Really dumb electrical question

[Lou Ferrarini]

I am wiring a sub panel for my new shop. I did this before (about 15 years ago), but I just plain forgot this one. The sub will be 220 Volt, with 2 hots, a ground and a neutal. When you wire the 220 volt outlets, do you use the ground or the neutral wire?

[Russ Filtz]

Ground, unless the appliance needs a 120 circuit, then it needs all 4 wires. I would think the outlets would have a green screw which always means ground! Ground is only ground! Basically though once both get back to the main panel they are bonded together and then run out of the panel to the ground rod. So your circuits would work either way, just wouldn't be safe or up to code!

[Todd Bin]

Below is a picture of the subpanel I installed. Hope this helps.

[Todd Bin]

Don't forget that most codes specify that the sub panel can not be "bonded". Which means it has to have the same ground as the main panel. You can not tie ground to neutral in your subpanel.

[Peter Stahl]

Todd, How many amps is your sub? Feed wire doesn't look that big.

[Rick Christopherson]

You need to remove the bonding jumper from the subpanel. This is the bar and two screws I can see at the bottom of the breakers in your picture, and connects the ground and neutral busses together. They cannot be connected together in a subpanel.

[Todd Bin]

The picture is not the final picture. The bond strap is removed. The neutral and ground are not connected now.

I used a 4 AWG wire to go from the main to the subpanel and I have a 60 Amp breaker in the main panel. This is plenty as I will only have at most the lights (4-5 Amps maybe), the Dust Collector (12 Amps) and a single tool on (20 Amps?).

Thanks,

Todd

[Russ Filtz]

Is the bonding jumper thing true for both main lugs and a breakered panel? I thought with main breakered, you kept the bond, not sure though.

[Todd Bin]

I am not a licensed electrician, but it is my understanding that the mian breaker panel should be bonded and if you open it up and use a multimeter you will see connection between ground and neutral. But in the sub panel it is not supposed to be bonded.

Disclaimer: as always you should consult your own electrical code book.

[Todd Bin]

I just had to post the picture with the bonding tie removed.

[Jim Thiel]

OK, now I have a question on Todd's sub; Should there be a ground wire attached to the ground bar? A dedicated wire that runs to ground I mean, not the 12 gauge wires there. It doesn't appear that the ground bar is grounded to anything at the moment.

Thanks for clarity.

Jim

[dan mahler]

In Todd's original pic the ground wire (which should be connected to an 8' ground rod (IMO)) was there, now its not?

[Michael Lutz]

Dan,

The ground wire would only need to be connected to a ground rod if it is located in a seperate building from the main service panel it is being fed from. If they are in the same building the ground should come from the main panel. Todd didn't mention where his subpanel is located in relation to his main panel.

Mike

[Rick Christopherson]

OK, now I have a question on Todd's sub; Should there be a ground wire attached to the ground bar? A dedicated wire that runs to ground I mean, not the 12 gauge wires there. It doesn't appear that the ground bar is grounded to anything at the moment.

Thanks for clarity.

Jim

Jim, if you look at the first picture posted (because it is bigger) you will see that the very top ground wire going to the ground bus is coming from the main load center via the 4/3 (with ground) cable feeding his panel. The size of the ground wire is smaller than #4, which is permitted by code, so you probably didn't notice it.

I forgot who asked this, but there can be only one location in an entire electrical system where the ground and neutral are connected together. This is either the main load center (or in some cases the main disconnect), and all subpanels thereafter must have isolated ground and neutral connections. If there was more than one location where these wires were connected together, then you would have two parallel wires, and as a result, current would flow through the ground wire that is normally supposed to flow through the neutral.

Ground and neutral are not the same, but because they are connected together at this single location, many people think they are the same. Think of it like a roadway. You don't consider two roads being equal just because the have an intersection, right? However, if they shared two common intersections, then they would be the same because you could drive down either road and get to the same location.

[Chris Padilla]

From what I understand and carrying Rick's comments a tad further, the ground (bare or green wire) is there for PROTECTION. Protection to prevent YOU from becoming a part of the circuit should a problem arise. You don't want current flowing thorugh your body--it'll just ruin your day...or life. So in a normal situation where everything is copacetic, jim-dandy peachy keen fine, no current flows through the ground wire (the neutral is the current return wire for the black and red hot wires).