Using metal conduit as EGC

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Until very recently, I have been in the school of installing a ground wire in all conduits. Reason being I have seen a lot of damaged and corroded EMT.

after thinking about it some more, I realized that all of that damaged and corroded EMT was in places it really should not have been installed in the first place, and that a redundant ground wire should not be a substitution for poor installation practices.
 
electrofelon said:
Right, that is what I was trying to say. Pulling a wire egc because you are scared of loose or seperate fittings, well the egc isn't going to do anything to make up for it in many cases.
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I am just the designer, not the installer. I have no control over what happens on site with the conduit. I also have no control over inspectors who demand a ground wire, and I run into them all the time. It's not a fight I choose to fight; ground wires are cheap. Characterizing me as "scared" is a bit disingenuous.
 
ActionDave said:
That's you perrogative. Almost all the time I'm running conduit that is not underground I'm in a steel structure with steel conduit tied to steel framing members with steel fasteners and the steel is bonded to the electrical system so I'm already set up with belt, suspenders, and a spare underwear and really don't need a silly green wire to make me feel better.
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I find myself in all steel construction a lot myself. Everything you touch is well grounded.

ActionDave said:
The green to everything crowd are some of the worst IMO. They have this attitude that conduit doesn't have to be made up right because Hey, it's got the green wire, don't worry about it.
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Most the broken or rusted out raceways I ever encounter were poorly installed in the first place. Not properly secured, not arranged to drain, etc.

JFletcher said:
Until very recently, I have been in the school of installing a ground wire in all conduits. Reason being I have seen a lot of damaged and corroded EMT.

after thinking about it some more, I realized that all of that damaged and corroded EMT was in places it really should not have been installed in the first place, and that a redundant ground wire should not be a substitution for poor installation practices.
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Poor installation practices like I said above.

jaggedben said:
Well, yes, somewhat. For example, it won't rust. But the main logic is still that two is better than one.
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Well three is better then two - so where should we stop?
 
kwired said:
I find myself in all steel construction a lot myself. Everything you touch is well grounded.

Most the broken or rusted out raceways I ever encounter were poorly installed in the first place. Not properly secured, not arranged to drain, etc.

Poor installation practices like I said above.

Well three is better then two - so where should we stop?
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At two, IMO.

Redundancy is good but the probability of three parallel systems failing simultaneously is not enough lower than that for two to justify the cost. I design a lot of PV systems for seven installation crews, and although we stress workmanship we have a lot of conduit joints being installed, i.e., many potential points of failure. I sleep better having a ground wire in every conduit.
 
ggunn said:
At two, IMO.

Redundancy is good but the probability of three parallel systems failing simultaneously is not enough lower than that for two to justify the cost. I design a lot of PV systems for seven installation crews, and although we stress workmanship we have a lot of conduit joints being installed, i.e., many potential points of failure. I sleep better having a ground wire in every conduit.
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If you were building grain storage bins, elevators, and associated equipment you would sleep fine with using metal raceway as the EGC. If a raceway fitting fails, practically everything else is steel, all bolted together and there is a low resistance path regardless.

I do pull EGC through Non metallic raceways or flexible conduits at these kind of sites, mostly because NEC says so, but reality is it is not really necessary.

Slightly different topic but no point in driving ground rods at these sites either. The structure has a lower impedance to ground then a rod will ever have.
 
kwired said:
If you were building grain storage bins, elevators, and associated equipment you would sleep fine with using metal raceway as the EGC. If a raceway fitting fails, practically everything else is steel, all bolted together and there is a low resistance path regardless.
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Quite possibly so, but I'm not. A big part of what I design is rooftop PV installations on wood frame single family residences.
 
ggunn said:
At two, IMO.

Redundancy is good but the probability of three parallel systems failing simultaneously is not enough lower than that for two to justify the cost. I design a lot of PV systems for seven installation crews, and although we stress workmanship we have a lot of conduit joints being installed, i.e., many potential points of failure. I sleep better having a ground wire in every conduit.
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Depends on the system. United Airlines flight 232 suffered a fan disc failure which cut through all three redundant hydraulic lines.

Steps were taken to reduce the chances of that ever happening again, and I believe the Airbus has 4 redundant hydraulic systems.

Difference between airplanes and electricity is thay when electricity fails it may kill one person, maybe a few. When an airplane fails it usually kills a few hundred people.
 
electrofelon said:
I dont buy the loose coupling or box connector or forklift argument for as a reason to install a wire EGC at all. Think about it: Even with a wire EGC, the conduit will be the only fault path for a substantial portion of that conduit system. We could have a several hundred foot run with some pull boxes along the way. We all know and use the exception that doesnt require us to bond the box with the EGC if there are no splices. Any fault on those boxes or raceway will have to travel through them. You need to have good tight connections regardless of if there is a wire EGC or not.
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How about missing conduit? At my prior place of employment techs would regularly send around "pics of the day" and rotted away RMC and EMT were one of the top five. I remember working in a power plant where the conductors were holding up the conduit remnants, and even supporting boxes that had popped off the wall. These conditions weren't concealed, either. Just ignored.
 
