Originally Posted By: jhellwig
Originally Posted By: JHZR2
Originally Posted By: Donald
The wiring is #10.
I think there is too much vibration for solid wire.
From the air pressure switch is rubber service cord and a plug.
My question was about from the motor to air pressure switch. It's maybe 20" of wire.
The connector at the motor is made for a ring terminal or spade terminal. Not a lot of room either.
Near the compressor is a 100 amp sub panel with 20 amp @ 110v, 20 amp @ 220v, 30 amp @ 220v, and 50 amp @ 220v.
So if im reading this right, youre all set for the main wiring back to the panel. Im surprised that the other smaller jumper wasnt factory wired.
For that jumper Id definitely want 90 or 105C rated wire, gauge actually matters less because theres no practical length to drive a voltage drop. Assuming a 90% efficient motor, the load is around 17A, so you can probably get away with 12ga for that jumper, though 10 is better.
Id just go to HD and buy a few feet of SOOW 10ga cable for this. Its 600V rated, has 90C insulation, and is oil resistsnt which i like around oiled compressors. Make sure you have a good crimper, and terminate appropriately.
No. Insulation tempature is of no concern here. Wire gauge matters. Your amps for the motor are incorrect. There is no need for flexible cord.
Posting a picture of the nameplate of the unit would help determine what is needed. Without that all I can do is guess. I would say 10 gauge wire is correct assuming it is a somewhat normal motor but compressors have odd motors some times. Stranded wire in a flexible conduit would be the way I would hook it up for a customer. Much cheaper than flexible cord. That being said, if it had made it this long on solid wire there is no need to mess with it.
OK, let's review.
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No. Insulation tempature is of no concern here.
Really? So NEC Article 430 does not apply? That would say to select ampacity and a conductor rated based upon 75C values. So 90C is a meaningful and useful derating.
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Wire gauge matters.
Of course. But one selects wire size based upon ampacity for a given temperature rating. Voltage drop is a function of conductor length too, so that does come into play.
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Your amps for the motor are incorrect.
OK, how so? OP said 5hp 230V motor.
Convert 5 hp to kw: 3.73kW.
Assume 90% efficiency... Then its roughly 4.14kW.
4140W / 230V = 18A
I said "around 17A", so perhaps I was one off, but it may also be lower based upon motor efficiency. Of course, if 0.8PF is assumed, the wire may be a little small, if 12ga... But I never said that 10ga was wrong.
Tables show 20A to be fine for 12ga.
http://www.cerrowire.com/ampacity-charts
Even for SOOW, which was my initial thought.
http://www.cmewire.com/catalog/sec19-fcx/fcx-cu-01-amp.pdf
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There is no need for flexible cord.
Generally I agree. That said, SOOW, which is oil resistant flexible conductor, readily bought by the foot at any box store, is easy to work with and manipulate. If oil is spilled on it when servicing the compressor, no problems. Note I asked:
Originally Posted By: JHZR2
How do you know this is the case?
What do the terminals on the compressor look like?
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I would say 10 gauge wire is correct assuming it is a somewhat normal motor but compressors have odd motors some times.
Agreed. That said, Ive seen short runs in compressors factory wired with smaller gauge.
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Stranded wire in a flexible conduit would be the way I would hook it up for a customer. Much cheaper than flexible cord.
Agree. That's why I asked if the OP wanted a plug and a flexible connection that can be physically disconnected.
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That being said, if it had made it this long on solid wire there is no need to mess with it.
Agree, assuming the terminals are suitable.
