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Just a couple of things to mention, code wise I think you are fine.

Design wise voltage drop is more of an issue as you load the circuit heavier.

If you break the circuits up and one has a short they don't lose all the lighting. This may not be a problem in this case but it is something to think about. We do a lot of large site lighting and we do not use one circuit to light an area, we mix the circuits up in case one circuit fails you still have light.
Like every other light..1 light phase A 1 light Phase B 1 light phase C and so on.:thumbsup:
 

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I was at a warehouse last week with 120V 30 amp lighting circuits to the HPS fixtures. All circuits carrying near the max 26 amps. All the breakers feeding the lights were over 200 degrees. This was a 225 amp GE BR style panel. Not sure if bolt in breakers would operate any cooler.
I am actually more curious about this one right here. I am currently looking at this panel with a 30a 208v circuit and each breaker is feeding 4 HPS lights, the total load on each breaker is 24.5A but they avarage around 23A this a Siemens Panel with bolt on breakers yet breakers are reading on average 190 degrees Fahrenheit and not a single one of them are tripping. they are at the 80 percent of the branch cir. and I am trying to figure out the reason for the heating.
 

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I am actually more curious about this one right here. I am currently looking at this panel with a 30a 208v circuit and each breaker is feeding 4 HPS lights, the total load on each breaker is 24.5A but they avarage around 23A this a Siemens Panel with bolt on breakers yet breakers are reading on average 190 degrees Fahrenheit and not a single one of them are tripping. they are at the 80 percent of the branch cir. and I am trying to figure out the reason for the heating.
is the wire #10 or 8 ?
 

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is the wire #10 or 8 ?
The wire is all number #10 and thought that it may be a lack of de-ration on the part of the original electrician based on code 310.15 (C) (1) on the table it shows that it should be debated by 80 percent. So wire i felt should be fine. There are 6 current carrying conductors. Now I did try and replaced a few of the circuits with #8 and those seem to be getting the same result. Tried to run a different raceway and have only one circuit in that one, using the #10 and still same result. This one is definitely got me scratching my head. Now I am starting to think that maybe 210.23 (A) may be the issue here. These HPS lights are hooked up with a nema 6-15 plug. So if I understand this righ, can’t use 30A breakers because of 210.23 (B). But can that really be the reason the breakers are heating up like that?
 

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190*F is 22* short of boiling, are you sure that is correct?

the face of the panel would be too hot to leave your hand on it, touching the breakers would actually put a blister on you!!
what is the air temperature around the panel? the ambient temp?

210.23(B) says any ONE outlet shall not exceed the 30A rating . . .as in dont put a 35 amp outlet on that circuit. your scenario is fine, its a very common set up
 

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We used 30 amp 120v for temporary lighting for many years. Then ground faults were introduced and we went back to 20 amp 120v for the sake of the breakers.
Finally ended up with temp lighting stringers with metal guards and rough service lamps.
 

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190*F is 22* short of boiling, are you sure that is correct?

the face of the panel would be too hot to leave your hand on it, touching the breakers would actually put a blister on you!!
what is the air temperature around the panel? the ambient temp?

210.23(B) says any ONE outlet shall not exceed the 30A rating . . .as in dont put a 35 amp outlet on that circuit. your scenario is fine, its a very common set up
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here is one of the circuits, this one is clocking at 177.6*f and it’s center point is at 181.4*f. It’s the only one I took a picture of. And yes. You can not keep your hand on it. Too hot to the touch.
 

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I cant find the problem with the info we have here.

Unless these lights have an electronic ballast. if this is the case, there is the probability of harmonics and other unusual problems. electronic power supplies usually put out a square wave as opposed to a normal sine wave. because of this they also produce harmonics in the return current that cant be measured with meters designed for 60Hz. the harmonics appear as amps/current flowing at other than 60Hz.

if all of this is true then you have more than 24amps flowing in the return to your breaker that you cant measure. there are meters that are designed for this, but you used to need an oscilloscope to see it.
the only remedy is to reduce your circuit load by half or maybe one third.

Let me know what you find out :)
 

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You can measure the highest Hz with your VOM. However you can not measure any of the other harmonics or the force behind them.
Long ago we used to check the neutrals at the transformers showing this during testing.
Will take a shut down and check the tightness on the grounding and bonding. Helps not to have to run a 3-4 point grounding at this time. Need an Aemc 6417 or Fluke ground testing meter (donut). Not everyone has one of those. Do not need a outage for test with those. A CT to measure the ground rod/wire and a VOM will help in the determination. Last century we would install K rated transformers, which were one size larger or so for the harmonic load on the neutral.
 

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Discussion Starter · #31 ·
Could you re-pull the feeder wires going out to the lights 1 or 2 sizes up?

Wouldn’t that disperse the heat a little more?
 

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AFIK the harmonics overheating the neutral is only an issue when you have a multiwire circuit where you size the neutral counting on the cancellation limiting the neutral current - the harmonics don't cancel. But I'd think the harmonics causing mechanical vibration is a whole different issue, it will happen whether the neutral is overloaded or not.

Depending on how the dimmer is set up you may be able to adjust it so that it doesn't reach the setting where you get the resonance, just a little higher or lower and it may no longer resonate.
1) he is on 220V circuits, no neutral, the wires are not overheating, the breaker is
2) There is no humming in this post
 

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Discussion Starter · #34 ·
1) he is on 220V circuits, no neutral, the wires are not overheating, the breaker is
2) There is no humming in this post
If the wires aren’t overheating, but the breaker is - and if that breaker is running at an amperage under what it’s rated - has the breaker been replaced yet with a new one?
 

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Could you re-pull the feeder wires going out to the lights 1 or 2 sizes up?

Wouldn’t that disperse the heat a little more?
he has already tried a rewire of one circuit with #8, the BREAKER is still overheating
the wires are NOT over heating
look carefully at the pic with the IR camera: the hottest thing there is the breaker
 
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