24V smart thermostat

[ming666]

Hi
I have underfloor heating (water system) and I'd like to replace the room thermostat with a smart one (one of the cheap ones!)
However they all seem to be 95-240v and mine is 24V. It's a Wirsbo.
The Nest ones seem to be 24V but are 10 times the price.



Despite the great fat wires it's showing 24V (well 28 actually) on the multimeter.
Anyone help me out with what to get? is there a reason that the cheap ones don't come in 24V?

 

[ianmcd]

Most single channel timeswitches have Volt free switching, two channel programmers dont as they switch motorised valves, I think the 95-240V you are looking at is to actually power the units, and not the switching terminals

 

[ming666]

Most single channel timeswitches have Volt free switching, two channel programmers dont as they switch motorised valves, I think the 95-240V you are looking at is to actually power the units, and not the switching terminals

That did cross my mind. I have a 24V one here that I ordered. However the inputs on it clearly state 110-240V



It's not a timer (the old one) it's just a room stat.
I could try it and see what happens!
Anyone have any idea what the different coloured wires going to my stat represent?

 

[oldbutnotdead]

As @ianmcd , your new toy requires a supply of between 110v and 240v to power its innards.
The relay controlled by those innards makes or breaks a circuit between pins 1 and 2.
You may find that your new toy doesn't work very well with UFH (from what I've seen the operating band for UFH is much tighter than for conventional heating.
Without seeing some better pics of the back of the existing stat it is tricky to say what your existing wires do

 

[ianmcd]

That did cross my mind. I have a 24V one here that I ordered. However the inputs on it clearly state 110-240V

View attachment 208546

It's not a timer (the old one) it's just a room stat.
I could try it and see what happens!
Anyone have any idea what the different coloured wires going to my stat represent?

They dont represent anything never go with colours on a heating system

 

[endecotp]

The relay controlled by those innards makes or breaks a circuit between pins 1 and 2.

That’s not how I read that diagram!!!

I see a motorised valve which should be connected between 1 or 2 and neutral, with the assumed internal relay between live (4) and 1/2 normally closed/open respectively.

I could be wrong though. I’d open it up to check.

ming666, can you post a link to that device? I’m interested by the modbus connection - though it may be blanked off?

 

[ming666]

ming666, can you post a link to that device? I’m interested by the modbus connection - though it may be blanked off?

The 240V one?
Here https://smile.amazon.co.uk/gp/product/B083XHK8PW/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

 

[ming666]

They dont represent anything never go with colours on a heating system

Thanks!

 

[ming666]

As @ianmcd , your new toy requires a supply of between 110v and 240v to power its innards.
The relay controlled by those innards makes or breaks a circuit between pins 1 and 2.
You may find that your new toy doesn't work very well with UFH (from what I've seen the operating band for UFH is much tighter than for conventional heating.
Without seeing some better pics of the back of the existing stat it is tricky to say what your existing wires do

Well it won't work at all since it needs 240V and the wires I have are kicking out 24V! But I don't see how UFH can be any different from anything else, surely it's just a switch activated at a certain temp to open an actuator on the manifold? It hits 21C and closes the switch?

 

[oldbutnotdead]

That’s not how I read that diagram!!!

I see a motorised valve which should be connected between 1 or 2 and neutral, with the assumed internal relay between live (4) and 1/2 normally closed/open respectively.

I could be wrong though. I’d open it up to check.

ming666, can you post a link to that device? I’m interested by the modbus connection - though it may be blanked off?

Apologies- yes think you're correct with your reading of the back of that thing, served me right for looking at it on a phone with a cracked screen & erratic zoom.....odd toy, is it switching the neutral?

 

[bernardgreen]

But I don't see how UFH can be any different from anything else, surely it's just a switch activated at a certain temp to open an actuator on the manifold?

Comparing normal radiators heating the air in the room to UFH heating the room.

In UHF systems the thermal mass of the floor is much greater and the thermal conductivity of the floor is much lower. The heat from the thermal mass will continue heating the room after the water flow has stopped. This has to be considered when calculating when the under floor heating should be switched ON and OFF.

 

[ming666]

Comparing normal radiators heating the air in the room to UFH heating the room.

In UHF systems the thermal mass of the floor is much greater and the thermal conductivity of the floor is much lower. The heat from the thermal mass will continue heating the room after the water flow has stopped. This has to be considered when calculating when the under floor heating should be switched ON and OFF.

Thanks.
Are you saying that the thermostat that I have at the moment takes that into account?
Whenever I use it I can hear it click when I turn it past the current temperature and it doesn't seem to be doing any more than be an on/off switch.

 

[bernardgreen]

Are you saying that the thermostat that I have at the moment takes that into account?

I can't answer that as I do not know which thermostat your system has. Some thermostats controlling UFH will turn the heating OFF before the required air temperature is reached since the heat in the floor will continue heating the air for some significant time

 

[ming666]

I can't answer that as I do not know which thermostat your system has. Some thermostats controlling UFH will turn the heating OFF before the required air temperature is reached since the heat in the floor will continue heating the air for some significant time

Thanks
It is a wirsbo and it was installed with the system so I would assume that it is made to do that.
Some of the Chinese smart thermostats are flagged as being made for UFH so maybe they do the same. Unfortunately they are all 240v so I can't use them!

 

[ianmcd]

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