Conduit Sizing

[Bruce Ramsey]

Buddy just got a new Tesla all electric car. You can charge the car at home with a 50 amp circuit. He has a 50 amp receptacle he currently uses for his table saw. He wants to run a new set of wires from the 50 amp breaker in the panel across the ceiling of the garage via conduit and mount a receptacle convienent to charge the vehicle.

He is planning on using a 6-3 with a 10 ground. He wants to use the proper size conduit. Can someone help point me in the correct direction in the NEC to help size the conduit?

[Jim Port]

The tables in Chapter 9 will be used to size the conduit.

Note that the major diameter of the cable needs to be used in the calculation if elliptical.

[Garry Sorrells]

Dang, table saw with a 50amp breaker. Must be a Tim The Tool Man saw. 50HP motor?

[Brad Richter]

A single NM cable in a pipe is considered a single conductor. As result conduit fill is allowed @ 53%. Southwire 6-3 w/g is listed with a diameter of 650 mils(.65") which is .332 square inches. I believe a 1" pipe would be compliant. Hope it's a straight pull. :confused:

[Donald Farrell]

Can you please show me in the NEC where you size conduit by the OD of an NMB cable?

[Jim Port]

Don, this is Note 9 from the Notes for Chapter 9.

(9) A multiconductor cable or flexible cord of two or more
conductors shall be treated as a single conductor for
calculating percentage conduit fill area. For cables that
have elliptical cross sections, the cross-sectional area
calculation shall be based on using the major diameter
of the ellipse as a circle diameter.

[Rollie Meyers]

Dang, table saw with a 50amp breaker. Must be a Tim The Tool Man saw. 50HP motor?


Motor rules are different & W/ a 5* HP motor & meeting the conditions specs in art 430 means that 50A is prob. fine.

* OP did not spec HP, so just a guess on my part.

[Bill Kriegh]

Is the entire length of the cable going to be in conduit or just a short section? (like for protection down a wall)

If the cable is using the conduit for protection for only part of its' length the fill tables don't apply - - Notes To Tables for Chapter 9 (2)

[Donald Farrell]

Hi,

I was just re-reading the OP and I noticed that the "Buddy", says he has a 50 Amp Recep., not a 50 Amp circuit. I've played with some woodworking equipment in my time, but a 50 amp tool would be awesome! Not to mention the rest of the tools in that playroom!

I guess I'm curious as to the relevance of the receptacle at all since as indicated in the OP, it needs to be moved and a new cable installed
why not do a whole new circuit an be done with it. Unless he is panning on tapping off of the 50 amp recep which means that now the amperage o the existing circuit needs to be verified to make sure it is sufficient to charge the vehicle.

[jack davenport]

Hi,


I guess I'm curious as to the relevance of the receptacle at all since as indicated in the OP, it needs to be moved and a new cable installed
why not do a whole new circuit an be done with it. Unless he is panning on tapping off of the 50 amp recep which means that now the amperage o the existing circuit needs to be verified to make sure it is sufficient to charge the vehicle.

The OP stated the "buddy" was going to run a new set of wires from the 50 ampere breaker in the garage panel. The 6-3 in a 1" emt will work. Personally I would just use 3 #6 thhn and a #10 thhn instead of fooling around with trying to pull a nm cable in the conduit. As a side note: stripping the jacket off the NM and using the conductors by them selves is a code violation as the individual conductors in NM do not have the code required markings on them.

[Rollie Meyers]

If conduit was being used 8 AWG THHN is good for 50A.