Wiring W and R/RC only - electric heat

[ShineyG]

Hi. I just bought the Nest Thermostat. 

I have an electric base board heating system. Wires are W and R/RC

Will it work?

[ShineyG]

After some reading I connected the r and w wires and continued set up.  However it’s now telling me I need a c wire.  There is a black wire that looks like just a ground wire in the hole. It wasn’t connected to anything in the old system. Could this be a c?  If not, then I will get the adapter. 

[Jenelyn_O]

Hi ShineyG,

Thanks for checking it with us. To ensure that the spare wire you found is can be used to become your thermostat's common wire is to check your system's control board. Please take a photo of the wires connected to your system's control board and make sure that the labels of the wires are visible. Also, if you have a voltmeter, please use it to check how much power is in your black wire. 

Best,

Jenelyn