Forums | Home Repair | Home Improvement | Painting | Interior Decorating | Remodeling | Landscaping


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

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

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-16-2013, 08:34 AM   #1
Member
 
Join Date: Mar 2013
Location: Chicago suburbs
Posts: 214
Share |
Default

Grounding pigtails


Had a thought while reading another post...

Why is it that when you use NM cable with metal boxes, you need to pigtail the grounds to the box and to the device... but when using conduit, the device does not need to be grounded to the box other than via the screws?

If the screws on the device are good enough to make the ground connection in a conduit setup, why are they not sufficient in an NM setup?
SquishyBall is offline   Reply With Quote
Old 04-16-2013, 09:02 AM   #2
Member
 
Join Date: Feb 2013
Location: West Virginia
Posts: 127
Default

Grounding pigtails


Conduit is considered the ground path (unbroken metal clear from box to panel). With NM, that metallic path is not there, so it uses the ground wire as the path.
al_smelter is offline   Reply With Quote
Old 04-16-2013, 09:14 AM   #3
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,062
Default

Grounding pigtails


From 2011 NEC 406.4(C) Methods of Grounding.
The equipment grounding conductor
contacts of receptacles and cord connectors shall be
grounded by connection to the equipment grounding conductor
of the circuit supplying the receptacle or cord connector.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
Old 04-16-2013, 11:13 AM   #4
Member
 
Join Date: Mar 2013
Location: Chicago suburbs
Posts: 214
Default

Grounding pigtails


Quote:
Originally Posted by al_smelter View Post
Conduit is considered the ground path (unbroken metal clear from box to panel). With NM, that metallic path is not there, so it uses the ground wire as the path.
Of course. But that's not the question.

So with NM, and say two wires in and out. ground 1 and ground 2 are joined with two pigtails - one to the metal box and one to the device.

With conduit, the metal raceway is the ground, fine. Yet you do not need to ground your device. The connection via the screws is sufficient.

Why is that screws connection not sufficient with NM with a grounded metal box?

Quote:
Originally Posted by al_smelter View Post
contacts of receptacles and cord connectors shall be grounded by connection to the equipment grounding conductor
But with conduit it's ok to just use the screws for that. Why are the screws less effective w NM in a metal box. The metal box is just as grounded (from the pigtail) as it is w conduit (from the metal raceway).
SquishyBall is offline   Reply With Quote
Old 04-16-2013, 11:54 AM   #5
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,447
Default

Grounding pigtails


I don't get it either, and have often wondered about this. It seems to me that a grounding connection should only be required in one location at each box. Bond the box, and the devices should be effectively bonded too. Bond a device, and the box should be effectively bonded too (and probably any other devices in that box). Pigtailing everything seems totally redundant. I would understand it if the device-to-box connection were never considered acceptable for bonding. But it is allowed if the box is grounded through conduit, so the box-to-device connection has been tested and found adequate under those circumstances. Why is that a special case? Why isn't that connection always considered good enough? I don't ever expect answers to these questions. The NFPA often seems like a phony psychic, handing out dubious advice with no explanation.
__________________
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
mpoulton is offline   Reply With Quote
The Following User Says Thank You to mpoulton For This Useful Post:
junkcollector (04-18-2013)
Old 04-18-2013, 09:38 AM   #6
Member
 
Dana56's Avatar
 
Join Date: Mar 2013
Posts: 76
Default

Grounding pigtails


Always pigtail grounds to box and device no matter what it dont take much and its good practice. Dont think anybody relies on conduit as ground anymore, u always pull a ground in pipe
Dana56 is offline   Reply With Quote
Old 04-18-2013, 04:17 PM   #7
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,245
Default

Grounding pigtails


Quote:
Originally Posted by SquishyBall View Post
Had a thought while reading another post...

Why is it that when you use NM cable with metal boxes, you need to pigtail the grounds to the box and to the device...


