Hey y'all. Been a while since I was here. Hope someone can un-confuse me.
Currently using #10 THWN, protected by a 20-amp breaker, for a run from the house to a residential greenhouse. I'm using the #10 in this case for Voltage drop. Once at the greenhouse, however, I was planning on switching to #12 THWN for branch circuit. My question is about derating the wire once it is inside the higher ambient temperature of the greenhouse. Assuming the temperature will be higher enough to warrant derating, would I have to derate to the point of having the circuit on a 15-amp circuit? If so, what are the ramifications, if any, of having my #10 on a 20-amp breaker?