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Upgrading cable in a NEMA 6-50R outlet


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The following quotes were originally part of my thread on Converting an inverted hydraulic press into a light duty forging press, now split out into a separate thread regarding the question that follows.

On 5/2/2020 at 11:38 AM, JHCC said:
On 5/2/2020 at 10:46 AM, Steve Sells said:
On 5/2/2020 at 10:44 AM, JHCC said:
On 4/24/2020 at 12:24 PM, Steve Sells said:

you would need 6 GA al wire to  safely handle 50 amps. 8ga for copper. ( 10 ga copper is safe for 30 amps, the voltage drop and flex cables wear and tear over time is why I said to use 8ga for the 5 HP motors SO cord @ 120v)

Steve, my local electrician friend tells me “#8 copper is rated for 40A. Of course code is always a wee bit conservative but I wouldn't advise pulling 50A on #8 wire.” 

I’m going to go ahead and wire the socket with 8 ga for now, as I am only going to be running the 5hp motor on The Pressciousss at present. If I ever do get a 220 volt welder, I can always run some 6 ga wire from the socket to the junction box. Does that sound right?

I am typo king but my numbers are correct for thhw/thwn, he could he thinking UF which is only rated for 40, as I said before installations effect amperage, that includes insulation type as well as length

I double checked the rating of the wire that I bought, and its maximum amperage is 40 (I really should have checked before placing the order. Oh well; live and learn. 

Well, the day has come, and I need to run some new wire to accommodate my new stick welder. However, I'm a bit confused: the manual for the welder (a Lincoln (not "A. Lincoln") AC-225-S tombstone says "#10 or larger copper wires are required if conduit is used. For long cable runs over 100' (31M), #8 or larger wire in the conduit will be needed to prevent excessive voltage drops." The cable that's in place right now (the stuff I bought originally with the 40 amp rating) is 8/2 NM-B Romex, which is not run through conduit. Am I correct that I still need to upgrade the cable to 50 amps?

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Its funny how you guys use so much less amp over wire. 6GA is 16mm2 over here, and we pull 10 amps per mm2.

As Steve says, bigger is better. But what also plays a role is how the cables are mounted. Are the close to other things, poured in concrete, I a pipe. etc etc

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