I'm looking to install an electric garage heater in my garage and I'm looking for some advice on the correct breaker size and correct wire gauge. The heater is a 7,500 watt and is uses 240 volts, the manufacture states that it draws 31.3 amps, requires a fuse of 45 amps and uses #8 copper wire. When I do the math on this, 7500 / 240 = 31.25 amps, code states that the breaker needs to be 125 percent larger than the circuit it's protecting(if it's continuously used for 3 or more hours) so 31.25 x 125 = 39.07 amps.

My question or concern is their 45 amp breaker recommendation vs what I calculated at 40. I already have #8 wire which is rated at 40 amps, if I go to a 45 amp breaker (if I can find one, as I can only find 40 & 50 now) I will need to increase my wire size from #8 to #6. The only other determination factor is the length of the wire run, which I figured up to be 85' which is very close, it could be a foot or two +/-.

Looking for recommendations, will I be okay with 40 amp breaker and #8 wire or do I need to step it up to 45-50 amp breaker and #6 wire.

Thanks