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Steve G.
Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 17987
Experience:  Spent 20 years as an Electrical Engineer, designing electrical plans and specifications.
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I installed a electrical vehicle charging station in my garage.

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I installed a electrical vehicle charging station in my garage. It is L2, providing 6kW of power or 25A @240V. I used 50Ft of 10/3 alum flexible conduit with a 30A breakers. When in use, the conduit is very warm to the touch. 10 AWG is 1 ohm per ft, yielding 30W per line over 50ft. Is this connection underrated for the load? What should I have done. Thanks

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Are your conductors copper or aluminum?

Please let me know so that we can continue.



Customer: replied 4 years ago.

solid copper

Ok, your #10 conductors in MC are good for 30A. 50 feet is not a long run either.

Do you actually have 240V at the equipment? Or maybe 230 or 220?

Can you check that?

Customer: replied 4 years ago.

Yes, I measured 240VAC RMS between phases with Fluke digital meter at the receptacle with no load. With load, I see about 237VAC


Ok, for continuous loads, the NEC requires that you breaker (and wiring) be rated 125% of the full load of the equipment. 25A x 1.25 is 31.25A.

Your breaker and wiring should be rated for 40A - the next common size up from 31.25

That would be to comply with code, however, when it boils down to it, #10 conductors are good for 25A so I'm not sure why they are warm for such a short run.

Are you sure that the load is 6KW?

Please let me know so that we can continue.



Customer: replied 4 years ago.

OK. I had 40A breaker originally but reduced it thinking 40A was too high.


I have a residential-type power meter in series with this load so I can watch power draw when charger is in use. From that I confirm 6kW, consistent with charger and car specs.


I calculate about 1W/ft power dissipation in the conduit from 0.9989 ohm/1000ft from table online. Don't know if that is enough to create a warm temp.



A colleague reminded me that that the 125% requirement is not a suggestion :) It is there for this very situation - a continuous load is going to warm up those conductors.

You really should be using a 40A breaker and #8 conductors.

Please let me know if I can help you further.

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