Identify wires with no labels.

[Kram2]

I'm looking to replace an old controller that died on me. I'm hoping to use a nest as a replacement. The wires I have are both white and one has a red stripe. Nothing else to identify them with. It's a 24v system. I know one of the supplies power. When looking at the compatibility chart, I have know idea how I can know which wires I have in order to check the compatibility. 

[virnab]

Hi Kram2,

Thanks for reaching out to our community.

I appreciate you letting us know that you want to replace your old controller with a Nest thermostat. Thank you for providing us information about your previous installation and asking how to connect the wires you have in order to check the compatibility. No worries, help is here.

Usually, the Nest thermostat is installed in the same way that the prior thermostat was installed, but in order to provide you with more accurate assistance, I would require the following information:

• Could you please share a picture of the old controller and the furnace control board where the wires are connected?
• What is the type and model of your HVAC system?

Thanks for your kind attention; I will be looking forward to your answer.

Best regards,

Virna