I couldn't wait for an answer and hooked it up. There was a Y, C, G, RC with a jumper to RH, and an OB wire in the BCC100 thermostat mounting bracket. After resetting my Nest, which I needed to do as I have new/diff furnace, Nest Setup asked if the OB connection was used for an O or B wire. I had no idea and chose O which was recommended if you have no idea. That was incorrect as when testing HEAT operation my house was cooling. Nest setup tells you if that happens to designate the wire as a B wire (or opposite of what you chose). That fixed it for heat mode at least. Haven't tested cooling or heat/cooling modes yet.
It is worth noting that it gave me a setup error saying it could not detect the Y wire. I reseated the wire in the mounting bracket terminal and finished setup without issue. I've read in other posts that sometimes an undetected Y wire may just be a false error, that Nest needs to take care this, but that it does not impact operation.
