Electrical connection requirements

[Broccoli1]

I don't believe I do. To a three phase load there is no wild leg. To single phase loads center tapped Delta can supply 240 using any combination of A,B,or C. Using the center tap you can get 120 volt or 208 volt. A machine not connected to neutral won't see a wild leg. I don't like the term wild leg. There's nothing wild about it. It is simply 1.5 phase coils from neutral.

I'm pickin up what yer layin down now

[WillieB]

All electrical circuits are round trip to flow current steadily. To test voltage, or potential, the voltmeter has two leads. Connect one lead to any live point, nothing happens. Therefore, it is fair to say voltage or potential is the difference between two conductors. To read 120 or 208 one lead must be on neutral or center tap.

[WillieB]

You contradict yourself with the first sentence and last sentence.

Phase b is the "wild" leg or High leg

http://www.bmillerengineering.com/elecsys.htm

I don't believe I do. To a three phase load there is no wild leg. To single phase loads center tapped Delta can supply 240 using any combination of A,B,or C. Using the center tap you can get 120 volt or 208 volt. A machine not connected to neutral won't see a wild leg. I don't like the term wild leg. There's nothing wild about it. It is simply 1.5 phase coils from neutral.

[Broccoli1]

Again, in three phase Delta applications there is no wild leg. Thinking of the triangular shape of a delta connection, a volt meter measuring any combination of two of the corners will measure 240 or close to it, each transformer coil provides 240. Such a transformer can supply 240 single phase across any two terminals. We also want to supply 120 volt loads, for this reason we center tap one of the three secondary coils. From this center tap or neutral we can supply 120 volt loads to either end of said coil. Or, from the center tap to the opposite terminal supplies voltage from 1-1/2 of the coils. This provides 208 volt single phase.

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You contradict yourself with the first sentence and last sentence.

Phase b is the "wild" leg or High leg

http://www.bmillerengineering.com/elecsys.htm

[WillieB]

Again, in three phase Delta applications there is no wild leg. Thinking of the triangular shape of a delta connection, a volt meter measuring any combination of two of the corners will measure 240 or close to it, each transformer coil provides 240. Such a transformer can supply 240 single phase across any two terminals. We also want to supply 120 volt loads, for this reason we center tap one of the three secondary coils. From this center tap or neutral we can supply 120 volt loads to either end of said coil. Or, from the center tap to the opposite terminal supplies voltage from 1-1/2 of the coils. This provides 208 volt single phase.

Harbor freight type 120 volt welders use a neutral. I'm not aware of 208, 240 single phase, or any voltage three phase machines being connected to neutral.
For this reason the welder isn't exposed to a wild leg.

As has been pointed out many electricians are guilty of load imbalance. Three phase loads are pretty well balanced. Often, all the single phase loads are put on one phase. The odd leg gets less load. uneven loading can cause imbalanced voltage. This can cause problems in motors, and perhaps welders. 5% imbalance in phase voltage can cause big heat build up in motors.

[FusionKing]

I use a lot of adapters on my stuff when needed. My machines are wired with the wild leg on the red wire. The single phased adapters use the black and white wires.
I only makes sense to me that a wild leg should be hooked to the only extra wire that is only used for three phase.
That said.....tester shows it doesn't matter. I still prefer to play it safe.

[Bodybagger]

In the case of that Power Wave I got, I suspected correctly that the wild leg was being overutilized from a not-so-beefey transformer and it sensed the voltage out of tolerance and shut down. Yes, the welder had no clue about any other loads in the service and there was no neural hooked to it. But what it DID see is that the phase-to-phase voltage between the L1 and L3 terminals dropped out of tolerance (which wouldn't have mattered if they hadn't hooked the wild leg onto the the L3 terminal as that particular welder sensed voltage between L1 and L3). The problem was due to random single phase loads between the neutral and wild leg and had nothing to do with the service or the welder. This is something that should be taken into account. The wild leg is not a crutch to run everything on and can cause problems particularly if you have single phase motors running (starting) on it. You can't assume the rest of the electrical layout of any place is done using best practices and problems elsewhere can show up with perfectly good equipment connected to the same service. Hence, find out what terminals the control board senses input voltage from and make sure the wild leg is NOT connected to one of those terminals, or if that's not an option, make sure other loads on the service do not cause an out-of-tolerance supply and you'll avoid having things happen like the welder shutting down randomly when a motor kicks on in another part of the building.

[unionsparky]

As I said in the beginning, I'm not a welder. I am not completely familiar with all the in's and out's of Miller's equipment. As you pointed out (in question) the Miller 350 does not operate on 120V.

There is still 208V to ground regardless of neutral connection. It is simply a matter of how the innerworkings of the welder are setup. It appears my concerns were over nothing.

It is hooked up 3 phase and working. My problem is solved. Thanks!

[WillieB]

Does the 350 have auto line? The Dynasty 280 has "auto line" Miller's system that adjusts itself to supply voltage at any point in a range. I want to say the Dynasty works on anything from 198 to 500 volts Three phase uses red white, and black. Single phase uses white and black, tape up red from welder cord. Single phase 208 would work, but I can't think why I would want to use it.

[WillieB]

A Miller Matic 350 connects to 120Volt?

[WillieB]

Does the welder connect to neutral? If it does it is the first I've seen connected to neutral. Without neutral there is no high leg. Delta is three transformer windings connected in a triangle diagram. The wild leg or 208 is neutral to the opposite corner of said triangle. Your welder doesn't know about 208.

[unionsparky]

Delta 120/208/240 Three phase is 240 balanced on three phase. 240 single phase is available from any phase 120 single phase is available from 2 legs to neutral. 208 single phase is available from the high leg to neutral.

I'm completely aware of how their service functions. My lack of familiarity is with Miller welders. My question was, if the 208V high leg could damage any control circuits that were expecting to see 120V.

If it works on three phase, why not use three phase?

It is connected to 3 phase. I only brought up the 240V single phase scenario as a matter of trying to determine if the equipment would be unhappy with the 208V on a certain leg of the supply. Since the unit is capable of 120V operation, is it entirely possible that the single hot configuration may want only 120V. This would mean that the second conductor used, when connected as single phase 240V would most certainly have to accept 208V on that leg, since I'm sure Miller would not sell equipment that wouldn't have the option to connect single phase 240V to a high leg delta, which could be necessary if the customer has space constraints.

It is hooked up and working at 230V 3 phase connection settings.

Thanks again everyone!

[WillieB]

If it works on three phase, why not use three phase?

[WillieB]

Delta 120/208/240 Three phase is 240 balanced on three phase. 240 single phase is available from any phase 120 single phase is available from 2 legs to neutral. 208 single phase is available from the high leg to neutral.

[unionsparky]

Well, I decided to put high leg on B phase, white in cord. I saw elsewhere that red is unused for single phase. Meaning that if it has any sensitivity to high leg on A, white must be acceptable. I can't see Miller making equipment that can't be connected to center tapped deltas via single phase.

Thanks for all the replies.