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Old 03-11-2009, 08:21 AM   #1
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3-wire 220V


Hello:
First of all, I'm a carpenter, not an electrician. I'm planning to build a detached garage. When the electrician came by to scope out his part of the project, I suggested that he tap into a sub-panel in the basement for the garage power. This sub-panel was wired about 12 years ago by a licensed electrician - but we never pulled permits for the work( i.e. it wasn't inspected ). When the house was built there was a 3-wire 220V line for the electric range. When we changed the location of the range, they left the wire in place. When they wired the sub-panel in the basement, they used that wire as the feed, drove a copper grounding rod outside, and attached ground wire from the rod to the panel. I assume that sub-panels need 4-wires or else they would have stayed with the 3-wire.

The electrician tells me that's not code and that he's never seen anything like this before. He says it may have been code 12 years ago, but it isn't today.

What I need to know is - is this safe? I know I should get them to pull a new 4-wire 220V at some point, but I'm a little freaked out at whether this is an immediate issue or not.

By the way, the electrician decided to tap into the main panel for the detached garage.

Thanks,
Mike

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Old 03-11-2009, 08:26 AM   #2
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3-wire 220V


Depending on your area, depends on what year of NEC that they are following. Sounds like you need a new electrician, due to not clear on his codes and what year the panel falls under. If he wants to repull, then that means following the latest codes, not Grandfathered like it is now.

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Old 03-11-2009, 09:57 AM   #3
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3-wire 220V


Thanks, Greg. From what I can tell, the sub-panel installation meets code from 1997 but wouldn't pass for a new installation today. If that's the case, I feel a little better about the safety issue.
Thanks,
Mike
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Old 03-11-2009, 10:32 AM   #4
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3-wire 220V


I believe Greg is mistaken. A 3-wire subfeed was only legal for detached buildings. A subpanel in your basement would have always been required to have a 4-wire feed, no matter what Code year it was installed under. So your new electrician is incorrect about it being legal in 1997. It was illegal in 1997, 1987, or 1947.

In other words, the original installation is/was illegal and your new electrician is right. He did the right decision by not making a bad situation worse by pulling power from that panel. How dangerous is it? Well that depends. It could be relatively safe, or wildly dangerous, depending on exactly how the panel was wired. The safe thing to do, while you already have the check book out and have construction going on, would be to go ahead and bring the basement subpanel up to code.
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Old 03-11-2009, 10:50 AM   #5
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3-wire 220V


I'm in total agreement with Inphase. As I understand you, your electrician of the past used the 3 wire range branch circuit as the wiring method to power your sub-panel. This sub-panel is in the same dwelling with the service equipment. If so this was a code violation.... sub- Panelboards that are in the same dwelling with the service equipment must have 4 wire feeders...H-H-N-Ground. The simple reason for this is in the event of an open neutral between the service equipment and the sub-panel you will still have fault protection via the equipment ground of the feeder and your breakers in the sub-panel will still be able to trip even though you have lost your neutral between panels.
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Old 03-11-2009, 02:18 PM   #6
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I've never rn into a situation like this, but I wonder if your NEC would allow the ground to be run externally from the sheath of the cable? Or must it be inside?
Here in Canada I have seen where an external ground was run, as part of an up-grade!
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Old 03-14-2009, 11:50 AM   #7
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Originally Posted by Wildie View Post
I've never rn into a situation like this, but I wonder if your NEC would allow the ground to be run externally from the sheath of the cable? Or must it be inside?
Here in Canada I have seen where an external ground was run, as part of an up-grade!
Sorry, but you cannot do this and be compliant. The ground must be included in the cable or pulled inside a conduit. Or a metal conduit can be used as the ground.
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Old 03-14-2009, 12:01 PM   #8
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3-wire 220V


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Answers based on the 2008 & 2011 NEC.
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Old 03-14-2009, 01:39 PM   #9
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Nice pic! What I had in mind was a case where non-metalic sheathed stove cable was in place, but was lacking a ground, so was wondering if an additional ground could be run as a retrofit!

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