gadfly56 said:
How about missing conduit? At my prior place of employment techs would regularly send around "pics of the day" and rotted away RMC and EMT were one of the top five. I remember working in a power plant where the conductors were holding up the conduit remnants, and even supporting boxes that had popped off the wall. These conditions weren't concealed, either. Just ignored.
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What does having a wire egc or not have to do with that? A wire egc isn't going to help in most of those situations.
 
electrofelon said:
What does having a wire egc or not have to do with that? A wire egc isn't going to help in most of those situations.
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Why do you say that? Of course a wire EGC wouldn't help with the conductor protection aspect of the conduit but it would bridge the breaks between intact sections of conduit for grounding.
 
ggunn said:
Why do you say that? Of course a wire EGC wouldn't help with the conductor protection aspect of the conduit but it would bridge the breaks between intact sections of conduit for grounding.
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If it faults to the conduit, the conduit is the only path anyway. Of course depending on the situation, it could go "the other way" if there is a path and pick the wire egc down the line.

I don't really plan my installations around gross incompetence, damage, lack of repairs, etc. Maybe I'll start putting larger wire in in case someone puts a larger breaker in?
 
electrofelon said:
If it faults to the conduit, the conduit is the only path anyway. Of course depending on the situation, it could go "the other way" if there is a path and pick the wire egc down the line.

I don't really plan my installations around gross incompetence, damage, lack of repairs, etc. Maybe I'll start putting larger wire in in case someone puts a larger breaker in?
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If it faults to the conduit, experience suggest this will happen in the vicinity of a device. If the device is properly connected to the EGC the fault current will flow back along the EGC. This was a known harsh environment. I don't actually recall if there was an EGC in the particular examples brought to our attention, but given the fact that conduit degradation could be expected it would have been wise to include an EGC even if not required.
 
gadfly56 said:
If it faults to the conduit, experience suggest this will happen in the vicinity of a device. If the device is properly connected to the EGC the fault current will flow back along the EGC. This was a known harsh environment. I don't actually recall if there was an EGC in the particular examples brought to our attention, but given the fact that conduit degradation could be expected it would have been wise to include an EGC even if not required.
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Yeah, I would support, and would use a wire egc in some cases, like outside with emt (this is required anyway in WA state). What I dont believe is that there should be any difference in method chosen or workmanship based in whether a wire egc is planned.
 
electrofelon said:
I don't really plan my installations around gross incompetence, damage, lack of repairs, etc. Maybe I'll start putting larger wire in in case someone puts a larger breaker in?
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I don't either. I plan them around seven installation crews, hundreds of projects per year, and Murphy's Law. That, and the fact that some inspectors will fail my inspections if a ground wire isn't there. And yeah, I know they are technically incorrect but it's not a battle I consider to be worth fighting. BTW, I am not trying to belittle or ridicule your design methodology; I would appreciate the same from you.
 
It is often more cost-effective to do things that are unnecessary but don't hurt anything rather than spend the time trying to educate somebody who doesn't want to be educated. Somehow our shop got a hold of a chart one time that showed what size wire should be used for various ampacities they decided that the ampacity meant the rating of the Upstream fuse or circuit breaker. So with many motor circuits they were making the wires a lot bigger than they needed to be. To me it doesn't make any difference if you go from a 14 to a 12. But sometimes you end up with lots of extra copper that isn't cheap and then I have to take them in hand and explain things. I think I have finally gotten most of them to the point where they understand that the ampacity has to do with how much current the motor is actually going to draw as opposed to what size the fuse or circuit breaker is but it took many years. Often, I just mark on the drawings what size wire I want used and they just do it. But if I don't mark on the drawings they sometimes go back to the old ways.

Years ago, like two or three decades, someone told one of them that it was against the electrical code to daisy chain more than 10 relays to a common. So for years they would add terminals to the terminal strip because there weren't enough terminals. I never really thought much about it because a few terminals doesn't matter any but one time I had gone through and counted all the terminals that we needed and they added like 25 more. So I got curious to find out why. It turned out that every row of devices they started a new chain. It's in the electrical code somewhere. :)

They are getting better about that kind of stuff too. I guess everybody has their little quirks. Quirks used to bother me a lot more than they do these days.
 
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ggunn said:
I don't either. I plan them around seven installation crews, hundreds of projects per year, and Murphy's Law. That, and the fact that some inspectors will fail my inspections if a ground wire isn't there. And yeah, I know they are technically incorrect but it's not a battle I consider to be worth fighting. BTW, I am not trying to belittle or ridicule your design methodology; I would appreciate the same from you.
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I am actually with you on a wire EGC for PV. Its mostly outside, and the EGC is usually not that large. These threads often go in different directions and there are several things going on a the same time. My comments were not directed at you specifically, they were more general.
 
gadfly56 said:
If it faults to the conduit, experience suggest this will happen in the vicinity of a device. If the device is properly connected to the EGC the fault current will flow back along the EGC. This was a known harsh environment. I don't actually recall if there was an EGC in the particular examples brought to our attention, but given the fact that conduit degradation could be expected it would have been wise to include an EGC even if not required.
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Also sounds like a different raceway type should have been used. Want durability of metallic - there is stainless.
 
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