Wiring a Shop

My son has built a large shop with living quarters above. He plans to wire from his home breaker box and run an underground power supply approximately forty foot. Living quarters is for future use, so it's wiring will be done later. I have advised him to use GFCI Breakers throughout his shop.
Now---Have I got this right---I know this has been discussed many times with mixed advise, but I want to do this right.
I plan to install the shop breaker box and "bond the box". I will then hook all the neutral wires to the neutral connection bar and connect all the bare copper" ground" wires to a separate bar that will be connected to an outside ground bar, which we will install, close to the box.
It has been a while since I have done this and I would appreciate any correction or advise.

4 wire feed, do not bond, no ground rod.

USA1 is right, bonding should be at point of entry only.

and point of entry in this case is the main breaker box nearest the meter.

That is what I would think, shop would be fed from breaker in that panel, run 4 wires.

True, this has been often discussed,,,,,, and true with mixed advice, some which is professional, educated, correct and current NEC code compliant, other that is Billy Bob or Bubbas (wired their own house over a case of beer and by golly it works) which is incorrect and potentially hazardous, your money, your life, your risk and your choice which to follow.

Here is my advice (retired Electrical Engineer and not current on latest codes as the many fine still practicing professional electricians here) feel free to take or leave it. NO WARRANTY it may or may not be correct (too long retired), I'm NOT saying it is or it isn't, so there lol



If you're wiring a separate buildings 120/240 volt Single Phase Three Wire Sub Panel fed by a Main Panel in the house, under the latest code as far as I know, NO WARRANTY BILLY BOB so don't have a calf if its incorrect!!


Run 4 wires out, Two Ungrounded Hot Phase Conductors ,,,,,One GrounDED Conductor (Neutral),,,,,,,One Equipment GroundING Conductor

At the remote sub panel (Unlike at the main) keep the Ground Buss (Green and Bare equipment GroundING Conductors) and the Neutral Busses (Whites) separate and electrically isolated.

The panels metallic box/tub, same as any other non conducting metal enclosures, gets connected to the Ground Buss

Any buildings electrical service, as far as I know (unless code has changed), requires earth grounding to a proper Grounding Electrode using a Grounding Electrode Conductor (I used No. 4 bare copper). A Grounding Electrode may consist of buried conductive water pipes or structural or foundation steel or what are called "made electrodes" such as copper rod or rods driven into the earth. In our jurisdiction we bonded all readily available grounding electrodes and if no other were present we used "made" electrode(s). Check with local authority and utility provider. Since this is a sub panel in a remote separate building the Grounding Electrode via the Grounding Electrode Conductor is connected to the Ground Buss.

The wire size to the remote location depends on the wire used, the enclosure and/or direct burial or aerial etc. etc., and the distance and amperage.

SO THERE now feel free to go with "mixed advice" or educated experienced advice from professionals, or advice from lay persons or Billy Bob and Bubba or whom you please. DO NOT NECESSARILY GO WITH MINE although I practiced this for years as an engineer, I been retired too long. Electrical and legal questions often draw everyone out of the woodwork all of whom are experts (although a few indeed are) you know, so my final advice is to consult with local authority and the utility provider and go with competent professional advice versus lay persons.

Nuff said

John T

Describe this some more. 4 wire would be 2 hot wires for 220 volt, a neutral and ground. Wouldn"t you run the 2 hot and neutral wires from the existing house and for the ground you would drive a ground rod at the new building?

You say "no ground rod" If that's so the darn NEC has changed since I practiced (or at least in our jurisdiction) grrrrrrr as back then each buildings electrical service had to be connected to a GroundING Electrode. Seems strange that isn't still required for a separate building (unlike a sub in the same building)???

Thanks, John T

Under past codes you could indeed just run 3 wires out (2 Hots and 1 Neutral) and earth ground the Neutral at the remote panel, like done in the main at the house. Under later codes, you run 4 out (2 Hots, 1 Neutral, 1 Equipment Ground). True either will work but also true the new system represents an improvement in safety.

Feel free to wire anyway you please

John T

I am thinking this is the same building.

My son's new shop is located approximately ten foot from his existing home. In the future, the new shop will be an addition to his home and connected with a hallway allowing entry to shop and steps leading upstairs. So, it will be same building, but for now, it is separate.
Now--If running four wires to the shop, where will the connection be made in the home panel for the fourth wire?
BTW I do know the purpose for this fourth wire.

Same building does NOT require another ground rod, but if separate it does (or did when I practiced at least ).

Fun sparky chattin

John T

Yup, that is why I did not specify a ground rod. I think his residence is upstairs and shop below.

Id wire it as separate then.....

"Now--If running four wires to the shop, where will the connection be made in the home panel for the fourth wire?"

The two hots come off a 2 pole breaker, Neutral off Neutral Buss, equipment Ground off Ground Buss. In some main panels theres only a single common Ground/Neutral Buss so both Neutral and Equipment Ground out to sub come off it.

John T

Looks like he just posted above its 10 feet apart, so Id go with that as separate and yes such requires another Grounding Electrode at the separate building IIffffffff that's the case lol)??

Fun chat

John T

[b:5f35a5d64b]In some main panels theres only a single common Ground/Neutral Buss so both Neutral and Equipment Ground out to sub come off it.[/b:5f35a5d64b]

I have no problem with running the fourth wire, but what would be the purpose if it is connected to the same buss in the main home panel?
Please bear with me--I am trying to learn and do it right.

