Hook up for welding machine

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Bkratky

Member
Location
Houston tx usa
I have a thermal arc 186 welder that requires 208 or 230 v. It says single phase also. It requires a 6-50P nema receptacle. I have a 120/240 delta panel 3 phase, with a 208v high leg. Can I run a 208 high leg circuit with a neutral and ground(3 wires) or does it have to be 240volt 2 hots and a ground? Also 240v fed from a 2 pole breaker in a 3 phase panel would be fine for single phase welder right ?
 

iwire

Moderator
Staff member
Location
Massachusetts
I have a thermal arc 186 welder that requires 208 or 230 v. It says single phase also. It requires a 6-50P nema receptacle. I

For what it is worth a 6-50P is a male plug for a cord. Ask the supply house for a 6-50R if you need a receptacle.

have a 120/240 delta panel 3 phase, with a 208v high leg. Can I run a 208 high leg circuit with a neutral and ground(3 wires) or does it have to be 240volt 2 hots and a ground?

I don't work with high leg systems so I can't help you there.

Also 240v fed from a 2 pole breaker in a 3 phase panel would be fine for single phase welder right ?

Yes.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
...... Can I run a 208 high leg circuit with a neutral and ground(3 wires) or does it have to be 240volt 2 hots and a ground?
If you need a neutral then you need to be sure that you don't use the high leg. That should mean landing your breaker on A and C phase, but you need check, some old or miswired systems will not have the high leg on B phase.

Also 240v fed from a 2 pole breaker in a 3 phase panel would be fine for single phase welder right ?
Yes. If you don't need a neutral you can grab any spaces where a two pole breaker will fit.
 

FREEBALL

Senior Member
Location
york pa usa
My experience with high leg is back in the day they landed the high leg on 4 wire center tapped delta systems on the C phase so there was flexibility in regards to120/240 volt single ph. loads, like subfeeds. Now when it comes to the 2 pole breakers the breaker has to be rated for lets say 240 volt per phase. example a 2 pole qo breaker is not adequate because its only rated 120v per phase. you need perhaps a straight 240v breaker or 277v 2 pole breaker. and no you need two phases for the 230 volt to operate correctly. This is what information I obtained when dealing with a project a year or so ago. Its funny though all the panels that were added in the facility had QO 120/240 ratings. I believe the NEC reference is 240.85
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
141218-2341 EDT

If you have a 240 V delta with a wild leg this means to me that most probably you have one large 240 V center tapped single phase ultility transformer, and one or two smaller transformers connected to the wild leg. The large single phase transformer is used to supply the 120 V circuits.

For the welder you most likely want to operate from 240 if it is available, and in this case the transformer used to supply the 120 V single phase circuits. This provides neutral if required. Probably causes more light flickering because the source is common to the likely lighting circuits. You can use the standard QO 2 pole breaker when supplied from the 240 center tapped transformer.

.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
141218-2341 EDT...... You can use the standard QO 2 pole breaker when supplied from the 240 center tapped transformer.
Point of order if the Chairman will permit.

If your 240V circuit includes the high leg of a delta system then the circuit breaker must be straight 240V rated to be NEC compliant. Most two pole breakers are slash rated 240/120V, meaning they are only to be used when the voltage is 120V to ground.
 

Bkratky

Member
Location
Houston tx usa
If you need a neutral then you need to be sure that you don't use the high leg. That should mean landing your breaker on A and C phase, but you need check, some old or miswired systems will not have the high leg on B phase.

Yes. If you don't need a neutral you can grab any spaces where a two pole breaker will fit.



The high leg in this panel is C phase. So I was wondering if i can still run 1 wild leg with a neutral and a ground instead of 240v 2 wire hot and ground.
 

kwired

Electron manager
Location
NE Nebraska
If you use the wild leg your breaker needs rated at least 208 volts. If you use a two pole breaker, there are straight 240 volt breakers available as some have already mentioned. If you use a single pole breaker - you are not likely to find one rated more then 120 volts unless you are using a panel/breaker system rated for 277/480 or more.

How much power you can draw from that wild leg will depend on the system supplying it. If if is open delta with limited sized transformer for the high leg - you need to watch what you add more closely then if it were a full delta with three equal sized transformer coils, and this applies whether connecting high leg to neutral or high leg to another phase.

