Workshop Wiring

rick7938 · 07-28-2007, 08:00 PM

My neighbor has a workshop that was wired by a "handyman" that he had working for him years ago. I don't know anything about electricity except to leave it alone, so I am asking a question on his behalf. When the workshop was wired, it was supposed to have a 6-gauge 3-wire with ground feeding a sub-panel in the workshop. The handyman wired it with 6-gauge 2-wire with ground using the black and white wires as hot and the ground wire as neutral and ground. It has seemed to work fine for 10 years, but what kind of problems could this possible cause for him in the future? He is concerned about fire hazards or shock.

Thanks for any feedback.

NCPete · 07-28-2007, 08:07 PM

I am not aware of code implications from 10 years ago. If it was run correctly, he is as safe today as he has been for the last 10 years.

Bryan S · 07-28-2007, 10:04 PM

This does sound like a potentially dangerous situation. If I am reading your post correctly he is using the black as one of the hot legs and the white as the other hot leg ( 220 volts between the black and white wires). The neutral (should be white) is a grounded conductor meaning current (amps) flows through the neutral back to the grounded terminals in the main panel. The ground is not intended to carry current and in alot of cases the ground wire is a bare copper wire. It is there for saftey reasons. If there is a short circuit in any equipment it carrys the current to ground so the current doesn't travel through us.

I am not a licensed electrian but I do know code does not allow the ground wire to be used as a neutral, it has to be 2 seperate wires. It also does not allow the ground and neutral to be tied to the same terminals in a sub panel. I'm going to guess that the person that did his wiring for him did it this way to save money aka cutting corners. If it were me I would have it done right. If your neighbor doesn't doesn't want to or doesn't know how to do it himself I strongly recomend he find a licensed electrician to do it.

I dont mean to sound like an alarmist its just that electricty is nothing to play or take chances with and his concerns are justified. I hope I explained things good enough for you if not I think we do have some electritians on here that can explain it better.

NCPete · 07-28-2007, 11:09 PM

not uncommon for many 220 appliances to use 2 hots and a combined neutral/grounding wire. I install 'em like that nearly every day, depending on the house. On an appropriate (for the era) wire, the white may be labeled with a piece of black tape to identify it as a hot wire. Newer homes, and mobile homes since LONG time ago, are (or should be) wired with 2 hots, as well as individual neutral and grounding wires. Bruce (Junquecol) should be able to provide more guidance.

Travis Porter · 07-29-2007, 12:33 AM

If the building is detached he is supposed to have a ground rod as well, at least in Wake County.

NCPete · 07-29-2007, 02:40 AM

Originally Posted by Travis Porter

If the building is detached he is supposed to have a ground rod as well, at least in Wake County.

true, even 10-12 years ago, that was code in Cumberland county... the panel needs to be grounded, and not to the 'mother'(?) panel and its ground

rick7938 · 07-29-2007, 06:42 AM

Thanks for the info, guys. Can the panel be grounded to a water pipe in the building or does it have to be a driven rod?

pcooper · 07-29-2007, 09:51 AM

When I did my shop I was required to run four wires from my main panel to my shop panel. Two were hot, one was neutral, the fourth (green) was panel ground. I also had to run a rod into the ground at the shop that the green wire attached to. I am told that you can have shock from shorted wires if not grounded that way, such as a shorted 220 motor winding or something along that line. I did have another shop that was three wires, two hot and one neutral and didn't have a problem for more than 18 years, but I guess I never had a short either.

cpowell · 07-29-2007, 10:52 AM

Is the shop detached? Is there a conductive path between the shop and house (copper water pipes, etc)?

If the shop is detached and there is not a conductive path between shop and house then you could run three wires from the main panel to the shop - L1, L2, Neutral. A grounding electrode (rod) must be driven at the shop adjacent to the panel. The grounding electrode is connected to the ground bar in the panel. The neutral and grounding bars in the shop subpanel MUST be joined together. This is the way my shop is set up. Perfectly acceptable.

You can always run 4 wires, L1, L2, Neutral, Ground. You would still drive a ground rod at the shop panel and connect to the ground bar but would NOT connect the ground and neutral bars to each other in the shop panel.

Here'a a link that shows different ways to power a detached shop. http://www.selfhelpandmore.com/homew...garageshow.htm

Chuck

Mtnman · 07-29-2007, 03:16 PM

I agree with Bryan. You have a disaster looking for a place to happen. If you ever sell your house and shop I feel it may not pass inspection.
I wired my whole shop and house. I provided both 220 V and 110 v on separate wires that were appropriate size and the number of conductors for hot and ground wires.
I really think that it would be very easy to get mixed up about which wire was for 110 v and which was for 220 v when installing a new outlet.
My advice is to reconnect the existing wires to 110 v according to existing code, and add another breaker to the power panel with new 4 wire (2 conductor & 1 neutral with a bare wire ground) to provide 220 v where needed.
By the way it's a very good idea to use 220 v on any shop machine that allows you to use either 220 v or 110 v. You will notice it will run much better under load, and only pull 1/2 of the amps through the wire.

cpowell · 07-29-2007, 10:26 PM

Originally Posted by rick7938

Thanks for the info, guys. Can the panel be grounded to a water pipe in the building or does it have to be a driven rod?

If your neighbor has a metal water pipe that runs between the house and the shop then he is REQUIRED to use a 4-wire feed from the house panel. A metal water pipe between house and shop is a "metallic, non-current carrying path".

If you look at this link, about 80 percent of the way through, it spells out the exact requirements for detached shop panel wiring in layman's terms. I have looked at both scenarios for wiring a detached shop with an underground feed and believe them to be accurate. http://www.selfhelpandmore.com/homew...garageshow.htm

Please note the "rules" for using a 3 wire feed, and also the difference in shop panel Neutral and Ground bar treatment depending on whether a 3-wire or 4-wire feed is used.

Grounding electrode at shop panel is required either way you go.

There is also a description of how many breakers are allowed in the subpanel, depending on whether the subpanel has a main breaker or not. It's a good source of info.

Chuck

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