EMT as grounding

[Jim W in Tampa]

What EMT is as a ground is often 10 or more couplings with 2 screws each. That adds up and chances of 1 that got missed is higher. We do not always fasten to building steel. I have done a few parking garages and that can easily be up to 500 feet or more and that is 1,000 screws. Even the very best electricians can miss 1 when they run hundreds of feet a day. Yes if tight connections the steel is a very good ground. What we see in the field is often abuse to the systems from being damaged by other workers and users. Fork lifts can easily open up a section. No we cant make everything perfect.
If you were offered a system with the added ground or without and price was the same would you reject the ground wire ?

Kind of like buying tires for your car. Cheap ones are legal and reasonably safe but some select ones that cost far more. When your going 90 down the highway just remember what you selected.

Perhaps some here simply been working too long in a company that does as little as they must.

 

[Jim W in Tampa]

I agree 100%, I am just against a code change requiring the wire EGC.

That part I will agree with you on. Each condition is not the same.

 

[stevebea]

Try and follow along. :grin:

In a wood framed house with NM all it would take is one bad splice to lose the grounding down stream.

Following your view I guess we should run two EGCs all over the house because the NEC only requires one, that is a the minimum and one might fail.


Do you run two wire EGCs in PVC in case one fails?


Me, .... I install EMT properly with plenty of supports so I do not expect it to fall apart.

Hmmmm... never thought about it that way before. I have always pulled an EGC in emt because I considered it a good practice but at the same time would have never considered a redundant ground in a wood frame residence.

 

[Eddy Current]

It could be a local amendment.

Here in PHX. We have to use a conductor in EMT.


If you hook that "pigtail" to a Grounding conductor, you are grounding your box.

What's the good of grounding the box if its not connected to (emt) a path to ground?

 

[480sparky]

As far as the EMT v. a conductor ground issue, you may want to read Soares Book on Grounding & Bonding.

Short version: Even when using a conductor inside EMT, the EMT carries far more fault current than the conductor.

They also provide results that show EMT can be used as an EGC at further distances than a wire conductor.

 

[macmikeman]

I usually add a green when its small - 12 or 14. Unless project specs demand it for 3/0 in 2" or similar large sizes, I don't cause that costs alot more. When I do pull in an equipment ground wire though, just to be fair and keep the universe in balance, I remove all the set screws from the couplings and box connectors.......

 

[Jim W in Tampa]

What's the good of grounding the box if its not connected to (emt) a path to ground?

Thats the point, if a section opens up and they do ,then we have no ground.
Had you pulled a ground wire chances are high that we are still safe.
Now if it is ran perfect and straped and ran on building steel then yes likely be no problem.
That is the ideal world. We see the reality all the time. Take a good look when your in stores and you likely will find a section that has come loose.

All comes down to workmanship and who ran the pipe. Top men don't usually run the straight sections.

Like I said from beginning NEC does not require it. Wire is rated in amps but I yet have not seen EMT rated.

 

[LarryFine]

I have done a few parking garages and that can easily be up to 500 feet or more and that is 1,000 screws.

Wouldn't that be 100 screws?

If you were offered a system with the added ground or without and price was the same would you reject the ground wire ?

No, but I sure wouldn't offer it at the same price.

 

[LarryFine]

Wire is rated in amps but I yet have not seen EMT rated.

That's because a conduit can out-carry any conductors that they may enclose.

 

[Jim W in Tampa]

Wouldn't that be 100 screws?
No, but I sure wouldn't offer it at the same price.

OK bad fast math but point is still the same. I am first to admit I miss a screw sometimes.

 

[480sparky]

Wouldn't that be 100 screws?
.......

Could be just 50 if you used 20' sticks.

 

[Jim W in Tampa]

Could be just 50 if you used 20' sticks.

never seen a 20 do they make them ?

In that case only half the danger ?

 

[480sparky]

never seen a 20 do they make them ?

Wheatland makes it.

In that case only half the danger ?

No, just half the couplers needed.

 

[taylorp]

Why are you all arguing with Jim W? I think Jim has a valid point. The reason many designers specify an EGC installed within EMT is because of the nature of EMT. EMT depends on compression or set screw fittings. EMT is not threaded like Rigid. EMT is often the first metallic raceway to begin losing its grounding continuity due to corrosion or loose joints.

I don't think it is necesary to require an extra EGC within EMT by the NEC. The NEC lists EMT as a type of EGC in 250.118 (4) and I agree that it is. But the NEC also states in a FPN under 250.2 that "examples of ground-fault current paths could consist of any combination of equipment grounding conductors, metallic raceways, . . . ."

Any installation can have a bad connection, we are not discussing poor workmanship. We are discussing the use of EGC's within EMT.

So I don't have a problem with anyone who wants the extra EGC in EMT. Personally, I usually pull the extra EGC conductor too.

 

[Jim W in Tampa]

Why are you all arguing with Jim W? I think Jim has a valid point. The reason many designers specify an EGC installed within EMT is because of the nature of EMT. EMT depends on compression or set screw fittings. EMT is not threaded like Rigid. EMT is often the first metallic raceway to begin losing its grounding continuity due to corrosion or loose joints.

I don't think it is necesary to require an extra EGC within EMT by the NEC. The NEC lists EMT as a type of EGC in 250.118 (4) and I agree that it is. But the NEC also states in a FPN under 250.2 that "examples of ground-fault current paths could consist of any combination of equipment grounding conductors, metallic raceways, . . . ."

Any installation can have a bad connection, we are not discussing poor workmanship. We are discussing the use of EGC's within EMT.

So I don't have a problem with anyone who wants the extra EGC in EMT. Personally, I usually pull the extra EGC conductor too.

Thanks for the support
All i am saying is because of the higher chance of failure that I want the wire. If I could be certain that workmanship is perfect and not subject to damage then sure leave it out.
Very seldom see conditions like that.

 

[LarryFine]

P.T., I believe I speak for all when I say we have no problem with Jim. It's just a discussion of opinions and merits.

Nor do we have a problem with pulling an EGC in EMT if specified and/or requested, as long as we're getting paid for it.

 

[480sparky]

..............Any installation can have a bad connection, ...........

And the same can be said of every installation, not just ones where EMT is utilized.

You can have a bad connection with NM, or PVC, or MC, and the result is the same as a bad connection with EMT.

 

[roger]

EMT is often the first metallic raceway to begin losing its grounding continuity due to corrosion or loose joints.

Can you provide some data to substantiate that? Once again, I will point out article 517.13 and NFPA 99's commentary.


Roger

 

[readydave8]

I remove all the set screws from the couplings and box connectors.......

Why not just use an insulating washer like comes on sealtite fittings and a plastic lockring?

 

[macmikeman]

Why not just use an insulating washer like comes on sealtite fittings and a plastic lockring?

Um, cause it was just a dumb joke maybe????