Please help ASAP!! Do I need to bolt down an air compressor?

[buening]

Regarding breaker/wire size, what is the FLA stated on your electric motor? A good rule of thumb is size your breaker for 175% of the FLA (amps). For example, my 7.5hp is 32 FLA so my breaker in the disconnect box is 60A. I am running 6 ga wire to match the breaker size. With yours being a 5hp, it'd venture to guess it's around 17 a which would put you at a 30 A breaker. You may post this in the electrical forum to double check with the electricians on board. A 60A breaker with that size motor just doesn't seem right.

 

[ArthurPE]

Regarding breaker/wire size, what is the FLA stated on your electric motor? A good rule of thumb is size your breaker for 175% of the FLA (amps). For example, my 7.5hp is 32 FLA so my breaker in the disconnect box is 60A. I am running 6 ga wire to match the breaker size. With yours being a 5hp, it'd venture to guess it's around 17 a which would put you at a 30 A breaker. You may post this in the electrical forum to double check with the electricians on board. A 60A breaker with that size motor just doesn't seem right.

that's a pretty good rule of thumb...

his FLA ~ 21A
21A x 1.75 ~ 37A
I would use a 40A w/ #8
but a 30A with #10 would probably be fine

 

[up4speed]

This whole wiring thing had me stressing out and I was almost ready to cut the breaker down to a 30A, but I found this article that, if I'm reading it correctly, I think supports what the electrician, and Ingersoll Rand said. If you look at the first picture (Sec.430.22(a) of the electric code), it looks like they use a #10 wire with a 60A breaker on a similarly sized motor that I am using. I think the theory behind it is that because it's a motor (as opposed to a standard circuit), the motor has it's own thermal protection built in so it will trip if necessary, and the 60A breaker prevents a trip during the start-up spike. I guess if there is a direct short the 60A would blow before there is any damage to the #10 wire. It all works as a system as long as it's a dedicated line powering the motor. Take a look and tell me if you think I'm reading it correctly. I'm not trying to stir the pot here, I just want to get it right because I know that one of the worst thing you can do for motor longevity is to strain it during start-up. On the flip side, I obviously don't want a fire!!! see the attached link with info from the National Electric Code and tell me what you guys think?

http://ecmweb.com/nec/motor_calc/

Thanks again in advance

 

[bgott]

Will this help?

http://www.electrician2.com/calculators/motor_ver_1.html

 

[benjamming]

Details from my Champion air compressor manual...