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#164686 - 06/08/07 05:59 PM Grounding & Bonding
Rab Offline
Member

Registered: 05/23/07
Posts: 11
Loc: Canada
Hello all i have a some questions regarding the ontario elect. code on grounding and bonding.It seems today at work the topic understanding the interpretation of the code and how it would apply to the electrical done in the past and passed inspection. We all can read the code book but it seems their is many interpretations of grounding and bonding and it makes it confusing.Scenario:lets say the main panel is grounded and we decide to run a number of circuits using emt conduit to various locations in a plant, we follow the code by adding pull boxes were needed and we install disconnects for motors.We pull our circuits in the emt with a ground and terminate the ground in the disconnects and motors. Is this sufficient for grounding and bonding? and does the emt act as a bond between all non electrical equipment?
To me this is not correct, i read it as the disconnects and outside casing of the motors must be bonded independantly from the ground that was pulled with circuits. I notice in the plant that many disconnects and motors do not seem to be bonded as per the code.
Any thoughts, opinions, answers, would be great.
thanks Rab

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#164698 - 06/08/07 07:20 PM Re: Grounding & Bonding [Re: Rab]
RobbieD Offline
Member

Registered: 02/23/03
Posts: 238
Loc: Canada
If your main CDP is grounded then anything that you attach to the ground bus going out to the circuits is bonding. When you have a green going to your disconnect and motor this is a bonding wire.
You don't have to use a bonding conductor in emt. the emt can act as the bond as long as is complies to 10-804. Most places want the bond in the emt as well. This is good practice just incase something comes apart. You run a bonding conductor in your flex going to your motor as well.

Just look at the definitions of grounding and bonding again.

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#164703 - 06/08/07 10:40 PM Re: Grounding & Bonding [Re: RobbieD]
Rab Offline
Member

Registered: 05/23/07
Posts: 11
Loc: Canada
RobbieD thanks for the response. This is the definition of Bonding: a low impedance path obtained by permantely joining all non current carrying metal parts to assure electrical continuity and having the capacity to conduct safely any current likely to impose on it. This definition emphasizes the permanence of the connection, positive continuity, ampacity to conduct fault current and applies to electrical equipment being connected so that no potential exists between the equipment and earth (induced voltage). Grounding: is a permanent and continous grounded path to earth with a low impedance and can carry the ampacity at all times to prevent any current to be imposed on the grounding conductor and from causing a harmful voltage to exsist between it and earth.I dont have my code book in front of me so i am going with what i remember the issue we are having is grounding and bonding are two different things and usually equipment or non current carrying equipment should be bonded in which you can use the building steel structure to do so, bringing in a ground wire from the main panel is not bonding as your emt is being used to carry current circuits and the emt could potentially be seperated at a point creating the continuity to be broken.

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#164754 - 06/10/07 04:15 PM Re: Grounding & Bonding [Re: Rab]
RobbieD Offline
Member

Registered: 02/23/03
Posts: 238
Loc: Canada
 Quote:
bringing in a ground wire from the main panel is not bonding as your emt is being used to carry current circuits and the emt could potentially be seperated at a point creating the continuity to be broken.


Unless that green wire that you bring from the CDP in the emt with all your cicuit conductors is going directly to the grounding electrode without any joints, it is a bonding conductor.


Maybe I just don't understand what you want to know. If you have cicuits in emt and you decide to run a bond conductor in the pipe. Then you have the emt bonded by means of the emt and it is also bonded by the bonding conductor inside it. As long as you properly terminate the bonding conductor at all the boxes and equipment it means for a really good bond to ground. The wire inside is good practice for conditions just like you said about the emt coming apart.

I would say that it would be best to forget about the word ground unless you are at the service or transformers or a couple of other instances. Everything past the service is BONDING.

Maybe just give an example with yes or no type answer that you have.