What makes you think you have to?
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
stickboy1375 is offline   Reply With Quote
Old 04-18-2013, 04:22 PM   #8
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,245
Default

Grounding pigtails


Quote:
Originally Posted by Dana56 View Post
Always pigtail grounds to box and device no matter what it dont take much and its good practice. Dont think anybody relies on conduit as ground anymore, u always pull a ground in pipe
Thats a nice opinion you have....but not required.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
stickboy1375 is offline   Reply With Quote
Old 04-18-2013, 04:26 PM   #9
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,245
Default

Grounding pigtails


Quote:
Originally Posted by mpoulton View Post
I don't get it either, and have often wondered about this. It seems to me that a grounding connection should only be required in one location at each box.
And in some cases that's all you are required.


Quote:
Originally Posted by mpoulton View Post
Bond the box, and the devices should be effectively bonded too.
This is true if you are using self grounding receptacles, switches are allowed to be bonded with the 6-32 alone....


Quote:
Originally Posted by mpoulton View Post
Bond a device, and the box should be effectively bonded too (and probably any other devices in that box).
You cannot have the device solely bond the box, think about it, what if the device is removed?
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
stickboy1375 is offline   Reply With Quote
Old 04-18-2013, 04:33 PM   #10
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,245
Default

Grounding pigtails








I know the pictures show EMT as the wiring method, but any wiring method can be applied to this.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
stickboy1375 is offline   Reply With Quote
Old 04-18-2013, 05:30 PM   #11
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,447
Default

Grounding pigtails


Quote:
Originally Posted by stickboy1375 View Post
You cannot have the device solely bond the box, think about it, what if the device is removed?
That is a good point. I suppose the code writers are concerned that someone would remove the device that is bonding the box, and replace it incorrectly.
__________________
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
mpoulton is offline   Reply With Quote
Old 04-18-2013, 08:02 PM   #12
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,062
Default

Grounding pigtails


Quote:
Originally Posted by stickboy1375 View Post






I know the pictures show EMT as the wiring method, but any wiring method can be applied to this.
Note that only applies to surface mounted boxes and certain covers. Flush mount needs both to be bonded together.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
The Following User Says Thank You to Jim Port For This Useful Post:
k_buz (04-18-2013)
Old 04-18-2013, 09:03 PM   #13
Member
 
Dana56's Avatar
 
Join Date: Mar 2013
Posts: 76
Default

Grounding pigtails


Quote:
Originally Posted by stickboy1375

Thats a nice opinion you have....but not required.
Glad u like it... Like to go a little more than "minimum requirement" never know if set screws are properly tightened to ensure good ground thanks for input
Dana56 is offline   Reply With Quote
Old 04-18-2013, 09:35 PM   #14
Licensed Electrician
 
k_buz's Avatar
 
Join Date: Mar 2012
Location: SE Wisconsin
Posts: 4,221
Default

Grounding pigtails


Quote:
Originally Posted by Jim Port View Post
Note that only applies to surface mounted boxes and certain covers. Flush mount needs both to be bonded together.
This is true, however, they do make listed self-grounding receptacles that would not need a ground run to it.
__________________
__________________________________________________ ______________
Answers based on the National Electric Code. Always check local amendments.


k_buz is online now   Reply With Quote
The Following User Says Thank You to k_buz For This Useful Post:
stickboy1375 (04-19-2013)
Old 04-18-2013, 10:19 PM   #15
Member
 
Dana56's Avatar
 
Join Date: Mar 2013
Posts: 76
Default

Grounding pigtails


Bonding bushings or locknuts mite be required too if the box has concentric knockouts just another nice opinion )
Dana56 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
2-2-4 SEU - Smaller Neutral? BRT Electrical 18 09-23-2012 09:25 PM
Replacing Light Fixture with No Ground Wire in Home panorama Electrical 42 09-14-2012 09:35 AM
Bare grounding pigtails? smata67 Electrical 2 05-27-2012 07:27 AM
Need to know if my grounds and neutrals are connected right dorlow Electrical 185 01-15-2012 02:54 PM
NEC Question Jafsvcs Electrical 1 06-13-2007 05:45 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.