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- Jun 12, 2014
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Electrical code specifies the minimum breaker size of 125% x FLA which puts you at 45A and you would round up to a 50A breaker would be the minimum size breaker and many posts recommend 60A. Your capacitors are well withing spec. which is normally has much more variability (+/- variance). My guess is that the breaker was marginal to start with and they can get a bit finicky with time. As far as wire size, on a 50A breaker I use #8 to my compressor, with a 7.5Hp I am a bit surprised at the use of #8. It also depends on the temp rating of the wire, if pulled through conduit vs. plug, etc. Leave that to the electricians. I will say that a 40A breaker is too small for the motor rating, panel breakers tend to be inexpensive, so could try a 50A with the #8 wire you have. I have a Champion 2-stage HR5-8 compressor which my manual specifies #8 wire for 5Hp single phase, #6 wire for 7.5Hp single phase model, and for longer runs #4. They do not give a breaker size, but it must be upsized to handle a motor start load and with your SFA of 1.15 you could be pulling over 40A as it gets to higher pressures.