Box fill caclulations with #4 wire

[600SL]

Hello I setting up my welder and I would like to use the largest wire possible for my Nema 6-50R receptacle. The receptacle will fit up to #4 wire and #2 for ground. But box size calculations for in Table 314.16(B) only address down to #6 AGW. I plan on upgrading my welder so I would like to put in the biggest wire possible. If I assume a #4 is 7 Cu then my setup with 6 largest conductors for a double sized devise + 2 #4 conductors = 6x7=42 + 5 cu for a number 6 ground = 47 Cu.. Since 52 Cu is about the largest standard box and cover combination I can find, I will be over the limit if a #4 counts as 8cu.

 

[Mustang51js]

Once you go up in sizes it goes by the diameter of pipe you would be installing, if I remember it's x8. You would prob have to go with a deep 9 11/16th box. But honestly your just wasting money going with bigger wire if it's only 50 amps. Your not gaining anything unless your run is a 100 feet long for voltage drop.

 

[600SL]

Once you go up in sizes it goes by the diameter of pipe you would be installing, if I remember it's x8. You would prob have to go with a deep 9 11/16th box. But honestly your just wasting money going with bigger wire if it's only 50 amps. Your not gaining anything unless your run is a 100 feet long for voltage drop.

I'm not trying to gain anything for the moment. I would just like to upgrade my welder in the future and would hate to have to pull the wire again. The NEC has very specific rules when it comes to welders. This machine, Lincoln Square wave 175 pulls 65 amps when welding Aluminum at max current but the recommended installation is a 50 amp receptacle with #8 wire and a 125 amp breaker. Going to number 4 wire boost the capability by 70%. That means I should be able to upgrade my welder to ~ 300amps possibly 350 with a new technology inverter welder.

 

[Mustang51js]

I think the issue is when you go that big they are supposed to be hard wired. The problem is your limited by a box that you can mount the outlet to. If you had to you could do a 1900 box with an extension on that to get the bend into the outlet

 

[600SL]

I just went and purchased #6 wire. I figured if and when I upsized my welder it will probably require #2 anyway and the #4 would have been a waist. I got a 6" x 6" x 2.5" box with a cover that holds the 6-50R.

Problem solved for the moment.

Thanks everyone.