Raceway as the grounding conductor

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tommy

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Art 250.118 types of grounding conductors and I see EMT as that but for some odd reason we seem to shy away from using the conduit as grounding. If I recall it was common but now wire runs have the grounding conductor run inside with the other wires so basically 2 paths of ground. Any other sections for me to look at as to why. Maybe just something I noticed and never followed thru in checking.
 
tommy said:
Art 250.118 types of grounding conductors and I see EMT as that but for some odd reason we seem to shy away from using the conduit as grounding. If I recall it was common but now wire runs have the grounding conductor run inside with the other wires so basically 2 paths of ground. Any other sections for me to look at as to why. Maybe just something I noticed and never followed thru in checking.
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I am not sure of the specifics as to when or why electricians, designers, and engineers started shying away from using an approved raceway as the EGC. Its a complete waste of resources and money to pull a wire EGC. I hardly ever pull a wire EGC in EMT, whether it be 1/2" or 4". An exception would be in Washington where we are required to pull a wire EGC in wet locations.
 
Nothing else to check. As noted, 250.118 accepts EMT as an equipment grounding conductor. Much discussion has ensured as to the advisability of adding a wire type conductor but in the end it is simply a matter of personal preference.
 
I don't pull a green in emt or grc unless I'm told to. The conduit is a better equipment grounding conductor than any wire you could stuff in it. Job specs often will ask for a wire egc so sometimes there is no choice. The cult of the green wire is gaining strength in most parts of the country and it takes an electrician of strong character and conviction to resist.
 
I work in tons of old buildings as that's primarily what we have in my area, and it used to be standard practice to use the raceways as the EGC. Certainly anything wired in the 60's, 70's and well into the 80's almost never incorporated a wire EGC. I'm not sure why the practice began but if it's about compensating for bad workmanship, that is a sad indictment on the trade.
 
peter d said:
I work in tons of old buildings as that's primarily what we have in my area, and it used to be standard practice to use the raceways as the EGC. Certainly anything wired in the 60's, 70's and well into the 80's almost never incorporated a wire EGC. I'm not sure why the practice began but if it's about compensating for bad workmanship, that is a sad indictment on the trade.
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I don't have a problem with the install for the most part but EMT just does not hold up well over time. IMO, too flimsy to be used as an EGC except in an area with very limited access to the general public/employee.

I would and do use rigid for an EGC.
 
tommy said:
That is what I was thinking for here is better to install a conductor then assume conduit conductivity I guess
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Assume? ? Ohm it out.

Really. Put a multimeter on the neutral and the steel, out in a box on the EMT run. Keep a note pad in your pocket, or a file in your phone, and record conduit type / size / approx. length of run, neutral gage, and the resistance measured in Ohms. Do this on runs without a wire type EGC. In a second grouping, do the same with EMT runs WITH a wire type EGC.

Compare, share, discuss.
 
al hildenbrand said:
Assume? ? Ohm it out.

Really. Put a multimeter on the neutral and the steel, out in a box on the EMT run. Keep a note pad in your pocket, or a file in your phone, and record conduit type / size / approx. length of run, neutral gage, and the resistance measured in Ohms. Do this on runs without a wire type EGC. In a second grouping, do the same with EMT runs WITH a wire type EGC.

Compare, share, discuss.
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What good would that do? The resistance measured with an ohmmeter doesn't accurately reflect the conductivity of the conduit under load. The resistance of a 1 foot piece of #26 gauge copper wire is insignificant. How long will it carry the short circuit current of a 20 amp circuit?
 
As a commercial/light industrial service electrician, I've seen many emt conduits damaged/seperated by forklifts, etc. with the conductors still intact and operating. No equipment grounding at this point. Convinced me early on that installing an EGC in emt was a good idea. And, I often used it as pull wire when adding circuits at repeat customers.
 
Jim1959 said:
As a commercial/light industrial service electrician, I've seen many emt conduits damaged/seperated by forklifts, etc.
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In that case the EMT was not the right material for the job, see 358.12(1)

Roger
 
Strathead said:
What good would that do? The resistance measured with an ohmmeter doesn't accurately reflect the conductivity of the conduit under load. The resistance of a 1 foot piece of #26 gauge copper wire is insignificant. How long will it carry the short circuit current of a 20 amp circuit?
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Huh? :happysad: "Conductivity of the conduit under load"? The EMT does not conduct under load. What does a 26 AWG wire have to do with anything? Can you give a comparison of copper wire and EMT conductivity in the real world?
 
I agree that installing the green conductor may not be necessary. But, as mentioned earlier the damaged/separated conduit will eliminate the EGC. For the most part I install the EGC.
 
Jim1959 said:
As a commercial/light industrial service electrician, I've seen many emt conduits damaged/seperated by forklifts, etc. with the conductors still intact and operating. No equipment grounding at this point. Convinced me early on that installing an EGC in emt was a good idea. And, I often used it as pull wire when adding circuits at repeat customers.
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So basically you are saying by pulling an EGC you don't have to repair damaged conduits.

Like Roger I am of the belief that if you think the EMT is going to be damaged it is either not the right product or not being installed properly.
 
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dkidd said:
Huh? :happysad: "Conductivity of the conduit under load"? The EMT does not conduct under load. What does a 26 AWG wire have to do with anything? Can you give a comparison of copper wire and EMT conductivity in the real world?
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The point is, the milliamps conductivity behavior that you'd measure with an ohm-meter can be different than the kiloamps conductivity behavior that the circuit might actually have to endure during a fault.
 
It's already been proven that EMT is a better fault clearing path than a wire EGC by the industry itself with official tests, no need to do your own studies.
 
iwire said:
So basically you are saying by pulling an EGC you don't have to repair damaged conduits.

Like Roger I am of the belief that if you think the EMT is going to be damaged it is either not the right product or not being installed properly.
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I'm not referring to conduits I installed, just those I've witnessed. But I agree with your assessment.
 
dkidd said:
Huh? :happysad: "Conductivity of the conduit under load"? The EMT does not conduct under load. What does a 26 AWG wire have to do with anything? Can you give a comparison of copper wire and EMT conductivity in the real world?
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Read the statement and my response. My point was that an ohmmeter, does not take in to account the current carrying capacity of a conductor. So, using a multimeter to prove that an EMT conduit run is properly assembled and will act as a proper ground path is not effective. Every coupling and connector could be loose, and you could still be capable of reading virtually zero ohms.
 
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