EMT conduits containing feeders turning different color?

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Canton

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Electrician
I have EMT conduits runs in two different facilities that were installed in the last 2 years (New Installations). The EMT is loosing its galvanized coating and turning dark in color.

The interesting thing is that these are all feeder pipes, but only pipes that contain a neutral? The 3 wire feeders are fine just the 4 wire feeders are turning a different color....:?


Anybody know what would cause this?
 
hardworkingstiff said:
Can you give some more specifics on what the 3-wire and 4-wire feeders are feeding? Are any on them parallel circuits?
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There are some that are parallel feeders. Most are in a data center. Some are high voltage and low (480, 208). Very random, but the only thing in common is all the pipes with discoloration contain a neutral....?
 
In one of the classes I took the instructor was talking about non-liner loads and 3? power. He was saying that the current was higher and we had to account for this with conductor size.
I'm posting this for discussion because I didn't understand all of what he was saying.

Also are all the wires changing color or just the neutral? Is it the copper or the insulation? In any case I would be worried because it sure looks like the wires are overloaded. That's what I've seen change the color.
Thanks
Mike
 
Canton said:
I have EMT conduits runs in two different facilities that were installed in the last 2 years (New Installations). The EMT is loosing its galvanized coating and turning dark in color.

The interesting thing is that these are all feeder pipes, but only pipes that contain a neutral? The 3 wire feeders are fine just the 4 wire feeders are turning a different color....:?


Anybody know what would cause this?
Click to expand...

What is in the environment at each location? Any airborne chemicals or corrosive gases at either or both locations? Could be more to it than just what is inside the raceway or what is supplied. Ammonia doesn't get along with galvanized metals very well.
 
I agree with harmonics being the root cause. Should be simple enough to evaluate. The conduit is discoloring because it is getting quite warm, and you can be certain the conductor insulation has been degraded... all of them, not just the neutral... but the ungrounded conductors may not appear degraded where they emerge from the conduits.

Triplen harmonics are additive. Technically, the neutral current can be as high as the sum of all three ungrounded conductors current's magnitude... but practical limitations typically put it around two thirds.
 
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kwired said:
What is in the environment at each location? Any airborne chemicals or corrosive gases at either or both locations? Could be more to it than just what is inside the raceway or what is supplied. Ammonia doesn't get along with galvanized metals very well.
Click to expand...
It would seem corrosive influences would be exhibited on conduits without the neutral also... though it could be a combination of heat from harmonics and corrosive influences...???
 
Smart $ said:
It would seem corrosive influences would be exhibited on conduits without the neutral also... though it could be a combination of heat from harmonics and corrosive influences...???
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I won't disagree that there likely is more heat in these raceways, and possibly because of high harmonics on the neutral conductor.

Many times heat often is needed to start or speed up chemical reactions as well.
 
Thanks everyone for the input. My first thought was harmonics also, especially since it is only the feeder pipes with a neutral. I have not made a sight visit yet to see it. I am getting all this through my co-worker. I will visit the sights on Tuesday.

Both places are very clean data-centers. No Chemicals or corrosive environments.


The other thing I forgot to mention was it is only certain sections of the conduits, straight runs in particular. Where it 90's down into the panels or equipment there is no discoloration. All the runs have set-screw couplings and connectors, same manufacture of pipe. So at a coupling on a straight run it will be discolored, and after the coupling into the 90 there is no discoloration....? Very strange. All pipe was bent no prefabs.

This is why it is standing out so much because it is every other pipe or so and it stops discoloring at the coupling....?
 
Smart $ said:
I agree with harmonics being the root cause. Should be simple enough to evaluate. The conduit is discoloring because it is getting quite warm, and you can be certain the conductor insulation has been degraded... all of them, not just the neutral... but the ungrounded conductors may not appear degraded where they emerge from the conduits.

Triplen harmonics are additive. Technically, the neutral current can be as high as the sum of all three ungrounded conductors current's magnitude... but practical limitations typically put it around two thirds.
Click to expand...

Yes, I definitely want to see if the pipes are heating up.
 
I concur with the previous post...what would be the solution. Larger conductors with 200% neutral?

PJHolguin :cool:


Canton said:
Thanks everyone for the input. My first thought was harmonics also, especially since it is only the feeder pipes with a neutral. I have not made a sight visit yet to see it. I am getting all this through my co-worker. I will visit the sights on Tuesday.

Both places are very clean data-centers. No Chemicals or corrosive environments.


The other thing I forgot to mention was it is only certain sections of the conduits, straight runs in particular. Where it 90's down into the panels or equipment there is no discoloration. All the runs have set-screw couplings and connectors, same manufacture of pipe. So at a coupling on a straight run it will be discolored, and after the coupling into the 90 there is no discoloration....? Very strange. All pipe was bent no prefabs.

This is why it is standing out so much because it is every other pipe or so and it stops discoloring at the coupling....?
Click to expand...
 
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