250.118 - using emt conduit as a ground
- Thread starter difowler1
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- Simi Valley, CA
- Location
- Simi Valley, CA
And I guess we could simply say, one is not required since we ran EMT, correct?
JAP>
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
smarty pants
There is no general rule requiring EMT to contain an EGC. There are specific conditions where it is required.
If you want to be picky 517 doesn't use the term supplement either, it just says something to the effect that the wiring method must be one that qualifies as an EGC plus you must also run an insulated EGC within that wiring method. It also only applies to branch circuits supplying patient care areas, and not necessarily everything in the health care facility.
I wonder what this thread would sound like under this scenario;
We never used EMT, or rigid conduit to clear a fault since Edison played with the first light bulb. We ALWAYS pulled a separate wire to clear a fault.
Now, someone is proposing in the current NEC we use the raceways to clear a fault to save resources.
You would NEVER get this in the codebook. And I mean, NEVER.
It's just the way humans think!
We never used EMT, or rigid conduit to clear a fault since Edison played with the first light bulb. We ALWAYS pulled a separate wire to clear a fault.
Now, someone is proposing in the current NEC we use the raceways to clear a fault to save resources.
You would NEVER get this in the codebook. And I mean, NEVER.
It's just the way humans think!
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
One problem with that is we went for some time without worrying about fault clearing at all, then went to only certain instances needed equipment grounding, and finally 1955-1960 finally started to go with EGC's required for pretty much everything, and even that took some time to catch on in some places.
I'm not sure about that.
I'll use an example that came up earlier in this thread.
"We never used NM and plastic boxes for commercial installations. We always ran it in conduit or MC cable no matter what. Now someone is proposing in the current NEC that we can use NM and plastic boxes to save resources". How dare they!!! and yes, it did get in the code book, and humans do utilize the option.
It's just the way humans are, like it or not.
JAP>
Plastic boxes/wire, and grounding are comparing apples and oranges...
Grounding is the Holy Grail of the NEC. No comparison to plastic boxes. Plastic boxes were utilize because it's cheaper. Nobody gave a hoot about saving resources when plastic came out. They wanted to save money. And, you can save money by not pulling in a ground wire in conduit. It doesn't matter...
As I said, NO WAY would this ever get into the code. NEVER! I guarantee the code will finally get rid of the conduit as an effective means to clear a fault... It's just a matter of time...
What codebook year did we not worry or care about if we cleared a fault?
david
Senior Member
- Location
- Pennsylvania
Please explain how a single fault clearing path through a single wire equipment ground is more effective than multiple paralleled paths through bonded metal conduits
That'd be an awful tall order to fill seeing as how conduit has already been proven to be a better conductor than the wire type.
Jap>
It isn't when your talking about conserving resources.
Those who don't learn how to adapt to the ever changing cost saving options that are available in the electrical industry will eventually find themselves behind the 8 ball on most project business.
Not everyone has industrial or commercial clients that will turn a blind eye to the difference in price every time.
Jap>
MAC702
Senior Member
- Location
- Clark County, NV
Agreed, but if it happens, it will be from the argument that conduit fittings might be installed improperly at many places more difficult to inspect. We've all seen conduit runs sagging years later with loose fittings.
Yes, we've all seen improperly terminated wire EGC's, too, but that will be ignored.
Wow 10 pages on a EGC in EMT!
As your self appointed resident code historian I will add that;
1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.
The photo is from the 1965 NEC.
Cheers
As your self appointed resident code historian I will add that;
1/2" EMT (properly installed to NEC minimum) has a rating of 40 Amps as an EGC, 3/4" EMT has a rating of 60 Amps, 1" EMT = 100 Amps.
The conduit sizes were part of the equipment grounding conductor sizes from at least 1930 - 1965, what is T250.122 today.
The photo is from the 1965 NEC.
Cheers
Attachments
Better yet.
Let's do an expirement.
Let's consider we're all mostly above average and are able to run conduit with all the fittings tight from beginning to end. I realize that might be a challenge,but, I feel we can do it.
Let's run 100' of 1/2" EMT straight from a panel to a 120v receptacle outlet, let's say on 2x4's or some other non conductive surface.
