Wire type EGC in the NEC

mbrooke

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A GFCI will also clear a ground fault an EGC won't. For instance, suppose someone touched a hot wire and a small amount of current went through his/her body to ground. The small amount of current would not open the OCPD but the GFCI should sense it and clear the fault.

Also a GFCI will not clear a hot to neutral fault at all.

So really for best protection you need both where the risk warrants it.


Correct, under direct contact conditions only a GFCI will save you.

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DrSparks

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Madison, WI, USA
A person has to get shocked first, (touch the faulted object) before a GFCI will open.

Where an EGC will remove voltage from the surface of an object regardless.
Yes this it true but GFCIs still save lives. Remember one of the major factors of shock severity and mortality is duration.

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DrSparks

Senior Member
Location
Madison, WI, USA
A GFCI will also clear a ground fault an EGC won't. For instance, suppose someone touched a hot wire and a small amount of current went through his/her body to ground. The small amount of current would not open the OCPD but the GFCI should sense it and clear the fault.

Also a GFCI will not clear a hot to neutral fault at all.

So really for best protection you need both where the risk warrants it.
A hot to neutral fault... you mean a load?



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mbrooke

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Yes this it true but GFCIs still save lives. Remember one of the major factors of shock severity and mortality is duration.

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Of course!

However, how many do the right thing and consider breaker opening time when sizing a circuit?
 
Yeah I look at it as an insurance policy. I see EMT popped out of couplings everywhere I go.

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So if the workmanship is so atrocious that the EMT is just falling apart everywhere, what makes you so confident that the workmanship on the green wire connections won't be equally as atrocious? Or for that matter any number of other things not even related to an effective ground fall current path?
 

roger

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Yeah I look at it as an insurance policy. I see EMT popped out of couplings everywhere I go.

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And in a building with metal framing, metal plumbing, sprinklers, HAVC ducts, steam lines, etc.... the conduit would still be the better fault clearing path.

Roger
 

mbrooke

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And in a building with metal framing, metal plumbing, sprinklers, HAVC ducts, steam lines, etc.... the conduit would still be the better fault clearing path.

Roger

That is until you get robot construction with plastic, epoxy, carbon or concrete construction. PEX pipe, CST gas, fiber optics.
 
Rarely used ≠ correct or code complaint.

How many run the equation here?

View attachment 2557159
If you run the numbers, you will see it is not an issue. Plus note the code does not specify a maximum length change that triggers use of expansion joints for steel conduit.

How much experience do you have working with EMT and around existing EMT installations? Do you have a good depth of experience that confirms all these problems you purport of joints loosening and corrosion at joints? Are you even an electrician?
 

mbrooke

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If you run the numbers, you will see it is not an issue. Plus note the code does not specify a maximum length change that triggers use of expansion joints for steel conduit.

How much experience do you have working with EMT and around existing EMT installations? Do you have a good depth of experience that confirms all these problems you purport of joints loosening and corrosion at joints? Are you even an electrician?

What are you basing the number on? If you assume every part of the building stays at 72*F all year round then maybe.
 

Fred B

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Upstate, NY
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Electrician
Most EMT interior of building will not normally see the range of temperature to require expansion coupling, exterior roof top might see enough variation. That said interesting that the code directly addresses expansion in PVC and RTRC, but omits any mention in relationship to EMT, RMC, or IMC.
Using the section quoted and assuming a .25 expansion limit similar to PVC, if using steel EMT to reach the max expansion to require special joint would require more than 80 ft @40°F temp variation. A temperature change typical on exterior rooftop might see of 120°F would require it at 30ft. In order to require expansion joint on a ten ft piece between connection it would require a temperature change of 320°F, even a roof top would be hard pressed to get that. And then what derating of conductor would be required under that circumstance. All this is assuming a .25 expansion limit.
I agree with @electrofelon that practicality says that EMT not likely to ever require expansion joint inside.
 
Most EMT interior of building will not normally see the range of temperature to require expansion coupling, exterior roof top might see enough variation. That said interesting that the code directly addresses expansion in PVC and RTRC, but omits any mention in relationship to EMT, RMC, or IMC.
Using the section quoted and assuming a .25 expansion limit similar to PVC, if using steel EMT to reach the max expansion to require special joint would require more than 80 ft @40°F temp variation. A temperature change typical on exterior rooftop might see of 120°F would require it at 30ft. In order to require expansion joint on a ten ft piece between connection it would require a temperature change of 320°F, even a roof top would be hard pressed to get that. And then what derating of conductor would be required under that circumstance. All this is assuming a .25 expansion limit.
I agree with @electrofelon that practicality says that EMT not likely to ever require expansion joint inside.
And on roofs, typically the conduit is floating on dura blocks so I don't see what need there is for an expansion joint, unless you have a straight run between two pieces of equipment
 

mbrooke

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Technician
Most EMT interior of building will not normally see the range of temperature to require expansion coupling, exterior roof top might see enough variation. That said interesting that the code directly addresses expansion in PVC and RTRC, but omits any mention in relationship to EMT, RMC, or IMC.
Using the section quoted and assuming a .25 expansion limit similar to PVC, if using steel EMT to reach the max expansion to require special joint would require more than 80 ft @40°F temp variation. A temperature change typical on exterior rooftop might see of 120°F would require it at 30ft. In order to require expansion joint on a ten ft piece between connection it would require a temperature change of 320°F, even a roof top would be hard pressed to get that. And then what derating of conductor would be required under that circumstance. All this is assuming a .25 expansion limit.
I agree with @electrofelon that practicality says that EMT not likely to ever require expansion joint inside.


It is a misconception that expansion joints are required only for PVC.

https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=275.0
 
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