I've installed 6awg copper wire to a junction box for a future electric garage heater. The heater will eventually hang from the ceiling approximately 4-6 feet in front of the junction box. (See photo below) This is on a 60 amp 240v breaker. Initially I was planning to install a 10,000 watt heater. However, I now plan to downsize the heater to 7500 watts. I realize I'll need to downsize the breaker to 40 amps. Two questions:
1). Is it safe to use the existing 6 awg copper with a 40 amp breaker assuming a 7500 watt heater?
2). Considering the above described downsize, is it safe to run an 8 awg appliance whip from the junction box to the heater? Thank you.