Posted: 3/1/2017 9:47:35 PM EDT
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I have a metal outlet box in my garage. I've noticed that there are only two (hot/neutral) coming through the EMT. The outlet is then grounded to the back of the metal box via single green wire and green screw. There are no other ground wires entering or leaving the box. Is this okay??
Photo to demonstrate: 
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Quoted:
I have a metal outlet box in my garage. I've noticed that there are only two (hot/neutral) coming through the EMT. The outlet is then grounded to the back of the metal box via single green wire and green screw. There are no other ground wires entering or leaving the box. Is this okay?? Photo to demonstrate: http://pad3.whstatic.com/images/thumb/8/8b/Ground-an-Outlet-Step-8-Version-2.jpg/aid1353565-728px-Ground-an-Outlet-Step-8-Version-2.jpg if it is truly EMT (Electrical metallic tubing), and it is properly grounded, that setup is code compliant. the jpeg you included, however, shows flexible metallic conduit -- which could go a couple of ways... ar-jedi |
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Quoted:
the metallic jacket of old style BX (aka "Greenfield") can not be used as the EGC ("ground"). modern "AC" (armored cable) has an internal aluminum strip which serves as the EGC. ar-jedi http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/images/111ecmCBfig1.jpg Quoted:
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is the wiring a BX type or metal shielded? if so, then that's fine. the metallic jacket of old style BX (aka "Greenfield") can not be used as the EGC ("ground"). modern "AC" (armored cable) has an internal aluminum strip which serves as the EGC. ar-jedi http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/images/111ecmCBfig1.jpg Thx for the extra clarification |
| While the EMT can be used as a ground, if you want to go one step above you should run a ground wire. A loose connection on the EMT could interrupt the ground and as unlikely that is, it's still a risk. I'm working on wiring a garage right now and I plan to run a separate ground wire inside the EMT just to be sure. 10 ga (good for up to 50 amp circuits for the ground) isn't that expensive to run. |
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Quoted:
While the EMT can be used as a ground, if you want to go one step above you should run a ground wire. A loose connection on the EMT could interrupt the ground and as unlikely that is, it's still a risk. I'm working on wiring a garage right now and I plan to run a separate ground wire inside the EMT just to be sure. 10 ga (good for up to 50 amp circuits for the ground) isn't that expensive to run. If you use set screw type EMT connectors it makes a lousy ground long term. If you use compression style and toque them up solidly it lasts a long time if you pay attention to material compatibility. Galv steel for everything is better than mixing in other metals. We had to use compression connectors on EMT for classified network protection and shielding. The tiny contact area of the set screw style made the signal leakage horrid. It was a good thing we ran some actual tests before installing a system that would have failed when finished and checked then. |