Sanity check- EGC required for feeders?

[greenspark1]

I always run a dedicated wire EGC with my feeders but recently encountered a theater building that does not have wire EGCs and uses EMT instead. 250.118 appears to allow this, but it doesn't sit right with me. The system is 208/120V 4W.

 

[ActionDave]

It is fine, safe, and up to code.
There are panels that I work on that are all EMT that don't have an EGC buss in them.

I don't pull a green unless someone makes me.

 

[kwired]

I always run a dedicated wire EGC with my feeders but recently encountered a theater building that does not have wire EGCs and uses EMT instead. 250.118 appears to allow this, but it doesn't sit right with me. The system is 208/120V 4W.

Correct 250.118 does permit it. The resistance of a metal raceway is likely going to be less then your 250.122 sized (wire) conductor pulled in there, some still like to utilize a (wire) conductor in case of a compromised connection at a fitting - though conductor terminations can also be compromised. If in a situation where you have metal conduits all racked in same assemblies - you have a pretty solid path in all the components of that rack - it is when you leave that rack that you start limiting the path and need to worry more about loose fittings - JMO on the last part there.

 

[greenspark1]

Thanks for the quick responses.

I like using a wire EGC because then it's easy to verify at each end if it's attached and connected. With conduit it's easier to have a loose joint somewhere that is impossible to find without walking each foot of the conduit. Also, with non-licensed electricians doing the work the wire EGC is easy to check, harder to tell if the EMT/RMC is continuous throughout.

If I was working in a campus or industrial type facility where there are good standards and conduit is easily accessible I wouldn't object to using the raceway as the EGC.

This reminds me of the debate of ground plug up or down in a receptacle.

 

[charlie b]

If I may be allowed to split a hair, the title you used for this thread has an error. You are discussing the Equipment Grounding Conductor (EGC). The thread's title seems to imply you are interested in the grounded conductor, which is most often also called the neutral wire. Although the code does allow certain raceways to serve as the EGC, the client requirements for every project I have designed in the past ten years have explicitly stated that they wanted a wire-type EGC within the raceway.

 

[greenspark1]

Yes you're entirely correct charlie, good catch. Edit-I don't see a way to change the title now.

I do find it interesting to discuss the WHY behind the Code requirements (raceway permitted as EGC), vs client requirements/specs (separate wire). Any input there Charlie?

 

[charlie b]

I corrected the title for you. I guess you have to be a moderator to be able to do that.

I think that clients want a wire-type EGC for liability purposes. They don't want to be exposed to the risk of a lawsuit in the event that a conduit connector gets loose and prevents the conduit from functioning properly as an EGC.

 

[kwired]

I almost commented on the thread title as it had me thinking the wrong thing at first, but I figured out what the question was and kind of disregarded it after that.

As far as client or even designer specs - you can design beyond the minimum standards of the code as it could give better performance for specific conditions. One could specify RMC even though EMT is suitable for the job.

 

[greenspark1]

Agreed, you can always design above the Code requirements. But it sounds like some/many people think that using metal conduit as the EGC is actually better than a wire EGC. That is the discussion that I am interested in hearing the pros/cons about. I would hope that the EC community could come to a consensus about the preferred method. Then each EC can have a discussion with the client about whether they want to pay for it or just meet Code.

 

[fmtjfw]

Belt and suspenders -- The metallic conduit may well be a better conductor. However a EGC wire probably does not suffer from having a splice every 10 feet. Just as I would avoid splicing the neutral or hot every 10 feet; I might prefer not to "splice" the equipment grounding method every 10 feet.

 

[Pharon]

The metal conduit should be bonded at both ends anyway, even if you run a separate insulated EGC. It's not an 'either-or'. It's a question of whether or not you are able to sleep at night with having only the integrity of the fittings guaranteeing you a fault return path.

Personally, I'll include the insulated EGC's as added insurance every day of the week.

 

[paul]

The metal conduit should be bonded at both ends anyway, even if you run a separate insulated EGC. It's not an 'either-or'. It's a question of whether or not you are able to sleep at night with having only the integrity of the fittings guaranteeing you a fault return path.

Personally, I'll include the insulated EGC's as added insurance every day of the week.

