Electrical Question - New Detached Workshop, 100Amp Subpanel

[Adam Trombello]

You absolutely do want a ground wire connecting both panels, even with ground rods at the sub. Not only is it required, but all sorts of weird things will start to happen with separate grounds-like all the voltage jumping over to one bush bar so that you have nothing on one side, and 220 on the other in the subpanel.

I wonder what their thought on a ground going back to the main is. And how would you have problems with voltage spikes and weird things happening? Youre establishing the same thing by pounding rods out there. The neutral is going to carry any of the unbalance current back.

"....like all the voltage jumping over to one bush bar so that you have nothing on one side, and 220 on the other in the subpanel."
Are you talking about the voltage on each phase? Because there will always be 120v give or take present on each phase. Correct me if I'm wrong.

[Lewis Anderson]

Google "grounding vs bonding" if you are truly interested. There is a lot of information already out there so no need to clutter up this thread further.

[Julie Moriarty]

Good grief, how many different ways can you "ground" (provide an earth return path for current) a panel?!

Of all the different facets of working with electricity, I've found grounding to be the one that brings about the most debate. Most inspectors will require a single ground source for a single service. All sub panels that are fed off that service get their ground from that service. It's the way I was taught to do it and. based on what I've learned over the years, the only method that should be used. But as I mentioned above, there are some inspectors who require more than one ground source and even though there's evidence to prove that can cause problems, they insist that's the way to do it. If you want your work to be approved, you have to accept the "fact" the inspector is always right.

I think the reason grounding methods are so often debated is because it's not entirely contained within insulated materials and devices and therefore we lose control of it. At that point, the flow of electricity becomes as unpredictable as the path of lightning.

[Richard Kulesa]

Great information, perfect, thank you!
I'm going to go with #2 (and #6 for ground).

This is incorrect. You need both ground rods and a ground wire back to the main. With the neutral and ground not bonded(which is correct) at the sub-panel you basically have no short circuit protection. Thus you need a ground path back to the main where the neutral and ground are bonded. Here is an illustration with code references.

[Adam Trombello]

While youre at it, you might want to consider running a 3-way for garage out lights or floods and a low-voltage wire for detach garage door opener in the house

[Tom M King]

http://www.esgroundingsolutions.com/...in-a-sub-panel

http://www.city-data.com/forum/house...ng-160v-3.html

[Adam Trombello]

http://www.esgroundingsolutions.com/...in-a-sub-panel

http://www.city-data.com/forum/house...ng-160v-3.html

Separating neutrals and grounds in subpanel - completely understandable, you don't want current to travel back on ground wire.
Running a ground wire back to the main ground source with a ground source at detached building - I don't get it.


Lewis Anderson, I will have to do a little research on grounding and bonding

[Keith Outten]

My shop has its own service and meter base. I would not have it any other way.
.

[Mike Heidrick]

Keith, Many place do not let you have a second meter base on your primary residence property at all and those that do many time require you to pay commercial rates for the second service.

[Tom M King]

This is a good one, with pictures for each example of being done improperly:

http://www3.ambest.com/DPSDirectoryS...shx?mmid=12761

Be sure to read page 8.

[David L Morse]

This is a good one, with pictures for each example of being done improperly:

http://www3.ambest.com/DPSDirectoryS...shx?mmid=12761

Be sure to read page 8.

Excellent reference! You're right, page 8 is the key, especially the first sentence of item 2. This is exactly the reason for the separate ground wire to an outbuilding. That sentence could be presented more in layman's terms by replacing "clear ground faults" with "cause the breaker to open on a circuit with a short from hot to ground".

[Keith Outten]

Keith, Many place do not let you have a second meter base on your primary residence property at all and those that do many time require you to pay commercial rates for the second service.

Mike,

I figured that a second service might not be an option in some localities but thankfully its not a problem in my area. It didn't cost me a cent to have my shop service installed and now that my shop is a commercial business it makes it easy to report the electrical bills on my business expenses and track them for taxes.

[Richard Yeskoo]

I have a service pole about 300 feet from house and want to build shed next to pole. Any suggestions for tapping off pole service and not running through house panel?

[Lewis Anderson]

I have a service pole about 300 feet from house and want to build shed next to pole. Any suggestions for tapping off pole service and not running through house panel?

Is there a disconnect at the pole or just a meter?

[Rollie Meyers]

It used to be OK to run a 3-wire feed to a outbuilding if there were no parallel paths like a metallic waterline & treat it like a 2nd service, drive a ground rod or use another allowable grounding electrode listed in art. 250, now a 4-wire feed is required and ground rods, a Ufer, & if metallic underground water piping is present at the building it has to be used.

In the early 1990's I used a 3-wire feed out to the building that my shop was attached to in 1993, in 1994 the service on the house was changed & the feeder cables were removed to relocate the conduit into the new panel & pulled back in, I still regret not going to a 4-wire feed & still may do so even though it was compliant at the time.