Meross MTS200 thermostat help.

[fy29pz]

I recently purchased the Meross MTS200 smart thermostat.
It was to replace a Salus RT100 dial thermostat.

The Salus is connected with two wires as pictured.
Brown to COM
Blue to NO


I have attached the Brown to L on the Meross and Blue to N.
I have then used the supplied cable to bridge to the COM from L.

There is no power.
I thought it would be a swap out. I am no electrician but can turn power off and swap things around but it doesn't seem to be as easy as I thought.

I connected the Meross to a plug connecting the Brown to L and Blue to N from a kettle lead and it powered on.

Any help to get it working?

Any help would be great.

 

[CBW]

Your blue that is connected to NO is normally open as in switched live, NOT a neutral wire. You need a permanent live and permanent neutral, and some earth sleeving for the earth/CPC.

 

[fy29pz]

Hi Chris,

Thank you so much for the quick response and explanation.
I am a layman here. The sleeving for that earth I understand.
A permanent live and neutral, I assume is new cabling being installed? I assume not a novice fix?

Again, thanks for the advice.

 

[CBW]

Hi Chris,

Thank you so much for the quick response and explanation.
I am a layman here. The sleeving for that earth I understand.
A permanent live and neutral, I assume is new cabling being installed? I assume not a novice fix?

Again, thanks for the advice.

Yes would need additional cabling, could be a novice fix, however you'd have to run it from the fcu (spur) to the new thermostat, probably surface mounted. Could swap the new smart thermostat for a battery operated one such as the Nest E?

 

[leony]

Hi,

I have more or less the same question. My current thermostat is a battery operated one and would like to change to Meross thermostat. The current cable seems to be a twin & earth (3 core) but the thermostat uses the brown and blue only. My question is, can the 3rd non used copper be used as a neutral and connected directly to my Vaillant boiler (if possible) or if not, to a spur near the boiler and be fed to Meross in the living room?

I asked Meross and they said that their thermostat is not suitable for Vaillant, nor my cabling. I have found their answer a bit odd.

Please see the attached files, my current thermostat front & back, the boiler connection and the Meross MTS200 diagram.

 

[EFLImpudence]

My question is, can the 3rd non used copper be used as a neutral

No.

 

[Mister Banks]

Ignore the existing cable colours, you need to add a permanent live and neutral.

 

[leony]

Ignore the existing cable colours, you need to add a permanent live and neutral.

Thank you, I don't think adding another cable here is feasible, can you kindly advise if I can add a Nest thermostat to this set up? (Not the battery operated one). I believe Nest has a device called heat link which I can get it installed next to my boiler and I can arrange extra power if needed to this device, however the thermostat itself needs to be in the living room and this is the only cable (twin & earth) can be fed to Nest thermostat.

 

[EFLImpudence]

You cannot use anything that requires a mains supply AND a wire to send the signal.

 

[CBW]

Thank you, I don't think adding another cable here is feasible, can you kindly advise if I can add a Nest thermostat to this set up? (Not the battery operated one). I believe Nest has a device called heat link which I can get it installed next to my boiler and I can arrange extra power if needed to this device, however the thermostat itself needs to be in the living room and this is the only cable (twin & earth) can be fed to Nest thermostat.

Yes you could add a nest, the existing wiring might even be able to be used to power the thermostat from the heat link, depends on sporious voltage. The cable which is being used currently isn't correct either as it's not really heat resistant. You'd need someone in too as the cover forms part of the combustion circuit and needs checking for safety afterwards.

Can I ask what is wrong with the existing thermostat? Seems odd to swap an on/off for another on/off.

 

[ericmark]

As @CBW says, seems odd to swap and on/off for an on/off without some extra options, the extra options may be ability to turn on heating before starting from work to home, and I have tried geofencing myself, and found my boiler and system simply not big enough to be able to switch off, then latter allow it to reheat the home, it can maintain the home, but not reheat.

As said the Nest e will work with battery power and has geofencing, but I am using Nest Gen 3 and looking at changing it for a thermostat which will link to TRV heads.

Not all boilers use 230 volt for control, there are even although now rare as the popular was discontinued so 24 volt motorised valves, so step one is find out what the thermostat switches, is it low voltage or extra low voltage, note in the USA they call what we in rest of the world call extra low voltage i.e. under 50 volt, low voltage, so anything designed for USA is likely incorrectly marked.

In theroy each room is controlled by the TRV and by installing electronic heads we can in theroy control each room independently with it's own schedule, however myself I am having problems, as for the TRV to work, clearly the boiler must be running, however when the house is warm, we want to turn off the boiler, rather than leave it cycling off/on all the time.

Ideal every TRV would connect to a central hub which would in turn tell the boiler what to do, however I am finding theroy and practice don't always work, my carpet fitters smashed one of my TRV heads, so it was replaced, I left it on fire place, and noted there can be 4ºC warmer on fire place at 4 foot from floor level to next to radiator at 6" from floor, but my living room has two radiators 90º to each other so the placement of wall thermostats in relationship to radiators does not work.

But my main problem is the daft Nest Gen 3 thermostat does not connect to the TRV heads, and I would say pointless fitting any wall thermostat which will not connect to the TRV heads, Nest said it would, but seems when Google took over Nest the option was dropped.

I am now considering fitting Drayton Wiser at over £200 because Nest simply does not work, unless connected to the TRV heads can't see how it will work.

 

[leony]

Yes you could add a nest, the existing wiring might even be able to be used to power the thermostat from the heat link, depends on sporious voltage. The cable which is being used currently isn't correct either as it's not really heat resistant. You'd need someone in too as the cover forms part of the combustion circuit and needs checking for safety afterwards.

Can I ask what is wrong with the existing thermostat? Seems odd to swap an on/off for another on/off.

I am most of the time away from the property and need a remote solution to turn on and off the heating. I already use Meross brand and quite happy with it that is why it would be my 1st choice. If that does not work, I already have a Nest thermostat that bought recently at a very cheap price and was planning to use it somewhere else but no worries.

Can you please advise further on this? I will get a professional person to fit Nest and they can use the existing cable?

The cable which is being used currently isn't correct either as it's not really heat resistant. You'd need someone in too as the cover forms part of the combustion circuit and needs checking for safety afterwards

 

[CBW]

The cable is twin and earth, and is only heat resistant to a certain temperature. Heat resistant flex cable is in the region of approx 95 degrees Celsius, so able to withstand bing near the heat from the boiler. They could use the existing cable where it enters the boiler and pull back through, providing it doesn’t cause sporious voltage.