Welding Tips and Tricks

Hey folks,

I'm in the process of planning to add 240V to my shop.

I currently have a Maxstar 150 STL and in the manual it says the recommended breaker for a 240V circuit is a 20 amp 2 pole breaker. Sure, that's easy enough. A Maxstar 200 recommends a 30 or 40 amp breaker depending on input voltage, which one day I may upgrade to (or dynasty, or pick your brand of choice..).

In the Maxstar 150 manual:

Receptacle − NEMA Type 6−50R(Customer Supplied)
Follow electrical service guide for 230 VAC in Section 4-8. Do not use plug rating to size branch circuit protection.

That being stated, I image they use a NEMA Type 6-50R so that all their machines with MVP can use the same MVP plugs. However, is this allowed per NEC code? Can I use a 20 amp breaker with a 50A receptacle legally for a dedicated circuit?

If I upgrade to something like a dynasty as an example, I would then have the same problem, as I'd have to wire the machine with the same plug, which would mean the receptacle is stating a false circuit amperage.

Hope that makes sense. Thanks!

When they list a breaker size in a welder manual, they are talking about the minimum acceptable circuit.
The breaker in the panel is sized to protect the wiring between the panel and the plug. If you use #6 wire from the panel to the NEMA 6-50 plug, then you can use a 50 amp breaker.
If you instead use #12 wire, the the largest acceptable panel breaker would be 20 amps.
If the plugged in device only needs 20 amps, it will work fine on either circuit. If it needs 45 amps, it will need the circuit that has the #6 wire, and the 50 amp breaker.

Thanks for the explanation. That makes sense, after a bit more reading on the subject you are right on point.