# Grounding to Metal Box



## CaptChaos (Aug 10, 2009)

Ok...so I have a dumb, newbie question. Is it allowable (or advisable) to run a ground wire from an outlet panel to the metal junction box? 

I always was under the impression that you needed a ground that run to a grounding rod or metal pipe. I have a house built in 1915 which doesn't have grounding wiring -- is grounding to a junction box an alternative if your present budge doesn't allow proper grounding?


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## AllanJ (Nov 24, 2007)

The various junction boxes (and outlet boxes), if metal, are supposed to all be grounded to the breaker panel either by (metal) conduits carrying the various wires or by a ground wire inside each multi-wire cable.

The system is not complete (or code compliant) until a ground wire is added from the breaker panel to a ground rod or to a metal water pipe exiting the house underground for the water main or well.

In addition the "neutral" from the utility pole down through your meter and to the first switch or breaker that controls the entire house doubles as a ground. If this first main disconnect is not at the main panel then a ground wire separate from the neutral must run from that main disconnect to that "main" panel which is really a subpanel without the first main disconnect switch.

I'm not sure about the size for these last two ground wires; I think #6 copper is the minimum.


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## hayewe farm (Mar 15, 2009)

If the junction box is not grounded running a wire to it would have about the same affect as hanging it out the window, none.


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## Jim Port (Sep 21, 2007)

Running an independant grounding wire to the receptacles is the same amount of work as running new cables with a ground.

If the budget does not allow the whole house to be upgraded just run new circuits where the grounding is needed.


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## WaldenL (Jan 9, 2009)

OP, can you clarify what you're asking? Are you asking if you can install a 3-prong (grounded) outlet in a metal box in the wall, hook the metal box to the grounding screw on the outlet and have a grounded outlet? The answer is, it depends. *IF *the metal box is grounded then yes, but I think you're saying that there is no grounding wire (nor metal BX cable sheath) running to the metal box, right?. If that's the case, then hooking the grounding screw to the metal box will do you no good since there would still be no path back to the main breaker box.

If you're asking if you could run a separate (new) grounding wire to the metal box to ground it. Then electrically it would work, but it wouldn't be anywhere near code. And if you're pulling the wire anyway, just pull a new run. I know budget is always an issue, but a spool of 14/2 w/ground won't run you much more at all than the run of bare copper wire, and then it's done right. How long a run? 50' of 14/2 will cost you about $15. Skip starbucks for a few days and do it right.


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## J. V. (Jun 1, 2007)

No. You cannot run a separate ground wire to the box.


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## CaptChaos (Aug 10, 2009)

AllanJ said:


> The various junction boxes (and outlet boxes), if metal, are supposed to all be grounded to the breaker panel either by (metal) conduits carrying the various wires or by a ground wire inside each multi-wire cable.


So, I think I have finally figured out why, despite no visible round wires, my outlets register as grounded when tested with a three-prong outlet tester. As AllanJ points out above, metal conduits can also act as a ground -- I think this is what is happening in my case, so I was happy to find that I am already properly grounded -- is this to code?


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## spark plug (May 5, 2009)

CaptChaos said:


> So, I think I have finally figured out why, despite no visible round wires, my outlets register as grounded when tested with a three-prong outlet tester. As AllanJ points out above, metal conduits can also act as a ground -- I think this is what is happening in my case, so I was happy to find that I am already properly grounded -- is this to code?


Yes! As long as there is Ground Continuity back to the panel. Regardless of the method. It could be metal Conduit. (originally, there was no EMT) Armored cable or Non-Metallic cable, with a bare, Grounding wire inside. (No matter what):yes::no::drinkon't Drink and Drive, Ever!!!


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## Billy_Bob (Sep 11, 2008)

Basically with old homes without grounds, you need to start by upgrading/replacing the main electric panel(s) so they are properly grounded to current code. (Electrician thing typically.) Then replace the house wiring with grounded wiring as necessary or as the budget allows.

And you would ground metal junction boxes and metal electrical boxes along the way.

The problem with old electric panels is they may not have a ground bar. Or the ground connection may have been cut/disconnected. Or the panel may be grounded to a water pipe and someone has since replaced the main metal water pipe with plastic water pipe (no ground).


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## spark plug (May 5, 2009)

*Issue of grounding boxes in old wiring.*



Billy_Bob said:


> Basically with old homes without grounds, you need to start by upgrading/replacing the main electric panel(s) so they are properly grounded to current code. (Electrician thing typically.) Then replace the house wiring with grounded wiring as necessary or as the budget allows.
> 
> And you would ground metal junction boxes and metal electrical boxes along the way.
> 
> The problem with old electric panels is they may not have a ground bar. Or the ground connection may have been cut/disconnected. Or the panel may be grounded to a water pipe and someone has since replaced the main metal water pipe with plastic water pipe (no ground).


This, I believe is one of the (if not THE) main reasons that the last few (4) versions of the NEC require dedicated Grounds (green wire) attached to the box and receptacle/switch. Because a lot of existing plumbing pipes are replaced with plastic. And the boxes themselves are plastic. (I'm not saying anything new, but stating the obvious). But until the last Ten years, going back a long time when you installed a light/switch/ receptacle you didn't have to worry about the ground. Especially in NYC where NM cable (Romex) is not permitted for any permanent installations, you would have ground continuity on any properly installed circuit. (No matter what):yes::no::drinkon't Drink and Drive, Ever!!!


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## WaldenL (Jan 9, 2009)

spark plug said:


> Especially in NYC where NM cable (Romex) is not permitted for any permanent installations


I've heard, but haven't checked, that even NYC is starting to allow NM cable in some installations. The times they are a changin'.


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## spark plug (May 5, 2009)

WaldenL said:


> I've heard, but haven't checked, that even NYC is starting to allow NM cable in some installations. The times they are a changin'.


I haven't heard that particular piece of news. But I wouldn't be surprised. Since NYC adopted the NEC (What rules now is the 2005 version) lots of working rules have changed. What's interesting is that in Queens at the border of Nassau County, we have one set of rules on one side of the street and another (with another AHJ) on the opposite side. Eliminate confusion:yes::no: Through Education; (No matter what) :drinkon't drink and Drive, Ever!!!


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