Meross MTS200 Install

[Stuckinarut]

I wonder why there’s a link in the room stat terminal at the boiler, but the old thermostat works?

 

[EFLImpudence]

I wonder why there’s a link in the room stat terminal at the boiler, but the old thermostat works?

The old one doesn't need it -

all it does is connect L to NO; the new one connects COM to NO so COM has to be connected to L.

 

[Stuckinarut]

The old one doesn't need it -

all it does is connect L to NO; the new one connects COM to NO so COM has to be connected to L.

Yeah I understand that at the thermostat end, I mentioned the boiler end. If you look at the photos, there’s a link in the room stat terminal, which on some models of boiler will call for heat all the time.

 

[EFLImpudence]

Yeah I understand that at the thermostat end, I mentioned the boiler end. If you look at the photos, there’s a link in the room stat terminal, which on some models of boiler will call for heat all the time.

That's not the room stat terminals; it is the hot water ones.

 

[Harry Bloomfield]

I wonder if the neutral, is not connected to anything at the other end of that cable? The original stat, appears to be a mechanical stat, so would appear to work without the neutral but the fancier, newer unit, being electronic, will need the neutral.

Another possibility, is that the OP has damaged the new stat., randomly connecting the wiring to it..

 

[EFLImpudence]

I wonder if the neutral, is not connected to anything at the other end of that cable?

D'oh that's it.

They grey is connected to 19.

 

[Stuckinarut]

That's not the room stat terminals; it is the hot water ones.

Looks like it says room stat to me, my bad

 

[EFLImpudence]

Looks like it says room stat to me, my bad

Oh. I was looking at the red link in 17 & 18. I think I had better give up.

 

[ericmark]

White, Brown, and black wires into a connector block so can safely test them, and use tester to see which are line, two likely faults, either White is not connected to neutral, or Black not Brown is feed.