Silv14
New User
- Location
- Oregon, USA
- Occupation
- Fabrication
Hello,
I'm redoing the wiring in my shop to have a safe updated electrical supply, and I've become a bit confused about where you derive a ground for a 120v single phase subpanel from a 4-wire 3-phase 'high leg' Delta main.
For a little background, the building is from the 50s (which I'm sure you could deduct from the 4-wire delta,) and it had a whole mess of several different fuse boxes (some 3-phase, some single-phase, some 3-ph converted to single-ph, and a whole lot of dust and corrosion between them) along with one 120v sub panel, and another 120v sub panel in a different part of the building, all fed from a honking 3-ph 150amp breaker acting as a main disconnect. I'm using the building for automotive fabrication along with machining, so I have several 3-phase motor loads, and only had one 3-phase fuse box. I upgraded to a Siemens MLO 200amp, 24 spaces, and used the 150amp main breaker to feed that load center.
Now I was beginning to start rewiring in some of my circuits, and I got a bit dumbfounded on where the ground wire ties in to the system. I can't seem to find a straight answer for this. Do I need to run a secondary wire to the neutral lug from the main breaker enclosure, or do I just tap into the neutral bus twice? Or do I need to corner ground one of the legs? There appears to be several bare ground wires already going to the neutral terminal in the main breaker enclosure.
Additionally, I found some mention where it says the NEC does NOT want you to install 1-ph circuits in a 3-ph panel. Is that the case? I'm aware of the 208v Line-B (in my case) to Neutral factor, and that I would have to skip these positions in the box should I place a 1-ph circuit. If it is indeed illegal to power 1-ph 120v circuits from the 3-ph panel I can always add a subpanel for those circuits.
I can post photos as well if that's helpful.
I plan to have all of my work inspected to ensure legality at the end of the project.
Thanks in advanced to all of you sparkies.
I'm redoing the wiring in my shop to have a safe updated electrical supply, and I've become a bit confused about where you derive a ground for a 120v single phase subpanel from a 4-wire 3-phase 'high leg' Delta main.
For a little background, the building is from the 50s (which I'm sure you could deduct from the 4-wire delta,) and it had a whole mess of several different fuse boxes (some 3-phase, some single-phase, some 3-ph converted to single-ph, and a whole lot of dust and corrosion between them) along with one 120v sub panel, and another 120v sub panel in a different part of the building, all fed from a honking 3-ph 150amp breaker acting as a main disconnect. I'm using the building for automotive fabrication along with machining, so I have several 3-phase motor loads, and only had one 3-phase fuse box. I upgraded to a Siemens MLO 200amp, 24 spaces, and used the 150amp main breaker to feed that load center.
Now I was beginning to start rewiring in some of my circuits, and I got a bit dumbfounded on where the ground wire ties in to the system. I can't seem to find a straight answer for this. Do I need to run a secondary wire to the neutral lug from the main breaker enclosure, or do I just tap into the neutral bus twice? Or do I need to corner ground one of the legs? There appears to be several bare ground wires already going to the neutral terminal in the main breaker enclosure.
Additionally, I found some mention where it says the NEC does NOT want you to install 1-ph circuits in a 3-ph panel. Is that the case? I'm aware of the 208v Line-B (in my case) to Neutral factor, and that I would have to skip these positions in the box should I place a 1-ph circuit. If it is indeed illegal to power 1-ph 120v circuits from the 3-ph panel I can always add a subpanel for those circuits.
I can post photos as well if that's helpful.
I plan to have all of my work inspected to ensure legality at the end of the project.
Thanks in advanced to all of you sparkies.
