Wiring issues from panel to 6.5hp compressor

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  #1  
Old 09-20-15, 06:52 PM
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Wiring issues from panel to 6.5hp compressor

I am in the process of finishing my 30X40 pole building which includes a 6.5 hp compressor. I put a 40 amp double pull breaker in the panel and ran 10 gauge wire roughly 50 feet to the compressor. I got the wire free from work but it wasn't sheathed so I ran two blacks and a green wire through flexible conduit. I have power at the panel on both black wires but when I test at the compressor only one has power. Is it possible to have that gauge of wire be bad? It's a straight run with no junctions.

Thanks for any and help
 
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Old 09-20-15, 06:55 PM
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Welcome to the forums.

Piece of wire bad..... not very likely.
#10 copper wire should be protected at 30A.

Check for 240 VAC at the breaker and then again at the compressor.
 
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Old 09-20-15, 09:00 PM
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thanks PJmax....what's the best way to check the 240 VAC??


thanks
 
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Old 09-20-15, 09:30 PM
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what's the best way to check the 240 VAC?
Measure between the two blacks where they connect to the compressor if hard wired. Test at the receptacle between the two hot slots if you have a cord and plug.
but when I test at the compressor only one has power.
Use the ohm scale to test your two black wires for continuity. Disconnect the wires at both ends, connect the wires together on one end, and and test between the other two ends for continuity.
 

Last edited by ray2047; 09-21-15 at 12:25 PM.
  #5  
Old 09-21-15, 10:20 AM
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6.5 HP is not a standard single phase motor size, are you sure it isn't either a 5 HP or a 7 1/2 HP? Based upon the Square D Motor Data Calculator, a 5 HP motor would use #10 wire and a 60A breaker. If you have a 6.5 HP motor, I suspect it might need #8 wire to it. Where did you get the info for wire size and circuit breaker for the compressor?

Single Phase Motor Data
 
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Old 09-21-15, 11:52 AM
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Does the barn have adequate service for that size motor? Pretty good sized for what you normally find in a residential outbuilding.
 
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