Replacing Tekmar 908 radiant thermostat with Nest thermostat (Not learniing)

[kk2787]

Hi,

I was told I could replace Tekmar 908 radiant thermostat with a Nest Thermostat but having a great difficulties.  Google help desk gave me various different information, e.g., incompatible, new wiring, power connector, etc.  

The Tekmar has 6 wires, C. R, Rh, W, and two wires for sensor (noted No Power):  C is connected to C on the  transformer and R to R on transformer at the boiler.   And Rh and W on the thermostat are connected to R and W on the relay switch, respectively.  I suppose the temperature sensor is buried in the floor.   I have a conflicting info from web that Nest thermostat is incompatible  or need power connector (which I bought).   Any advice is appreciated.  Thank you.

p.s.. I had no problem with three other google nest thermostats.

[zoeuvre]

Hi kk2787, 

Thanks for posting here in the Community forum and for showing interest in our Nest Thermostats. Could you send us a photo of your current thermostat wiring configuration so I can take a closer look? 

Keep us posted.

Best,

Zoe

[kk2787 · Accepted solution]

[kk2787]

Thank you very much for your interest.  

Kevin

[zoeuvre]

Hi there, 

Thanks for getting back to us. Non-standard labels of 1, 2, 3, 4, 5 and 6 which means that your system is proprietary. Proprietary systems aren’t compatible with Google Nest Thermostats. However, some proprietary systems can be rewired by a pro installer to be compatible.

Regards,

Zoe

[kk2787]

I purchased Nest thermostat  after Google Tech support's assuarance that it would work.  Any other recommendation without rewiring by Google pro?  There are numeric labels but there are also corresponding conventional alpha labels, such as C, R, Rh, W.  And advice is appreciated.

[zoeuvre]

Hi there, 

Thanks for getting back to us, and I'm sorry for the late response. If you have already consulted Google Tech support and they have assured you that the Nest Thermostat is compatible with your HVAC system, it's worth following their recommendations. And if following the corresponding conventional alpha labels in your control board, then your thermostat wires are compatible with Nest Learning Thermostat 3rd generation only and should be wired to the Nest Learning Thermostat base as shown:

• (3) B wire to C on the Nest Learning Thermostat
• (4) G wire to G on the Nest Learning Thermostat
• (5) R wire to RC on the Nest Learning Thermostat
• (6) W wire to W1 on the Nest Learning Thermostat
• (1) W wire to W2 on the Nest Learning Thermostat
• (2) R wire to RH on the Nest Learning Thermostat

Also, here's a guide for the installation and setup of a Nest Learning Thermostat. 

Let us know how it goes.

Best,

Zoe