[b:5752ec2e30]In some main panels theres only a single common Ground/Neutral Buss so both Neutral and Equipment Ground out to sub come off it.[/b:5752ec2e30]

I have no problem with running the fourth wire, but what would be the purpose if it is connected to the same buss in the main home panel?
Please bear with me--I am trying to learn and do it right.

No problem Jiles, your good questions show youre trying to learn and do it right.

QUESTION "I have no problem with running the fourth wire, but what would be the purpose if it is connected to the same buss in the main home panel?"

MY PROFESSIONAL OPINION No warranty it may be right or wrong and Im not saying its either, feel free to take it or leave it as you choose


The Equipment GroundING Conductor is designed to carry ONLY Fault Current, NEVER normal Neutral return current. That's why its a dedicated and isolated conductor soley to return fault current.

The Neutral is a Grounded yet live current carrying conductor and you see its insulated and I bet you would walk up to it and peel off the insulation and touch it when the appliance is on cuz you may be placing your old ticker in a parallel path with a live current carrier.

The Equipment GroundING conductor is carried out to the sub and is ONLY there to conduct fault current and that's why at the sub its NOT tied to the Neutral. The Neutral is for carrying all the normal return current AND THE TWO SHOULD NOT BE MIXED AND MATCHED AND SUBSTITUTED otherwise the ground may be carrying return current (ONLY supposed to carry fault current).

The equipment GroundiNG Conductor is often wired to the outer conductive metallic case of a tool or appliance and you touch that. Would you want to touch the insulated Neutral that's hot and carrying current??? NOOOOOOOO but if you mix n match and sub one for the other that can happen. Also the wrong set of accidental shorts or opens
could end up energizing the case of a tool if Neutrals and Grounds are mixed n matched.

Neutral is insulated and carries return current Ground is bare and may be wired to a tool case so do not mix n match and substitute one for the other.

When you run 4 wires out to a sub the Neutral carries ONLY normal return current while Ground is dedicated to carry ONLY fault current.

Nuff for now were headed to Square Dance Lessons where each year we teach the new students, I will check back tomorrow if more questions

John T

(quoted from post at 23:16:46 06/10/14) No problem Jiles, your good questions show youre trying to learn and do it right.

QUESTION "I have no problem with running the fourth wire, but what would be the purpose if it is connected to the same buss in the main home panel?"

MY PROFESSIONAL OPINION No warranty it may be right or wrong and Im not saying its either, feel free to take it or leave it as you choose


The Equipment GroundING Conductor is designed to carry ONLY Fault Current, NEVER normal Neutral return current. That's why its a dedicated and isolated conductor soley to return fault current.

The Neutral is a Grounded yet live current carrying conductor and you see its insulated and I bet you would walk up to it and peel off the insulation and touch it when the appliance is on cuz you may be placing your old ticker in a parallel path with a live current carrier.

The Equipment GroundING conductor is carried out to the sub and is ONLY there to conduct fault current and that's why at the sub its NOT tied to the Neutral. The Neutral is for carrying all the normal return current AND THE TWO SHOULD NOT BE MIXED AND MATCHED AND SUBSTITUTED otherwise the ground may be carrying return current (ONLY supposed to carry fault current).

The equipment GroundiNG Conductor is often wired to the outer conductive metallic case of a tool or appliance and you touch that. Would you want to touch the insulated Neutral that's hot and carrying current??? NOOOOOOOO but if you mix n match and sub one for the other that can happen. Also the wrong set of accidental shorts or opens
could end up energizing the case of a tool if Neutrals and Grounds are mixed n matched.

Neutral is insulated and carries return current Ground is bare and may be wired to a tool case so do not mix n match and substitute one for the other.

When you run 4 wires out to a sub the Neutral carries ONLY normal return current while Ground is dedicated to carry ONLY fault current.

Nuff for now were headed to Square Dance Lessons where each year we teach the new students, I will check back tomorrow if more questions

John T

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Now I can understand that, excellent explanation---THANKS----

As a retired contractor, I believe you have a Resturant sized can of worms, adressing a living area over a shop. For building permit purposes, I would call it a garage, rather than shop, but if you son hangs a shingle out front for shop work, the wireing you would have to use will change drastically, and all walls, ceiling, doors, etc, will become real construction issues for him, as they will have to be fire rated. He will also need propper outside egress from the living quarters, and perhaps even an engineered sprinkler system.
The both of you better put a lot of thought, and ask a lot of questions to your local code enforcement office, before you build yourselves into a financially disasterous situation.
Just food for thought,the rules have changed, I'm glad I am no longer in the building business.
Loren, the Acg.

Just adding to the fray but in my area if you elect
to use grounding rods at the new structure, you
actually need to drive 2 rods at least 6 ft apart
and use a continuous piece of #6 ground wire . The
wire leaves the panel hits one rod continues to the
next and then back to the panel. Purpose being a
severed ground wire still enables a path to ground
via the unsevered wire.

have been working with an electrcal contractor this
past few weeks installing new circit breaker panels
into a trailer park and every panel he has driven a
rod into the ground and hooked up a ground wire to
it and the grounding bus in the panel as well as
the feed wire has its own ground wire from the
source panel as well told me it was code that all
panels are grounded indepent of their source
suypply

(quoted from post at 15:18:54 06/10/14) USA1 is right, bonding should be at point of entry only.

Click to expand...

Sub panel , pony panel neutral bar is supposed to float isolated from ground . Remove the bonding screw.
Two eight foot ground rods at least 10 feet apart . Joined to each other and to the panel ground bar with #6 copper.
Residence requires at least a 100amp panel to be legal.

Here is a view of the Garage / Home.