If the machine comes with a 6-50 plug, it shouldn't require a neutral for the purpose of supplying 120 volt loads, if it needs a neutral for that purpose they should have installed something like a 10-50 plug.
 

Bkratky

Member
Location
Houston tx usa
Also I noticed that the plug is rated for 50 amps, so i was thinking of looking for 50amp breakers, but ive read elsewhere that people with the same machine used 30amp breakers, doesnt by code you have to protect the outlet with the same rating as the receptacle?
 

kwired

Electron manager
Location
NE Nebraska
Also I noticed that the plug is rated for 50 amps, so i was thinking of looking for 50amp breakers, but ive read elsewhere that people with the same machine used 30amp breakers, doesnt by code you have to protect the outlet with the same rating as the receptacle?

Code or not, with the 30 amp breaker you will not get machine's full rating out of it without tripping the breaker.

That said I have a welder(with 6-50 cord cap, not sure about any other ratings off top of my head) that I have taken out and used running from a 8000 watt portable generator, which only has a 30 amp receptacle and breaker. As long as you don't crank the weld setting too high or cycle for too long you can get by in such situations, but may occasionally need to reset the breaker.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
141219-0910 EST

ActionDave:

I thought my statement was relative clear. But I will restate it differently. If you use the 240 legs from the center tapped transformer of a wild leg delta system, then the voltage of either leg to ground is 120, and therefore, a standard two pole QO breaker can be used.


Bkratky:

Why do you want to use 208 from a wild leg system? Using 240 is a better choice. Most wild leg deltas have a large single phase transformer for 120-0-120 because of a large single phase load, and in turn the single phase source has a lower internal impedance. A load from the wild leg to neutral is a poor way to load one of these systems.

.
 

Bkratky

Member
Location
Houston tx usa
If you use the wild leg your breaker needs rated at least 208 volts. If you use a two pole breaker, there are straight 240 volt breakers available as some have already mentioned. If you use a single pole breaker - you are not likely to find one rated more then 120 volts unless you are using a panel/breaker system rated for 277/480 or more.

How much power you can draw from that wild leg will depend on the system supplying it. If if is open delta with limited sized transformer for the high leg - you need to watch what you add more closely then if it were a full delta with three equal sized transformer coils, and this applies whether connecting high leg to neutral or high leg to another phase.

If the machine comes with a 6-50 plug, it shouldn't require a neutral for the purpose of supplying 120 volt loads, if it needs a neutral for that purpose they should have installed something like a 10-50 plug.

Got you, wild leg idea for me is dead. I need to either tap from a 120/208 panel with 2legs, or 120/240v (Cphase high leg) and get 2 hots from a 2 pole on A and B phases.
 

Bkratky

Member
Location
Houston tx usa
141219-0910 EST

ActionDave:

I thought my statement was relative clear. But I will restate it differently. If you use the 240 legs from the center tapped transformer of a wild leg delta system, then the voltage of either leg to ground is 120, and therefore, a standard two pole QO breaker can be used.


Bkratky:

Why do you want to use 208 from a wild leg system? Using 240 is a better choice. Most wild leg deltas have a large single phase transformer for 120-0-120 because of a large single phase load, and in turn the single phase source has a lower internal impedance. A load from the wild leg to neutral is a poor way to load one of these systems.

.


I was just looking into use a wild leg cuz i have very little space in my Panel for 2 pole breakers, and i need to add 2 outlets for the welders. But I might have enough space Barely to put 2 double pole breakers in there just have to rearrange.
 

kwired

Electron manager
Location
NE Nebraska
141219-0910 EST

ActionDave:

I thought my statement was relative clear. But I will restate it differently. If you use the 240 legs from the center tapped transformer of a wild leg delta system, then the voltage of either leg to ground is 120, and therefore, a standard two pole QO breaker can be used.


Bkratky:

Why do you want to use 208 from a wild leg system? Using 240 is a better choice. Most wild leg deltas have a large single phase transformer for 120-0-120 because of a large single phase load, and in turn the single phase source has a lower internal impedance. A load from the wild leg to neutral is a poor way to load one of these systems.

.
I can show you many full delta's that have three equally sized transformers with one of them grounded at the center tap - they were used because the load is primarily motor loads and why use 208 when you get a little more bang for your buck with 240. In fact out in the rural areas here 208/120Y is somewhat rare, unless you come up with a facility that has a significant amount of 120 volt load.
 
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