Now, let's pull wire to that receptacle, but, we're only going to pull 2 insulated wires a hot and a neutral in the conduit.
To add to the fun, we're going to strip about 5' of insulation off of the hot conductor at about the 50' mark so it will be sure to contact the inside of the conduit when we pull it in.
We terminate the wiring on both ends and turn on the breaker. Dead short and the breaker trips because it used the conduit as a return path.
Now we pull in a green insulated EGC,terminate it at the panel and receptacle, and turn the breaker on again, and, once again dead short and the breaker trips.
What did installing the wire type EGC do to help clear the fault? Not a damn thing.
Now, let's separate the EMT from the metal box at the receptacle end and turn the breaker back on.
Again, dead short and the breaker trips. What did the wire type EGC do to help clear the fault that time?. Not a damn thing.
Now lets leave the EMT seperated from the receptacle box, and, we're going to go back and separate every joint in the conduit by an inch simulating a shotty install and turn the breaker back on.
Hey!!! the breaker held that time even though we have a section of EMT at about the 50' mark That's energized with 120 volts. Since the seperated pipe can't clear that fault, what will our wire type EGC do to help clear that danger? Not a damn thing.
You can pull a wire type EGC and bond to your hearts content, but, depending on where the fault occurs,and where the conduit return path may have failed makes all the difference in whether or not it's actually going to help.
Jap>
Let's do an expirement.
Let's consider we're all mostly above average and are able to run conduit with all the fittings tight from beginning to end. I realize that might be a challenge,but, I feel we can do it.
Let's run 100' of 1/2" EMT straight from a panel to a 120v receptacle outlet, let's say on 2x4's or some other non conductive surface.
Now, let's pull wire to that receptacle, but, we're only going to pull 2 insulated wires a hot and a neutral in the conduit.
To add to the fun, we're going to strip about 5' of insulation off of the hot conductor at about the 50' mark so it will be sure to contact the inside of the conduit when we pull it in.
We terminate the wiring on both ends and turn on the breaker. Dead short and the breaker trips because it used the conduit as a return path.
Now we pull in a green insulated EGC,terminate it at the panel and receptacle, and turn the breaker on again, and, once again dead short and the breaker trips.
What did installing the wire type EGC do to help clear the fault? Not a damn thing.
Now, let's separate the EMT from the metal box at the receptacle end and turn the breaker back on.
Again, dead short and the breaker trips. What did the wire type EGC do to help clear the fault that time?. Not a damn thing.
Now lets leave the EMT seperated from the receptacle box, and, we're going to go back and separate every joint in the conduit by an inch simulating a shotty install and turn the breaker back on.
Hey!!! the breaker held that time even though we have a section of EMT at about the 50' mark That's energized with 120 volts. Since the seperated pipe can't clear that fault, what will our wire type EGC do to help clear that danger? Not a damn thing.
You can pull a wire type EGC and bond to your hearts content, but, depending on where the fault occurs,and where the conduit return path may have failed makes all the difference in whether or not it's actually going to help.
Jap>
You need to read my first post on this.
The question was;
IF WE ALWAYS PULLED A GROUND WIRE IN since the first days of Edison and NEVER used the raceway system to clear a fault, then, could we now say today we want to eliminate the wire and use only the conduit? I say, NO. It would NEVER pass the code gurus in today's climate.
Now, we have back data of one hundred years that conduit can be an effective means to clear a fault. But, that doesn't matter. Today, more is better and they will eliminate the conduit system for the wire in due time...
And, we are basing the grounding means of conduit on a workmanlike manner, not some trunk slammer doing moonlighting. The conduit system is an efficient means to clear a fault but we will eliminate it in due time for that precious green wire. Now, of course, IMHO!
Unlikely, metallic conduit is the better EGC and the NFPA recognizes this in NFPA 99 comentary, there is also the GEMI research.
https://steeltubeinstitute.org/steel-conduit/resources/gemi-analysis-research/
Roger
Electricity itself will never let us eliminate the conduit system as an efficient means to clear a fault.
It's going to utilize it regardless of whether a code rule ever gets put in place to add an additional green wire to it.
JAP>
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
You never seen K&T or two conductor NM cable? Obviously equipment grounding wasn't so much of a priority at one time.
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