Where in the code...

[outpace]

I have NEC 2008 on CD and have been searching to find where it may clearly (?!) state the rules for the following:

1. When an insulated bonding ('ground') conductor is run through EMT, on its own, that the EMT must be bonded to ground (e.g. via bushings at both ends, to either the 'ground' that is running through it or to a separately sourced 'equipment' ground - that is, a typical electrical ground as opposed to potentially tainting the 'isolated ground' which is running through the EMT).

2. That EMT may be used on a rooftop installatoin, e.g. power running across a rooftop (on supports of some sort) to an equipment cabinet. 'Standard' EMT I gather has a protective coating of sorts (light galvainzing for example). I also think that 'compression' (somewhatever watertight) fittings must be used... An engineer (eek!) stated that only RIGID metal conduit may be used on a rooftop - all electricians I talk to disagree. (Let's leave Sched 80 PVC out of htis discussion.)

Tnx!

 

[Dennis Alwon]

I don't understand #1. Art. 358.60 allows emt to be used as an equipment ground. Adding an insulated egc does not change the fact that the emt must be continuous. 250.120(A)

 

[raider1]

I have NEC 2008 on CD and have been searching to find where it may clearly (?!) state the rules for the following:

1. When an insulated bonding ('ground') conductor is run through EMT, on its own, that the EMT must be bonded to ground (e.g. via bushings at both ends, to either the 'ground' that is running through it or to a separately sourced 'equipment' ground - that is, a typical electrical ground as opposed to potentially tainting the 'isolated ground' which is running through the EMT).

If you are talking about a grounding electrode conductor take a look at 250.64(E)

2. That EMT may be used on a rooftop installatoin, e.g. power running across a rooftop (on supports of some sort) to an equipment cabinet. 'Standard' EMT I gather has a protective coating of sorts (light galvainzing for example). I also think that 'compression' (somewhatever watertight) fittings must be used... An engineer (eek!) stated that only RIGID metal conduit may be used on a rooftop - all electricians I talk to disagree. (Let's leave Sched 80 PVC out of htis discussion.)

Tnx!

Take a look at 358.10 (A), (B) and (C) for uses permitted for EMT.

Chris

 

[raider1]

I don't understand #1. Art. 358.60 allows emt to be used as an equipment ground. Adding an insulated egc does not change the fact that the emt must be continuous. 250.120(A)

I am wondering if he is asking about a GEC.

Chris

 

[outpace]

250.64(E) does answer question 1 - thanks.

But I am still not clear on the EMT usage outdoors. The code references (which I had read before) indicate that it is fine to use indoors and outdoors, and, if outdoors, there must be corrosion protection. So, does 'standard' EMT come with such a corrosion-resistant coating (e.g. light galvanizing, or ???)... I was also told that 'compression' fittings must be used outdoors as they are somewhat watertight... darn code simply does not 'read' clearly enough for me. sigh.

 

[macmikeman]

Bonding both ends of a ferrous metal conduit, box, or raceway, is required when the conductor inside is the grounding electrode. * (could be also bonding jumpers at the service as well). Thats the only time its required. See 250.64 (E)

Emt on a roof is acceptable to the NEC provided "raintight" couplings and connectors are used if that roof is a wet location.

 

[Dennis Alwon]

Corrosion protection is required when EMT is used underground.

 

[raider1]

I agree with Dennis and Mike,

EMT run on a roof does not required additional corrosion protection. Raintight fittings are required for EMT run in a wet location. Standard compression fittings are no longer listed as raintight, you must make sure that the compression fittings that you are going to use are currently listed as raintight.

Chris

 

[cowboyjwc]

I too don't understand the first question. Unless he's talking about 250.64(E).

As for the second, many engineers and even many jurisdictions do not allow EMT on the roof as they tend to get knocked apart or bent when stepped on so they require rigid. Some engineers also spec that no conduit is to be run on the roof and must be run below the roof.

 

[raider1]

I too don't understand the first question.

The OPer is asking about 250.64(E) for a GEC.

As for the second, many engineers and even many jurisdictions do not allow EMT on the roof as they tend to get knocked apart or bent when stepped on so they require rigid. Some engineers also spec that no conduit is to be run on the roof and must be run below the roof.

Agreed, I have seen engineers specifications that required the use of ridged metal conduit on a rooftop.

Chris

 

[cowboyjwc]

The OPer is asking about 250.64(E) for a GEC.




Chris

Yeah, took me a minute to think about it and look it up. As you can see I've edited my answer, just before I saw yours.

 

[Chev]

For your EMT grounding question, I believe 250.92(A)(3) would apply. As to the EMT v/s Rigid argument, is the engineer the AHJ for the project? If so, he gets what he wants due to the industrial "God clause" as I call it. It depends on the exposure to damage of the EMT, but if it is a plant setting without electrical inspection, the engineer wins and gets what he wants despite "popular opinion".