RC or RH wire?

[faithhicks1]

My old NEST thermostat had just an R wire. The new Learning NEST has a RH and RC. Which one do I use? My HVAC guy*  connected it to RC, but 15 minutes later the breaker tripped. Now he says it’s a coincidence and call an electrician. Please advise and I doubt it's a mere coincidence.

Also, when it was running for that fifteen minutes, I felt like I wasn’t very warm at 75 degrees (when 72 is usually just great. Maybe I was still trying to warm up from the cold house.)

Thanks.

*(Because originally we thought it was the HVAC when we have the NO POWER code on the original NEST thermostat, then a replacement NEST, then the new Learning one.)

[Markjosephp]

Hello faithhicks1,

Thanks for reaching out about the issues with your new Nest Learning Thermostat. The decision of whether to connect to the RH or RC terminal can depend on your HVAC system setup. Generally, RH is used for heating, and RC is used for cooling. However, in some systems, they can be bridged together. 

Given that your HVAC guy connected it to the RC terminal shortly after the breaker tripped, it might indicate an electrical issue. To isolate, could you share with us a photo of your old thermostat and Nest Thermostat's wiring setup? Also, gather the power readouts in the Technical Info settings and inspect for any wiring reports in the Equipment settings.

I'll look forward to your response.

Best regards,
Mark