120 v circuit in a 240 v 3 phase panel, no neutral

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Stevenfyeager

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United States, Indiana
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electrical contractor
I do almost all residential. But I need to add a 120 v circuit in a 240 v, 3 phase panel in a store. I know that I can install a single pole breaker on one of the two bus bars on either of the two sides and get 120 volts. But in this panel, no neutral wire was run from the gutter into the panel, only 3 hot phase wires. There is a ground bar in the panel, but no wire to it. By connecting my 120 v neutral wire (and ground wire) to this ground bar, wouldn't I be putting a neutral load on that equipment grounding system? (There is already one other 120 volt circuit wired this way.) I know that the conduit can be the grounding electrode. But I am used to residential panels where a neutral wire is present that goes back to the power company. Thank you.
 
Stevenfyeager said:
I do almost all residential. But I need to add a 120 v circuit in a 240 v, 3 phase panel in a store. I know that I can install a single pole breaker on one of the two bus bars on either of the two sides and get 120 volts. But in this panel, no neutral wire was run from the gutter into the panel, only 3 hot phase wires. There is a ground bar in the panel, but no wire to it. By connecting my 120 v neutral wire (and ground wire) to this ground bar, wouldn't I be putting a neutral load on that equipment grounding system? (There is already one other 120 volt circuit wired this way.) I know that the conduit can be the grounding electrode. But I am used to residential panels where a neutral wire is present that goes back to the power company. Thank you.
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You can't, by code, run a line to neutral circuit from a panel that doesn't have a neutral. The one circuit that you saw is not correct. BTW, the conduit can be the equipment grounding conductor (EGC) but not the "grounding electrode" (GEC).

There should be a neutral at the main, you would have to run it to the panel you want to get the 120V circuit from.

Note: You probably have a 240V Delta system with a high leg. You would have to be careful not to use the high leg for the 120V circuit even if there was a neutral present.
 
Do Non-Contact Voltage Sensors (Tic Tracers) even sense properly wired neutrals when energized, much less such objectionable currents on grounding paths, raceways, panels, or equipment acting as a neutral return path?

250.6 Tells us its illegal, and how to remove it, but not how to detect it. A clamp meter is the only tool that comes to mind.

When such bootleg circuits are under load with cabinets locked, and raceways are larger than our clamp meter, how do we find objectionable current before getting electrocuted?
 
ramsy said:
..When such bootleg circuits are under load with cabinets locked, and raceways are larger than our clamp meter, how do we find objectionable current before getting electrocuted?
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Maybe I should ask a plumber?
 
ActionDave said:
You have it right. You need a need a neutral.
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Your typo aside one can either pull one from wherever it is available in upstream distribution or depending on situation could be less cost to separately derive it. They do that quite often in machines that only have three phase conductors for supply yet still have 120 volt controls within them.
 
kwired said:
... could be less cost to separately derive it. They do that quite often in machines that only have three phase conductors for supply yet still have 120 volt controls within them.
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Very true, I've even had to do that with 208V panels when the neutral was not brought out.

What is the 120V power needed for? If it's just control power or something like that, just add a control power transformer.

One thing you CANNOT legally do is connect one phase and ground. Even though it might technically read 120V (from two of the phases), you will have turned your EGC into a current carrying conductor, and that is illegal.
 
ActionDave said:
I didn't see see that typo.
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I had to read it three times before I caught it. My brain just skipped over it. Kind of like

screen-shot-2013-08-01-at-10-28-53-am.png
 
Stevenfyeager said:
I do almost all residential. But I need to add a 120 v circuit in a 240 v, 3 phase panel in a store. I know that I can install a single pole breaker on one of the two bus bars on either of the two sides and get 120 volts. But in this panel, no neutral wire was run from the gutter into the panel, only 3 hot phase wires. There is a ground bar in the panel, but no wire to it. By connecting my 120 v neutral wire (and ground wire) to this ground bar, wouldn't I be putting a neutral load on that equipment grounding system? (There is already one other 120 volt circuit wired this way.) I know that the conduit can be the grounding electrode. But I am used to residential panels where a neutral wire is present that goes back to the power company. Thank you.
Click to expand...

As someone else said, it has to be a high leg service for this to even be possible. If it's an ungrounded 240V three phase service with no center tap between two of the phases you cannot get 120V from it without adding a transformer to derive the neutral.
 
ggunn said:
As someone else said, it has to be a high leg service for this to even be possible. If it's an ungrounded 240V three phase service with no center tap between two of the phases you cannot get 120V from it without adding a transformer to derive the neutral.
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He said there was an existing 120 volt circuit with neutral landed on EGC bus - with metal raceway completing at least the path to the next upstream panel, so it has to be a system with 120 volts to a grounded conductor if that actually worked.
 
kwired said:
He said there was an existing 120 volt circuit with neutral landed on EGC bus - with metal raceway completing at least the path to the next upstream panel, so it has to be a system with 120 volts to a grounded conductor if that actually worked.
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:thumbsup:
Most likely would be a high leg delta with the neutral simply not carried to the panel.
 
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