Been reading through a bunch of posts & I have 1 thing I want to confirm before I do something wrong. I'll start by saying Im no electricians. I do know what Im doing & I have an electrician on call just in case. I wired my whole shop & got my final inspection. But since then I've bought a CNC machine that came with a sub panel with all the wires & breakers installed & ready to go. I figure this will be easier to wire up with a single big wire & breaker coming from my main panel, going over the top of my shop to the other side where the CNC machine will be instead of wiring 3 separate circuits. So I know that a sub panel shouldnt have a common neutral & ground so Im used to having a ground bus to separate the 2. This sub-panel wasnt wired that way from the guy I bought it from. I noticed 2 of the plugs are 250v 20amp with no neutral. Just 2 hots & a ground. The other 2 plugs/breakers are regular 220V with 2 hots, neutral, & a ground. Should I pull all 4 of those grounds off the neutral bus & add a ground bus to separate them & just not have the 2 250v plugs with a neutral? I've wired the same plugs to a main panel before so Im used to not having the neutral wire but this sub panel wiring is throwing me off especially since the previous owner didnt have the sub-panel wired with a separate ground bus. Not sure if I should change it. Thanks for the help.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Grounding Sub Panel (Non-Neutral plugs)
- Thread starter Javahead
- Start date
rlitman
Well-known member
The sub panel should have a separate ground bus. Ground wires go to it, and neutral wires go to the neutral bus, just like you figured.
I'll add a 2nd grounding question. I'll also be running a different sub-panel to a detached building. I've added the 2 grounding rods, added a separate ground bus to the sub panel. All I need to do is run the 6 guage ground wire straight to that bus correct? When I wired my shop it was a metal building. I of course ran the ground wire from the 2 ground rods to the meter box & then grounded the neutral/ground bus in the main panel to the box & then the inspector had me run another ground wire from the box up to the roof of my metal building to ground the shop. But all I need to do in this detached shop (which is all wood) is run that ground wire to the box correct?
wyliesdiesels
Well-known member
Thats what I figured so the fact that 2 of the plugs have no neutral doesnt matter.
If the plugs are 250v grounded, then there would be no neutral.
The plugs would need to be rated 125/250v grounded to have a neutral connection.
wyliesdiesels
Well-known member
I'll add a 2nd grounding question. I'll also be running a different sub-panel to a detached building. I've added the 2 grounding rods, added a separate ground bus to the sub panel. All I need to do is run the 6 guage ground wire straight to that bus correct? When I wired my shop it was a metal building. I of course ran the ground wire from the 2 ground rods to the meter box & then grounded the neutral/ground bus in the main panel to the box & then the inspector had me run another ground wire from the box up to the roof of my metal building to ground the shop. But all I need to do in this detached shop (which is all wood) is run that ground wire to the box correct?
You need a 4-wire feeder ran to that subpanel- 2 hots neutral and ground. The neutral bus needs to be isolated. You need to have a separate ground bar that is bonded to the enclosure. The GEC from the rods goes to the ground bar.
All of this is explained on the electrical FAQs sticky at the top of the forum. Theres also pictures. Viewing that first eouldve answered all your questions here.
They are 250V grounded plugs so no neutral. Just making sure I was correct. As stated I have been reading through posts for the last month & I've read through all of the FAQ a few times. I just wanted to confirm that I was understanding it correctly. Thanks for pointing that out.
rodder98
Well-known member
You definitely need to separate the neutral buss bar from the ground bar in your sub panel.. Yes, the 4 grounds should be pulled off of the neutral bar. If there is a ground connector on the neutral bar, going to the panel box, you need to remove it.
Thanks Rodder98. Did that all today but then I realized that I was only leaving 1 neutral wire on the neutral bus & that threw me off. Also the fact that the previous owner of this CNC machine had this sub-panel wired without an isolated neutral really had me thrown off! I've never put those style plugs on a sub panel only a main panel so I just wanted to confirm I wasnt missing anything. Sounds like I had it all done right.
Last edited:
wyliesdiesels
Well-known member
Did you run 4-wires to the subpanel?