Connecting relay switch to nest thermostat

[GeoffHusa]

I am installing an inline duct fan to boost airflow when AC or heat is running. I need to wire a relay switch into the thermostat wires so that relay switch is activated whenever the AC or the heat is turned on. Problem is that I don’t know which wire to put the relay switch on. Relay is a RIBU1C and I’m looking to wire the low voltage side of the relay to the nest wiring. Nest wiring harness has the 6 points; Y,C,W on left side, and G,R,*OB on right side. Wires used are Y=yellow wire, C=blue wire, G=green wire, R=red wire, *OB=white wire. Any help would be greatly appreciated!

[tajennifer]

Hi GeoffHusa,

Thank you so much for posting. I understand that you need to connect a relay switch so the inline duct turns on or off with the AC or heat. Based on the information that you shared about your system, this specific installation requires a Nest Pro technician. Don't worry; we are here to help. Here's how to locate technicians in your area who can help you with Google Nest products. You must deal with a qualified professional who works with Nest products. To request this, you contact our installation partner, Ontech. 
Please keep me updated. I'll be waiting for your response.

Best regards,
Jenny