Wiring my plasma cutter

[thinkracing]

I bought a Plasma cutter that needs to be wired for a 110/220v three pronged plug. The wiring diagram I received references different colors.

My unit has a Black, White and Green wire. Without providing any more information, are there general rules by color that denote the role of each wire. Is black still ground?

Thanks.

 

[q miester]

since this is ac voltage the following is typical coloring code
120v Black is 120 hot white is neutral and green is ground (always green is ground)
240 v with your colors Black(L1) is 120v hot, White(L2) is 120v hot and green is ground
240 typical colors black(L1) is 120v hot, red (L2) is 120v hot, white is neutral and green is ground.
12v dc is red hot 12v, black is negative(ground)
and i wont start 480 v or 2300 etc no need to here

 

[W_A_Watson_II]

Does your plug look like this?

NEMA 10-50P​

If so the black and white are separate 110/120 volt legs (L1 & L2) and the GREEN is ground.

 

[AussieDan]

The plug pictured above looks like a NEMA 10-50 which is a non-grounded 125/250 volt with 2 hot legs and a neutral (no ground).

My understanding is that you would have either a 250-only NEMA 6-50 (hot/hot/gnd - common for welders), or if the plasma cutter is actually 125/250 then you'd need a 4-pole NEMA 14-50 (hot/hot/neutral/gnd - common for dryers).

Check the specs on the plasma cutter, you most likely want the 6-50.

6-50 250-volt grounded

14-50 125/250-volt grounded

 

[Norcal]

Does your plug look like this?

NEMA 10-50P​

If so the black and white are separate 110/120 volt legs (L1 & L2) and the GREEN is ground.

That attachment plug is NOT a grounding plug, it has 2- ungrounded (hot) and 1- grounded (neutral) conductors. A 3-wire 50A range plug was never a grounding type, and this also applies to a 30A 3-wire dryer plug too, if you read the rating it will say "50A 125/250V" (or 30A), which makes it a dual voltage device.

Prior to the 1996 NEC it was allowed to ground the frame of 120/240V cooking & laundry appliances to the neutral, after that it was prohibited in all new installations.

 

[AussieDan]

Exactly, so to properly wire a 50A 125/250V appliance you should use the 14-50 4-prong plug that has hot/hot/neutral/gnd.

If the plasma cutter only has 3 wires (black/white/green) it is most likely straight 250V (and should use the 6-50), but you'll need to check the manual and/or specification plate to find out.

 

[Norcal]

Exactly, so to properly wire a 50A 125/250V appliance you should use the 14-50 4-prong plug that has hot/hot/neutral/gnd.

If the plasma cutter only has 3 wires (black/white/green) it is most likely straight 250V (and should use the 6-50), but you'll need to check the manual and/or specification plate to find out.

If the plasma cutter has 4-wires it's 3 phase....

 

[AussieDan]

Yeah, I don't know too much about plasma cutters, it looks like the "110/220V" models don't actually use both 125 & 250V simultaneously like a dryer, you use 3-wires and hook it up to either 125 or 250V.

So, you'd want the 6-50 for a 250V hookup (black-hot/white-hot/green-gnd) or for 125V (black-hot/white-neutral/green-gnd) it'll run off a standard outlet.

An example from the Hobart AirForce 500i spec sheet: "10 ft. (3 m) power cord with 5-15P (115 V, 15 A) and 6-50P (230 V, 50 A) MVP plugs"

 

[Skyline]

@thinkracing:
One thing for sure...if you have access to the 220v where you want to plug in the plasma cutter, that is what you should use. The performance of the machine is likely to be better with the higher voltage.

 

[sberry]

Yeah, I don't know too much about plasma cutters, it looks like the "110/220V" models don't actually use both 125 & 250V simultaneously like a dryer, you use 3-wires and hook it up to either 125 or 250V.

So, you'd want the 6-50 for a 250V hookup (black-hot/white-hot/green-gnd) or for 125V (black-hot/white-neutral/green-gnd) it'll run off a standard outlet.

An example from the Hobart AirForce 500i spec sheet: "10 ft. (3 m) power cord with 5-15P (115 V, 15 A) and 6-50P (230 V, 50 A) MVP plugs"

You got it, this is correct.