Tekmar 256 not connecting with nest

[Milissacarter]

I connected the nest thermostat wire to the Google power connector according to the wiring instructions red to red, white to white, and then the power connector to the tekmar256 common to common, red to red, white to thermostat. The nest has power and is on the wi-fi, however it isn’t triggering the furnace to turn on. Thoughts?

[Patrick_Caezza]

@Milissacarter 

Where are you located? In the USA/Canada or UK/Europe?

Boiler controllers can be a pain to connect to a Nest thermostat.

Do you have a picture of the original thermostat's wiring that you can post here?

[Milissacarter]

I am located in the US. I am not looking to replace the Tekmar 256, rather connect the Nest to it. I don’t have a picture of the original wiring. I only changed two wires, moving them from the Tekmar to the power connector and then connecting the power connector to the tekmar. Is used the online manual of the tekmar and the power adapter and still doesn’t work.

[Patrick_Caezza]

@Milissacarter 

You might not need the Power Connector.

Terminal 7 - T to W

Terminal 8 - R+ to R

Terminal 9 - C- to C 

[Milissacarter]

Thank you. I did try that and it worked, however the boiler didn’t turn off when I turned the thermostat down. And the Nest complained that I need the power adapter.

[Patrick_Caezza]

@Milissacarter 

That makes sense. The boiler can't provide enough power for the thermostat.

Did you get an external 24-vac transformer too?

[Milissacarter]

The google power converter is considered an external 24-vac transformer. When the power converter is connected the thermostat is powered, wifi connected, controlled at the device and wirelessly, however doesn't start the boiler when turned on.

[ovidioj]

Hello @Milissacarter, 

Thanks for posting in the community. 
I understand how frustrating it must be to have your Nest thermostat seemingly working perfectly—powered on, connected to Wi-Fi, and controllable—but not starting the boiler. Let's see if we can figure out why it's not communicating with your boiler properly. I would like to know some information about your HVAC system.

• Is this the first installation? 
• Do you get or see an error code on the display? 
• Do you have an idea or a picture of how the wires were installed? 

Please keep me posted. Thank you. 

Regards, 

Jorge