Grounding To Metal Box - Electrical - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 10-19-2009, 09:49 PM   #1
Member
 
CaptChaos's Avatar
 
Join Date: Aug 2009
Location: Weehawken, NJ
Posts: 58
Rewards Points: 75
Question

Grounding to Metal Box


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?

Advertisement

CaptChaos is offline   Reply With Quote
Old 10-19-2009, 10:58 PM   #2
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,976
Rewards Points: 2,048
Default

Grounding to Metal Box


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.

Advertisement

__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.

Last edited by AllanJ; 10-19-2009 at 11:07 PM.
AllanJ is offline   Reply With Quote
Old 10-19-2009, 11:00 PM   #3
Member
 
Join Date: Mar 2009
Posts: 780
Rewards Points: 500
Default

Grounding to Metal Box


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.
hayewe farm is offline   Reply With Quote
Old 10-20-2009, 10:18 AM   #4
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 8,048
Rewards Points: 2,894
Default

Grounding to Metal Box


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.
Jim Port is online now   Reply With Quote
Old 10-20-2009, 11:32 AM   #5
Member
 
WaldenL's Avatar
 
Join Date: Jan 2009
Location: Nassau, Long Island, NY
Posts: 349
Rewards Points: 268
Default

Grounding to Metal Box


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. :-)
WaldenL is offline   Reply With Quote
Old 10-20-2009, 02:35 PM   #6
Member
 
Join Date: Jun 2007
Posts: 3,510
Rewards Points: 2,008
Default

Grounding to Metal Box


No. You cannot run a separate ground wire to the box.
J. V. is offline   Reply With Quote
Old 11-01-2009, 06:42 PM   #7
Member
 
CaptChaos's Avatar
 
Join Date: Aug 2009
Location: Weehawken, NJ
Posts: 58
Rewards Points: 75
Default

Grounding to Metal Box


Quote:
Originally Posted by AllanJ View Post
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?
CaptChaos is offline   Reply With Quote
Old 11-01-2009, 09:25 PM   #8
Member
 
Join Date: May 2009
Location: Brooklyn, New York (NYC)
Posts: 1,124
Rewards Points: 500
Thumbs up

Grounding to Metal Box


Quote:
Originally Posted by CaptChaos View Post
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)Don't Drink and Drive, Ever!!!
spark plug is offline   Reply With Quote
Old 11-02-2009, 09:08 AM   #9
Member
 
Join Date: Sep 2008
Location: Oregon
Posts: 1,497
Rewards Points: 500
Default

Grounding to Metal Box


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).
Billy_Bob is offline   Reply With Quote
Old 11-02-2009, 11:25 AM   #10
Member
 
Join Date: May 2009
Location: Brooklyn, New York (NYC)
Posts: 1,124
Rewards Points: 500
Thumbs up

Grounding to Metal Box


Quote:
Originally Posted by Billy_Bob View Post
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)Don't Drink and Drive, Ever!!!
spark plug is offline   Reply With Quote
Old 11-02-2009, 01:47 PM   #11
Member
 
WaldenL's Avatar
 
Join Date: Jan 2009
Location: Nassau, Long Island, NY
Posts: 349
Rewards Points: 268
Default

Grounding to Metal Box


Quote:
Originally Posted by spark plug View Post
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'.
WaldenL is offline   Reply With Quote
Old 11-02-2009, 07:48 PM   #12
Member
 
Join Date: May 2009
Location: Brooklyn, New York (NYC)
Posts: 1,124
Rewards Points: 500
Thumbs up

Grounding to Metal Box


Quote:
Originally Posted by WaldenL View Post
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 Through Education; (No matter what) Don't drink and Drive, Ever!!!

Advertisement

spark plug is offline   Reply With Quote
Reply

Tags
grounding. electrical , old house


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wire size for 300watt trans, 3 way 100ft Al the Diy guy Electrical 16 03-22-2008 09:46 PM
Grounding a non-grounded metal blower o2barockstar Electrical 1 10-22-2007 09:53 PM
grounding pole building sheet metal? borderbuster Electrical 2 07-08-2007 03:11 AM
NEC Question Jafsvcs Electrical 1 06-13-2007 06:45 PM




Top of Page | View New Posts