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240v receptacles - what to use?

828 views 6 replies 6 participants last post by  PAToyota 
#1 ·
OK Here's the dilemma.

Around the shop I will have 5 240v (single phase) outlets. For the welder. plasma, etc...

The welder & plasma both have 3 prong "dryer" plugs (like a large version of the standard 110v 15a plug). I believe it's called a NEMA #6-50.

I heard that "the code" no longer allows 3 prong plugs and that it must be 4 prong now (2 hots, neutral & ground).

First question, what 4 prong plug is the most common? Is it twist-lock?

Second questions, how do I wire up my plasma/welder to a four prong plug, if it's only got 3 wires? do I leave the ground off?

thanks in advance,

REFLEXX :D
 
#2 · (Edited)
Reflexx said:
I heard that "the code" no longer allows 3 prong plugs and that it must be 4 prong now (2 hots, neutral & ground).
Say what? Can anyone confirm? Is this a municipality, state, or national thing?

I hope this isn't true, all my stuff is three prong, and I personally like the simplicity of two hots and a ground. It's easy to pull, easy to wire and hard to screw up.


Reflexx said:
Second questions, how do I wire up my plasma/welder to a four prong plug, if it's only got 3 wires? do I leave the ground off?
If this is true I'd look for a way to build an adapter that'll accept the 3 prong on all your equipment, then plug into the wall 4-prong. One or two adapters can be moved between equipment as necessary.
 
#3 ·
D60 said:
Say what? Can anyone confirm? Is this a municipality, state, or national thing?
Ultimately, it's going to be up to the local municipality. State codes may say one thing, but local gubmints can always be more strict. If you only needed 3-prong when you built the old shop, I doubt anything has changed since then. Don't you have a brother-in-law or something that's licensed in CO? Ask. :flipoff2:

The four-prong deal frequently depends on application, too.
 
#4 ·
4 prong is required for new appliance installations. Dryers, etc. At least in most municipalities. It's not a requirement for 220v tools (welders, table saws, jointers etc etc etc)
 
#6 · (Edited)
I believe the goal is to eliminate ungrounded receptacles. The 10-30R and 10-50R (old stove and dryer) are 3-prong and fall into this category.

As long as the 3-prong configuration you are using has a ground prong it should be legal.

The 6-50R is more of a "welder" plug AFAIK. The modern dryer plug is a 14-30R and is a 4-prong type.
 
#7 ·
You are mixing up requirements. Four prong plugs are required for anything that is 110/220V so that you have both hots (for the 220V and one of the hots for 110V), the neutral (for the 110V), and the ground (for both 220V and 110V). These are only for something like a dryer or range which uses 220V for the heating elements and 110V for the lights and such.

A welder, compressor, or such is JUST 220V - there is absolutely no need for a neutral. You have the two hots and a ground. One more time - NO NEUTRAL.

So, no change to the code as far as for what you are doing.
 
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