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#164983 - 06/15/07 05:33 PM Re: Grounding & Bonding [Re: RobbieD]
Rab Offline
Member

Registered: 05/23/07
Posts: 11
Loc: Canada
Okay this is what i have at the moment. Their is a 120/208 volt main circuit panel which is grounded, from the panel their is a 1 1/4" EMT conduit running to a 6"x6" JB/PB, in this 1 1/4" Emt their is 10 circuit wires and 1 neutral wire (All this was existing) from this point i installed 1/2" Emt to a JB on the wire carousel (the carousel is an all solid steel structure with 2 - 1H.P motors they are feed with armour cable in the framing of the carousel. From the JB their is another armoured cable feeding the controls). In the 1/2" Emt with 3 wires as the carousel requires 3 phase 208v and draws 7.6 amps. No green wire was pulled in any of the emt piping fronm the main panel, the armoured cable has a green wire and is terminated under the ground screw of the JB and motor enclosure. I ran a #6 bare ground from the the carousel framing to the building steel frame structure for a bond in which i was told by the esa inspector that it was not required as the emt was sufficient for the bonding of all. To me and the way i read the code book a ground wire should be run all the way back to th emain panel to act as a ground for the motors and controls but obvoiusly i am interpertating this all wrong. I have read the code book section on grounding and bonding and i see it as any non electrical steel equipment should be bonded to a seperate grounded part of the ground system which should be the building structure ground and that the electrical equipment shall be grounded with a seperate ground back to the panel. I guess i have gotten my self really confused with this section of the code. is their any easier way to understand this section?

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#165155 - 06/20/07 04:53 PM Re: Grounding & Bonding [Re: Rab]
RobbieD Offline
Member

Registered: 02/23/03
Posts: 238
Loc: Canada
Yes, I think that there is.

When I was first starting to look at the code I used the CEC because I was in a different province. I found it real helpful to have a copy of the CEC Simplified (Illustrated) Code Book for reference. I know that you are using the OESC but it is very similar to the CEC. Maybe the OESC has one similar. There are also other illustrated books out there, I think that Knight has one, that one is good also because he gives real life examples in it. If I were you I would get a hold of any of these books (perfer the CEC). I still learn things everyday but alongtime ago these books helped me understand things better. That and asking other people with lots of experience, don't take everything that people say as being true, I would always cross reference it to the code book just to make sure.


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#165394 - 06/26/07 07:15 PM Re: Grounding & Bonding [Re: RobbieD]
mr_electrician Offline
Member

Registered: 06/22/07
Posts: 106
Loc: London, Ontario
My code teacher always drilled into our heads that grounding is only done at the service, everything else is a bond.
_________________________
Never trust an electrician with no eyebrows!!

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#165395 - 06/26/07 07:16 PM Re: Grounding & Bonding [Re: mr_electrician]
mr_electrician Offline
Member

Registered: 06/22/07
Posts: 106
Loc: London, Ontario
Greater is he who is in me, then he who is in the world!
_________________________
Never trust an electrician with no eyebrows!!

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#165720 - 07/04/07 04:30 AM Re: Grounding & Bonding [Re: mr_electrician]
Navyguy Offline
Member

Registered: 10/14/05
Posts: 29
Loc: Welland, Ontario, Canada
Perhaps it may be easier to think or remember that you do not want two sources to ground for any one system. Think of your standard dist system, there is only one ground (at the plate/rod or water main) everything else ties back to the panel…therefore they are bonded to ground.

Just use this basic explanation and apply that to more complicated systems. When you start talking about “isolated grounds” which really should be called “isolated bonds”, you are isolating them from other metal parts that are also bonded and you are connecting it directly to the grounding system. In this case, you are not duplicating the ground but are bringing a bonding wire directly back to the ground system.

Hope this helps.

Cheers

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#168728 - 09/13/07 10:12 AM Re: Grounding & Bonding [Re: Navyguy]
Rab Offline
Member

Registered: 05/23/07
Posts: 11
Loc: Canada
Sorry everyone who responded to my question, i have been away for awhile and just getting back. Thank you to all who responded, i think i am now less confused and understand it but i know down the road something else will come up and it will confuse the issue again, someone will always have questions with grounding and bonding.
Thanks Rab

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