how do i replace a tekmar 256 controller with a NEST - hot water system with weill mcclain boiler

[ulall]

I have a single zone hot water heating system fired by a  weill mcclain gas fired boiler with a pump

The controller is a Tekmar 256 with outdoor sensor. It seems to have a R T and C wires labelled and the others are just for sensors

The wiring manual for the Tekmar has this picture

https://www.manualslib.com/manual/1713395/Watts-Tekmar-256.html

How do i put the nest here?

[Jake]

Hey ulall,

Sorry for the late reply. I wanted to follow up and ensure you are good to go. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further. 

Best regards,
Jake

[ulall]

yes - still curious as to teh best way to do this

[Jake]

Hey ulall,

Reviewing the post and wiring diagram you had sent, I would recommend having a Nest Pro come out and take a closer look. Each system can be a little different, and it's best to have someone in person to review and ensure the device is set up correctly. I understand that this is not the most ideal answer, but I would not want to cause damage to your system if something is installed incorrectly. 

Best regards,

Jake

[Jake]

Hey ulall,

Please let me know if have any other questions from here, as I will be locking the thread in 24 hours due to inactivity. 

Best regards,
Jake

[Jake]

Hey ulall,

It has been a few days since the last reply, and I am going to lock the thread at this time. If you have any questions, please feel free to create a new post. 

Best regards,
Jake