Nest Thermostat E Installation

[Davidcannon89]

Hi Guys,

I'm trying to install a Nest Thermostat E and I'm stuck at the wiring when it comes to replacing the thermostat (Myson Mrt1) with the Nest Heat link.

I've attached the wiring diagram from the existing thermostat, a photo of that wiring in situ, and the connections on the new heat link. Apparently I need to find "common" and "normally open" according to the app, but I've no idea how to find them.

Any help would be appreciated!

 

[stem]

Brown wire in Mrt1 terminal 1 goes to Nest-e 'C'

Black wire in Mrt1 terminal 3 goes to Nest-e 'NO'

The grey neutral wire in Mrt1 terminal 4 is not required. Isolate / insulate it and tuck it out of the way so that it doesn't touch anything. Under no circumstances connect it to the Nest-e

If you have a timeswitch / programmer that is currently controlling the central heating on/off times. That will need to be set to have the heating permanently 'on' 24/7. Otherwise it will interfere with the operation of the Nest.

 

[Davidcannon89]

Brown wire in Mrt1 terminal 1 goes to Nest-e 'C'

Black wire in Mrt1 terminal 3 goes to Nest-e 'NO'

The grey neutral wire in Mrt1 terminal 4 is not required. Isolate / insulate it and tuck it out of the way so that it doesn't touch anything. Under no circumstances connect it to the Nest-e

If you have a timeswitch / programmer that is currently controlling the central heating on/off times. That will need to be set to have the heating permanently 'on' 24/7

Hi,

Thanks for the reply. There's a second black wire connected to terminal 3 and also a red wire hiding behind the back which I won't know where it goes until I take the back plate off. I've attached a close up pic of this.

Would both wires in terminal 3 be connected to 'NO' on the Nest?

Should I isolate all additional wires?

Appreciate the help.

 

[stem]

I can only see one black wire under the terminal 3 clamp. If you are referring to the one above the screw at the top, that's part of the thermostat, which you will be removing.

The red wire isn't needed for the thermostat otherwise it would be connected to the existing one, so should be left alone. When you have revealed it, if you have any concerns or questions about it post back.

 

[Davidcannon89]

I can only see one black wire under the terminal 3 clamp. If you are referring to the one above the screw at the top, that's part of the thermostat, which you will be removing.

View attachment 180865

The red wire isn't needed for the thermostat otherwise it would be connected to the existing one, so should be left alone. When you have revealed it, if you have any concerns or questions about it post back.

Thanks mate, I'll wait until tomorrow morning to do it so its light. I'll give it a go after shutting the power off and report back.

Enjoy your Saturday night!

 

[Davidcannon89]

Hi,

Just to update, I went through this earlier today - your instructions of T1 to C and T3 to NO were spot on

The heating appears to be responding and the house hasn't went on fire yet, so I think we're all good!

Many thanks - appreciate the help.

 

[stem]

Great! Thanks for the update, it helps anyone else who finds this thread and wants to do the same thing.