Why?

 

[GoldDigger]

What is better about insulated?
(For general purpose, that is. Pools are a different matter.)

 

[Pharon]

Why?

Which part of my explanation was confusing to you?

What is better about insulated?
(For general purpose, that is. Pools are a different matter.)

Insulated, not insulated - no difference to me. Didn't mean to muddy the waters on that one. As long as it's dedicated.

 

[iceworm]

... Insulated, not insulated - no difference to me. Didn't mean to muddy the waters on that one. As long as it's dedicated.

I'm a fan of insulated. I have anecdotal evidence that some faults (conductor damaging sized faults) can cause the bare EGC to stick to the side of the conduit. Makes the bundle really hard (or impossible) to pull out. The stuck EGC can break off inside. Conduit is useless for a re-pull unless one can get a mandrell through and knock out the stuck pieces.

I've only seen it happen twice (in 45 years). Maybe that is not often enough to matter - Still, not much extra money to use insulated.

ice

 

[GoldDigger]

I'm a fan of insulated. I have anecdotal evidence that some faults (conductor damaging sized faults) can cause the bare EGC to stick to the side of the conduit. Makes the bundle really hard (or impossible) to pull out. The stuck EGC can break off inside. Conduit is useless for a re-pull unless one can get a mandrell through and knock out the stuck pieces.

I've only seen it happen twice (in 45 years). Maybe that is not often enough to matter - Still, not much extra money to use insulated.

ice

Does it pull better than uninsulated?

 

[iceworm]

Does it pull better than uninsulated?

If you mean "pull out":
Anecdotal evidence suggests that, under conductor damaging faults, insulated EGC won't stick to the side of the conduit. One can pull this bundle out without the ecg breaking off as it does when the egc is stuck to the side on the conduit.

If you are curious why I am being wimpy: It's cause a sample of two is not a lot of test data.

ice

 

[kwired]

Agreed, you can always design above the Code requirements. But it sounds like some/many people think that using metal conduit as the EGC is actually better than a wire EGC. That is the discussion that I am interested in hearing the pros/cons about. I would hope that the EC community could come to a consensus about the preferred method. Then each EC can have a discussion with the client about whether they want to pay for it or just meet Code.

I am fairly confident in my installations, but I am a one man crew most of the time and pay attention to details. If I were running a crew even as little as three or four guys - I may not trust they will pay as close attention to details and may forget to tighten fittings sometimes, and would maybe prefer a wire EGC in the raceway just in case.

Also depends on conditions of the installation. I do a lot of work at grain storage facilities. Everything is steel and raceways are attached to it. If you should happen to have a loose fitting- the structure is even less resistance then the raceway - I am not too concerned about not having sufficient low impedance path to interrupt a ground fault in this kind of application. Same goes for a steel structured building with racks of unistrut holding your raceways - one loose fitting in the rack is not going to introduce any impedance to a ground fault - that rack and the raceways in it are all lower impedance then one raceway alone or even an EGC pulled through one of those raceways.

 

[ActionDave]

Belt and suspenders -- The metallic conduit may well be a better conductor. However a EGC wire probably does not suffer from having a splice every 10 feet. Just as I would avoid splicing the neutral or hot every 10 feet; I might prefer not to "splice" the equipment grounding method every 10 feet.

So I'm up in a lift running some EMT. I have steel i-beams up to steel cross beams that support steel bar joists that are capped by a steel roof deck. I have multiple runs of conduit going back to the panel that is mounted to steel studs. I use metal tie wire or steel one hole straps for securing. The ceiling grid is steel and is suspended from the steel bar joists with steel wires, more steel studs up to the roof deck, more steel i-beams.... Who needs fittings anyway? Well, they keep things lined up so it is easier to shove a fishtape in.

I guess I can pull a green so I can brag about how great of a guy I am, but I'm humble and a bit of a spendthrift so I don't.

 

[ActionDave]

...It's not an 'either-or'. It's a question of whether or not you are able to sleep at night with having only the integrity of the fittings guaranteeing you a fault return path.....

Sleep just fine.

That's not entirely accurate. My sleep does get disturbed, but it's not about lack of a wire EGC in conduit. Most likely it's because I have to take leak.