Grounding wire for pole lights

[james wuebker]

Have outside pole lights(277v). All outside is ran it pvc that then comes into building to a 6x6 j-box. From the lights outside 1 hot, 1 neutral & 1 grounding wire. Now the feed for the lights are fed from a 20 amp breaker to the j-box. The feed has only a neutral and a hot wire and they are using the emt conduit for a grounding wire. The grounding wire from the lights are only bonded to the j-box. I believe this is code but where in the book do I find this. I don't like this method because you never know that if someone hits the conduit then it breaks away then you are without a ground. What do you think about this.
Jim

 

[tom baker]

Re: Grounding wire for pole lights

EMT is allowed as a equipment grounding conductor or path, see 250.118. As the PVC has an equipment grounding conductor (wire) then it also complies with 250.118. Your objective is to create an effective low impedance ground fault return path. per 250.4(A)(4)
Yes its true the EMT could be damaged, if you feel its unsafe then you can always pull an equipment grounding conductor. However if the EMT connections are tight, and as its 277V if there are reducing washers or concentric KO's it complies with Art 250,but take a look at 250.97 for circuits over 250V to ground.

 

[james wuebker]

Re: Grounding wire for pole lights

Thanks Tom.
Jim

 

[friebel]

Re: Grounding wire for pole lights

GROUND WIRE FOR POLE LIGHTS, To: James Wuebker,
I do agree with your assessment about just using the metal raceway for the sole equipment grounding conductor.
We did this for many years in the Industrial Plant where I worked. But, finally the Design Engineer in charge put out the edict that we would also carry an equipment grounding conductor in the raceway.
To my way of thinking, it just makes for a safer installation. I have seen when we just used the raceway as the EGC, and it was broken, then you would lose your ground. Another thought, I have experienced the couplings on the conduit becoming corroded and then you have lost your continuity of your ground.

 

[augie47]

Re: Grounding wire for pole lights

Show me any installation with 1000' of 1/2 or 3/4 EMT and I'll show you at least 1 fitting not made up well enough to provide low impedance ground.
If you want to assure its grounded, you best install a EGC.
(and 1000' is probably stretching it)

 

[petersonra]

Re: Grounding wire for pole lights

I question whether 1000' run of EMT is an adequate EGC in any case.

Will the impedance in such a length of small EMT trip an OCPD in the event of a ground fault that far away. it's not something I typically deal with a whole lot, but I read an interesting article a few years ago about this very issue.

a little googling found this:

http://www.electrician.com/electa1/ground2.html

[ August 19, 2005, 09:18 AM: Message edited by: petersonra ]

 

[don_resqcapt19]

Re: Grounding wire for pole lights

If you run the GEMI software for a 120 volt circuit with a 150 amp fault current, you will find that a #12 copper EGC is good for about 160' and 1/2" EMT for about 200'. Yes, this assumes that all of the EMT couplings and connectors are properly installed.
Don

 

[james wuebker]

Re: Grounding wire for pole lights

It looks like some of you would agree with we that you should run a grounding wire instead of using the conduit as a grounding method. There's been a lot of plants I've been in where I've seen conduit breaks. Most of them were going up the walls or lower areas. A lot of them looks like maybe a forklift hit them and of course the operators aren't going to say anything about it or maybe they didn't know they did it. I myself would feel better running a grounding wire and I believe they should take a closer look at this about changes in the code.
Thanks everyone,
Jim

 

[charlie]

Re: Grounding wire for pole lights

I believe they should take a closer look at this about changes in the code.

Jim, there is nothing wrong with a well maintained conduit system that is not subject to damage. The problem arises where conduit is used in areas where it is subject to damage (people running into it with equipment on factory floors, across roofs, etc.) Any time you feel that the grounding continuity is subject to interruption, it is your responsibility to install a grounding conductor with the circuit conductors. The bottom line is that this is a design issue and code making panel 5 is well aware of these problems. Beefing up the system past the minimum requirements has always been a design issue.

 

[augie47]

Re: Grounding wire for pole lights

The problem arises where conduit is used in areas where it is subject to damage

No doubt this is the primary problem, however, it has been my experience that often the problem in closly associated with the electricians tool pouch...there are few EMT jobs I see where at least some fittings aren't loose (that was my reference to the 1000' post..not one run,,just that quantity of pipe). I believe the only reason we don't see a bigger problem is multiple conduits and building steel providing alternate return paths. In my old age, I';m pessinistic, I don't expect to see a change, but in CMP 5 was as interested in this isuue as they are in some others, an EGC would be required with EMT.

No offense meant, charlie

 

[iwire]

Re: Grounding wire for pole lights

Originally posted by augie47:
I believe the only reason we don't see a bigger problem is multiple conduits and building steel providing alternate return paths.

I think you nailed two things on the head.

1)It works as it is, for whatever reasons

2)There is no 'big problem' to address.

What I mean by that is that the NEC generally does not fix what is not broke.

In order to get some interest in requiring copper EGCs you would have to show a definite problem.

Broken, damaged, or improperly installed raceways are not the kind of ammo that will do it.

You would need to show that a properly installed and undamaged raceway is not a suitable EGC.

As Don post shows many times a properly installed raceway has lower impedance than the copper conductor we would install in the raceway.

 

[friebel]

Re: Grounding wire for pole lights

I am replying to Charlie, Moderator.
Charlie, you mention that there is not a problem with a well maintained system for checking conduits for damage, etc.
Charlie, I do agree with you, BUT, I worked on a Chemical plant for 45 years, and back when I was an apprentice, one of my duties was to check all of the conduits, process piping, building steel, to make sure that they were all zero ohms to ground. We did this on a annual basis in a high-hazard, electrical classification area. In a non-hazardous area, we did it every three years.
When we would come to a conduit coupling that had lost it's conductivity due to corrosion, etc., we would install a jumper strap around the coupling.
Today, sad to say, the plant where I worked the workforce has been cut back so far that Preventative Maintenance is overlooked.

 

[james wuebker]

Re: Grounding wire for pole lights

Very good replies but if you didn't have to worry about the money or time installing a grounding wire instead of using the conduit for the ground which way do you really think is the best. I would feel safer if it had the ground wire in the run. All it takes is 1 no ground and it's going though you and a life may be lost. Maybe I'm just blowing out of my behind but safety is very important in my job. I like to see my family when I get home. I know the odds of getting shocked will be low but I still feel it should be ran.
Jim

 

[iwire]

Re: Grounding wire for pole lights

Hi Jim

Originally posted by james wuebker:
if you didn't have to worry about the money or time installing a grounding wire instead of using the conduit for the ground which way do you really think is the best.

Best IMO would be the use of both, as it provides redundancy.

Originally posted by james wuebker:
I would feel safer if it had the ground wire in the run. All it takes is 1 no ground and it's going though you and a life may be lost.

The same can be said when using a grounding wire in PVC conduit, or the grounding wire in NM.

All it takes is one bad connection and grounding continuity is lost.

Nothing wrong with wanting to go beyond the NEC.

That said I doubt we will see the NEC do away with the raceway grounding method.

 

[james wuebker]

Re: Grounding wire for pole lights

iwire
I agree.
Jim

 

[na112233]

Re: Grounding wire for pole lights

I recently read a new requirement for installing equipment ground in all rooftop raceways---if anyone knows where to find it I'd appreciate your input-may be in Oregon or Washington addendum to NEC. Anyway I believe it's a much better way to go with equip. grounding conductor in any outside conduit where the corrosion factor is higher and maintenance often neglected until something fails. I am glad to see the code leaning this way.