it the measuring device in that room and it will control the smart rad thermostat(s). I have this setup controlling the two radiators in our lounge and it seems to work better.
 
cuke2u said:
Actually you can place one of their wireless smart thermostats in the same room, make it the measuring device in that room and it will control the smart rad thermostat(s). I have this setup controlling the two radiators in our lounge and it seems to work better.
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Yeap I've got that downstairs as well. It's in bedrooms that it's a pain with the valves.
When we move I will look getting it all redone without Tado. Hopefully can find some tvrs that can work well with home assistant and some sensors that can be placed away from radiators.
It's a can of worms I'm not looking forward to opening :D
 
I put smart trvs predominantly in rooms I didn't want hot (to lock them off when not used) and rooms that were sensitive to being too cold (E.g. nursery). The remaining rooms are on regular trvs set to fully open. If you start to mess around too much and heat individual rooms your boiler will hate you and your consumption and cost will increase because it isn't reaching an efficiency state/condensing.
 
oggiet said:
Yeap I've got that downstairs as well. It's in bedrooms that it's a pain with the valves.
When we move I will look getting it all redone without Tado. Hopefully can find some tvrs that can work well with home assistant and some sensors that can be placed away from radiators.
It's a can of worms I'm not looking forward to opening :D
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I've already given you the suggestion for using a smart temperature sensor you can place anywhere in the room using it in conjunction with their smart radiator sensor, so I'm confused as to why you think it can't be done. It's no can of worms plus tado works with alexa, smartthings and Google home assistant.
 
cuke2u said:
I've already given you the suggestion for using a smart temperature sensor you can place anywhere in the room using it in conjunction with their smart radiator sensor, so I'm confused as to why you think it can't be done. It's no can of worms plus tado works with alexa, smartthings and Google home assistant.
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I know you can, I just don't want to pay another £80 for each room on top of smart tvrs. Unless other smart temp sensors can be used.
 
I've got these Sonoff TRV's on every radiator, the boiler is a Vailant something-or-other (I forget the term, it's not a combi, there's a hot water cylinder) controlled by a Nest Thermostat.

When any of the TRV's call for heat, Home Assistant will trigger the boiler and then turn it off when there's no further call for heat. I don't do anything in the Nest app, everything is done through Home Assistant automations.

Generally the TRV's in the unoccupied areas of the house are set fairly low but if we've got guests staying I'll turn up the TRV's in the guest room and guest bathroom. I'm planning to try and automate that by having Home Assistant read a calendar.

Getting the hot water controlled by Home Assistant was a bit of a faff, Google don't expose that as an option in the Home Assistant integration so I'm using Home Bridge with this plugin.

I don't know that I'd necessarily recommend this setup. It works great but being reliant on Home Assistant behaving doesn't get wife approval on the very odd occasion it has a brain fart and something doesn't work.
 
I would look to see if you can get some better controls for your boiler before spending a load on smart TRV's.

If your boiler is capable of weather compensation (outside temperature sensor needed), setting up the controls properly will save you a bunch of cash.
 
b0rn2sk8 said:
I would look to see if you can get some better controls for your boiler before spending a load on smart TRV's.

If your boiler is capable of weather compensation (outside temperature sensor needed), setting up the controls properly will save you a bunch of cash.
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What benefits does this provide? At the end of the day, if I want a room at 20C, then it needs to heat until it is, and this may take longer if it's cold outside, but I can't think how anything would save money by knowing how cold it actually is outside?
 
It’s because of how boilers work, they use a lot of energy when starting up before they get into their condensing modes (if they even get into them, most don’t most of the time).

The purpose of the outside temperature sensor is to give the boiler the ability to modulate its output based on the required heating need to maintain a steady state temperature. This is called wether compensation.

The bigger the temperature difference between the outside air and your inside temperature, the more heat is lost from the property. So the warmer it is outside, the lower temperature you can run your water through your radiators to maintain your target temperature, say 20C. The lower temperature you run the water through your radiators, the less gas your boiler uses.

The purpose is to allow the boiler to keep running at a low level in its most efficient mode rather than continuously cycling (on, off, on, off, on, off etc.) which uses a ton of energy.
 
b0rn2sk8 said:
It’s because of how boilers work, they use a lot of energy when starting up before they get into their condensing modes (if they even get into them, most don’t most of the time).

The purpose of the outside temperature sensor is to give the boiler the ability to modulate its output based on the required heating need to maintain a steady state temperature. This is called wether compensation.

The bigger the temperature difference between the outside air and your inside temperature, the more heat is lost from the property. So the warmer it is outside, the lower temperature you can run your water through your radiators to maintain your target temperature, say 20C. The lower temperature you run the water through your radiators, the less gas your boiler uses.

The purpose is to allow the boiler to keep running at a low level in its most efficient mode rather than continuously cycling (on, off, on, off, on, off etc.) which uses a ton of energy.
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Just had a quick look, it's very interesting and correct what you are saying. Apparently Tado will override control of flow temp even if there is outside temp reader..... automatically runs it at highest flow temp.

When we move we will need new boiler, might get heating specials to come and do our installation. Learn something new every day though, thank you.
 
TBH sounds like external temperature control isn't actually that important here as you're mearly guessing how much of an effect that has on everything else, and more you just need the system to be able to detect the room is upto temperature, and reduce the amount of heat into that radiator to the point it stabilises, and use some sort of PID algorithm to determine how much heat is requied in the room to keep the temperature stable. This would be best done on a room by room basis (do variable position smart TRVs exist (i.e. that aren't on/off, but can be 10% open, 50% open etc)?) Then if the whole system is upto temp, reduce the boiler flow temp until the room needing the most heat is at 90% open TRV for example.

If everything in the system is perfectly calculated (room insulation, other sources of heat, thermal mass etc), then knowing the external temperature could allow a better prediction, but without these other elements, I don't see how it's doing anything more than "it's colder outside today, lets pump an arbitary amount more heat around" This would also need either all rooms to be similarly controlled & need similar heat demands, or it wouldn't work anyway & you'd end up with a room that doesn't heatup properly, because another room is already warm enough & the flow temp has been reduced to prevent that room from overheating.
 
It’s actually very important and should be a feature of all modern heating systems regardless of heat source (gas, oil, heat pump etc.)

The emitter (radiator, underfloor heat) should be sized relative to the heat loss of the room and the house in total. While it might not be spot on, it should be in the ball park.

The other thing to consider is that closing off radiators in individual rooms doesn’t take them out of the thermal envelope of the house. Heat (a lot of it if internal walls, ceilings and doors are not very well insulated/sealed) will leak into to those rooms from the rooms you are still heating. Your remaining radiators are not sized to cope with this additional heat loss for the rooms they are in. This means you need to run the boiler at a higher flow temperature than you would otherwise need to maintain the target temperature. This can be less efficient.

The reason why you want to know the outside temperature is so you can vary the flow temperature down automatically if the heat demand is lower which makes it more efficient. If it’s 10C outside, you simply don’t need as much heat being put into the system than if it’s -5C outside.

You don’t need to have everything perfectly calculated. Even a proper heat loss calculations are based on a lot of assumptions. The modulation levels of the boiler are controlled by a configurable wether compensation curve. A heat loss calculation gets you in the ball park, you’d then tweak it as needed. E.g. if it’s overshooting, you’d drop the curve a bit.

There is a reason as to why all new heating systems have to be designed to operate at lower flow temperatures, it is just more efficient. Your boiler constantly cycling on and of and on and off is literally the last thing you want if you care about efficiency, the way you prevent that is varying the flow temperature based on the outside temperature.
 
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