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#1877167
OK - thanks. But in my single room example, if the TRV is set to 22˚C and the Smart Thermostat is set to 26˚C, would I be right to assume that the radiator will turn off when it "senses" 22˚C but the boiler will continue to run as the Thermostat never senses 26˚C ? And vice versa if the TRV is set to a higher temp than the Thermostat?

If so, and if I am happy to tweak the TRV settings to obtain a comfortable environment, then I can see that I will not need the Thermostat at all.
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By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1877220
The "smart thermostat" on my Hive system is effectively the controller. It's that which holds all the schedules, overrides, holiday times, and communicates such with the app. It has heating and temperature times, hot water times, can be driven with IFTTT, can control lights and/or sockets, have door or PIR sensors, etc.
By riverrock
FLYER Club Member  FLYER Club Member
#1877294
@Paul_Sengupta on hive there is the thermostat, receiver (connected to your boiler), then also a separate hub (which connects to your broadband). It's that hub communicates with lights. At least on my version 1 thermostat it is anyway.

Normal advice is to have one radiator without a TRV on it (likely a central location representitive of the house, like a hallway), and have the smart thermostat within the space heated by that radiator. That thermostat allows control of schedules, and for "ready by" functionality (you set what time you want house to be heated by, rather than the time you want the boiler to fire), and the system bases that lead time on the smart thermostat.
For hive that thermostat is required - I don't know about Tado.

Do you want a way to control your system when the internet dies?
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By stevelup
FLYER Club Member  FLYER Club Member
#1877326
Colonel Panic wrote:OK - thanks. But in my single room example, if the TRV is set to 22˚C and the Smart Thermostat is set to 26˚C, would I be right to assume that the radiator will turn off when it "senses" 22˚C but the boiler will continue to run as the Thermostat never senses 26˚C ? And vice versa if the TRV is set to a higher temp than the Thermostat?

If so, and if I am happy to tweak the TRV settings to obtain a comfortable environment, then I can see that I will not need the Thermostat at all.


I don't think it's actually a practical consideration - was just suggesting a reason. As you know, I have Honeywell EvoHome here. Except for the main kitchen/diner/study which has UFH, every other room has the Honeywell TRVs.

The temperature readings off the system are very accurate - I don't get a different reading in the room than the one the system shows. I guess because the TRVs are located at the bottom of the rads, they're picking up the 'incoming' ambient air rather than being affected by the rad itself.

But yes, if your TRV is closing before your room stat detects the room is warm enough, it's never going to shut off.

In the 'olden days' before everything got smart, the rule of thumb was to -not- have any TRVs in the room that your main stat was in, for very obvious reasons. You want one or the other.
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By rikur_
FLYER Club Member  FLYER Club Member
#1877329
Colonel Panic wrote:OK - thanks. But in my single room example, if the TRV is set to 22˚C and the Smart Thermostat is set to 26˚C, would I be right to assume that the radiator will turn off when it "senses" 22˚C but the boiler will continue to run as the Thermostat never senses 26˚C ? And vice versa if the TRV is set to a higher temp than the Thermostat?

If so, and if I am happy to tweak the TRV settings to obtain a comfortable environment, then I can see that I will not need the Thermostat at all.

I think you're right.
In a non-smart set-up, both the room thermostat and the TRV both have to be 'cold' to heat the room (wall stat to activate the boiler, TRV to let the water through).
I thought smart systems generally worked on the basis of a call for heat from the room thermostat or the TRV..,. but it would only get to the radiator if the TRV was 'cold'. So whilst either can wake the boiler, only the TRV being 'cold' can heat the room in question.
Feels like this set-up creates a problem - i.e. when the TRV thinks it is warm enough, but wall stat is cold, then boiler just runs and runs via whatever bypass radiator you have elsewhere.

As an aside, our aircon cassette units both have two sensors per room - one on the wall control, and one on the air intake to the cassette unit, but they're designed to take two readings, prioritise, guess what to do next, etc. They're certainly more stable than the aircon wall units which only sense on the air intake and can be a bit prone to thinking the room is hotter than it is, as they're drawing in air at ceiling level.
#1877392
“Smart” heating systems are as smart - or dumb - as the inputs/outputs and programming dictate.

Systems like Tado clearly state that best comfort will be obtained from a room stat that is in the “golden spot”…which is never going to be attached to a radiator.

Thing is, said smart TRV have temperature (and humidity) sensors that take readings every minute or so - and smarts like “open window detection”, which a dumb TRV can never have.

The overall system should be tuned to meet comfort levels and timings by room - which is something classic systems and the likes of Nest can’t do, simply because every single radiator within a per-room smart thermostat/TRV system like Tado can call for the boiler to start. If one room needs a sudden boost, all other TRV close and just that one room gets the boiler for itself.
By riverrock
FLYER Club Member  FLYER Club Member
#1877407
Gas boilers have a minimum output, so to hear one radiator they will have to constantly cycle on and off. They also need a large temperature differential between flow and return to allow condensation, improving efficiency from the 70ish percent to 90ish.

Is just heating one radiator with a gas boiler a false economy?
#1877420
Thanks all - you have in many ways confirmed my suspicion that the Smart Thermostat is not doing anything of benefit in my situation. But rather than take the batteries out & risk confusing the system I will just set it to FrostSave 24/7.

I do have one radiator without a TRV, so I am following best practise there. And not sure if the false economy comment was meant for me, but @riverrock my one room / one radiator example was just that, an example; my oil fired boiler heats all rooms and I have 20 Tado TRVs (£££) ...
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By rikur_
FLYER Club Member  FLYER Club Member
#1877423
riverrock wrote:Is just heating one radiator with a gas boiler a false economy?

Probably, even more likely with an oil boiler.
Most gas/oil boilers only get anywhere near their stated efficiency if working flat out, but the majority of the time are being used to take the chill off the house, or maintain it at temperature. I suspect most people are completely unaware of how inefficient their heating systems are in real world circumstances.
Air-source is the opposite, least efficient when working flat out, but most efficient when ticking over.
OCB wrote:Systems like Tado clearly state that best comfort will be obtained from a room stat that is in the “golden spot”…which is never going to be attached to a radiator.

Excuse my ignorance, but is Tado smart enough to understand the room stat and TRV are in the same room? In which case I can see a benefit. My experience has been limited to Hive which treats them independently regardless.
#1877429
rikur_ wrote:Excuse my ignorance, but is Tado smart enough to understand the room stat and TRV are in the same room? In which case I can see a benefit. My experience has been limited to Hive which treats them independently regardless.

The Tado Smart Thermostat can be allocated its own "room", or included within one of the rooms with TRVs; I can't recall why, but when I set my system up I created a specific room for the Thermostat within the software, but physically keep it in the Hall (which also has x2 TRVs).
#1881417
Quick update:

Removal of old thermostat and putting Tado in place + confirmed working: 45 minutes.

The only confusion for me was that the wiring was blue, brown, yellow and green...and they didn't marry up to what I thought should be the right assignment. After a bit of searching, it was clear that whoever fitted the system just threw it in willy-nilly, and the controller is working off 36v rather than 240v.

TBH - it is bliddy impressive that Tado have done the decent thing and have installation instructions for the majority of the European install base, including the 15+ yr old Junkers wired thermostat that I had until a few hours ago.

Actually - really impressive - their instructions gave me a terminal block level diagram, as it was part of the personalised installation instructions. The only thing I could ask for is augmented reality, but I'm greedy ;)