Question for John T

Miller welder has two receptacles on face It gets fed with two hot legs and a ground . So these receptacles are derived on the secondary side somewhere and protected as such? Protected by
electronics on the secondary and no current is traveling on ground back to the panel ? I guess Miller knows what they are doing but it seems a bit weird .

Not too wierd. a floating ac circuit with no ground can be safer around things that are grounded. Thus a trouble light, or angle grinder will have no circuit path to electrocute an operator. Jim

dr, Ive had occasion to study Grounding and Bonding for on site construction type of gensets (but wayyyyyy back when I practiced power distribution, maybe things changed??) and Im "guessing" the secondary output of a welder/generator might fall under the same rule BUT NO WARRANTY.

Heres my understanding: OSHA (if that matters or applies ??) calls for portable gensets used on construction sites TO BE BONDED (Neutral Ground are Bonded) BUT NOTTTTTTTTTTTTTTT GROUNDED. They want the NG bond so if theres a hot short to case/frame etc the safety equipment GroundiNG Conductor provides a return path for fault current so the breaker trips IF THERE WERE NO NG BOND THE GROUND WIRE IS USELESS IE They want a NG Bond

HOWEVER due to possible wet conditions they DO NOT want the genset bonded to a Grounding Electrode such as a rod into mother earth

As you know Neutral carries normal return current while the Ground is ONLY for fault current return. I assume the welders secondary is an ISOLATION TRANSFORMER NOTTTTTTTTTTT AN AUTO TRANSFORMER. It becomes a Separate Derived Source necessitating ITS own protection.

There is one other exception (besides OSHA above) to the requirement a genset configured as a Separate Derived Source DOES NOT NEED GROUNDED and thats where it serves plug and cord connected tools via onboard receptacles

I would Bond it but NOT Ground it

John T Longggggggg retired n rusty power distribution engineer so noooooooooooo warranty

You still across the pasture from me. Be safe on your trip.

The wiring diagram for your welder would be the definitive answer, but my guess is the AC outlets are floating from ground, while their grounds are tied to the welder's chassis ground and the power cord ground. As JAN said, this is a fairly common and safe arrangement; most medical and laboratory devices employ some sort of isolation transformer to prevent electrical shock.

Yo drsporster, here's a bit more info for you.

I was at an NEC Seminar once where there was a demonstration where a piece of equipment plugged to the wall outlet then a transformer was near a tank of water and there were wires leading into the tank etc. all sorts of scary looking stuff leading one to believe you would be electrocuted BUT THE VENDOR DIPS HIS HAND INTO THE TANK............

The thing is the equipment is FIRST plugged into an ISOLATION Transformer which its Secondary IS NOT GROUNDED that is unlike the typical 120/240 Volt Single Phase Three Wire service and distribution which IS GROUNDED.

Typically a portable genset's output (likely the welder) is similar to how an Isolation Transformer is configured. There is no direct electrical connection between the input energy source and the output. THERFORE typically the gensets output or a transformers output MAY OR MAY NOT NOT BE GROUNDED OR MAY OR MAY NOT BE BONDED (see below).

Per the NEC when I last practiced power distribution design a Genset (or could be your welder) iffffffffffffff it was configured as a Separately Derived Source REQUIRED CONNECTION TO A GROUNDING ELECTRODE including but NOT limited to a "Made Electrode" such as a rod driven into earth

HOWEVER Grounding is NOT required 1) If the genset (or perhaps your welder) serves plug and cord connected tools using onboard receptacles orrrrrrrrrrrrr 2) Its a construction generator where OSHA required BONDING but NOT Grounding

Soooooooooo what you describe is typical I dont see any problem if alls well (its likely the same as an isolation transformer or genset). If its configured as a Separate Derived Source sure GROUND IT............If its used like a construction site genset BOND it but DO NOT GROUND IT.

NOTE for good reason some gensets come from the factory with a BONDED Neutral others a FLOAITNG Neutral and that depends on how they are used, if you need that explained let me know. For the most part most (not all) non electricians most (not all) non power power engineers DO NOT understand Grounding or Bonding and the difference, so don't feel bad or alone lol.

DISCLAIMER Noooooooo warranty its been years since I was a power distribution design engineer attending NEC seminars regularly and codes change this is my best recollection of how it was when I practiced

John T

Thanks Billy, take care

John T

Bonding can save your life grounding not so much.

I think he is talking about the 11t5v plug on a welder not a genset. Lincoln does the same thing,great for a grinder.

(quoted from post at 17:39:29 01/08/21) Miller welder has two receptacles on face It gets fed with two hot legs and a ground . So these receptacles are derived on the secondary side somewhere and protected as such? Protected by
electronics on the secondary and no current is traveling on ground back to the panel ? I guess Miller knows what they are doing but it seems a bit weird .

Click to expand...

Are you calling the round pin a ground or the wide slot a ground ?

On a properly connected circuit, the wide slot is neutral, not ground. It is a current carrying wire. The circuit box that originates that branch (not
intermediate boxes) will have that neutral bonded to actual earth ground. U shaped hole is connected to the green, or bare wire will be connected to
that same earth groundway back at the original service entry. Its purpose is to provide a alternate path to ground from a tool with a short to the tool
body, or failed internal components that are no longer connected to neutral. Jim

The primary reason to
Bond that white neutral load current carrying conductor to earth/ground .
Reason Is to hold that load current carrying conductor at or near ground potential .