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#2673 - 07/19/01 10:36 PM Hot pipes for lighting circuits
tajoch Offline
Member

Registered: 02/09/01
Posts: 53
Loc: Quinlan texas, usa
Hey guyz got a lighting problem for ya'll I have a lighting panel in which 11 of the 12 circuits leave the panel out of one pipe, and it's hot, all the brkrs are 20 amp, the wiring is #12, none are overloaded, I vaguely remember that nonlinear loads can mess up some types of loads, this panel has 9 ckts with hid metal halide, and 3 ckts with flurescents, (277v panel) could this be a harmonics problem????

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#2674 - 07/19/01 11:23 PM Re: Hot pipes for lighting circuits
Anonymous
Unregistered


You have 22 conductors in what size and type of pipe?

What is the ambient temperature?

Is the pipe pretty uniformly hot or is there a hot spot?

> none are overloaded,
Assuming that the circuit breakers are in working order, that probably has to be true based on the #12 takes 20 A generality.

But you have a problem. You've got over 9 conductors in one conduit and you did not derate. So just maybe they are way overloaded.

>I vaguely remember that nonlinear loads can mess up some types of loads,
On the branch side, that is a problem only when the neutrals are shared on a multiwire. In that case, the neutrals can be overloaded which means that you need to derate them even further.

Do you have 22 conductors for the eleven circuits or perhaps only 17?


To me it sounds like you need more conduits, heavier wire, and perhaps a neutral per circuit or oversized neutrals.


[This message has been edited by Dspark (edited 07-20-2001).]

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#2675 - 07/20/01 03:34 AM Re: Hot pipes for lighting circuits
electure Offline

Member

Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
Or perhaps 15 conductors?

[This message has been edited by electure (edited 07-20-2001).]

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#2676 - 07/20/01 03:57 AM Re: Hot pipes for lighting circuits
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
I check for heat a lot. The simple, quick assessment of placing a hand across the breakers in a panel says a lot.

customers can be given simple layman's terms.

Hot--Bad! Hot- Fire!

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#2677 - 07/20/01 05:45 AM Re: Hot pipes for lighting circuits
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
tajoch,

Can you give us more information? What type of wire is it, what are the loads on the circuits?

Assuming it is THHN and that you have a neutral per circuit your capacity would be down to 13.5 amps (45% of 30A) if you are anywhere near that load that explains where the heat is coming from. If you can change these wires to #10s or remove half of them you should be Ok.

Bill

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#2678 - 07/20/01 01:46 PM Re: Hot pipes for lighting circuits
Anonymous
Unregistered


Or perhaps 15 conductors?
I guess since this is apparently three phase! Would someone really run three circuits on one neutral with that type of lighting?

Perhaps his neutrals are about ready to melt their 90┬░ thermoplastic off.

Putting half the wires in another conduit won't completely solve the heat problem if the neutrals need upsizing also.

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#2679 - 07/20/01 09:38 PM Re: Hot pipes for lighting circuits
tajoch Offline
Member

Registered: 02/09/01
Posts: 53
Loc: Quinlan texas, usa
Thanx guyz, it's a 277volt lighting panel, 20amp ckts, #12 thhn, pipe is aluminum, 1 or 1-1/4, (fergot to check that)
ckt 1 is 15.1A, (9 hid fixtures)
ckt 3 is 14.9A (9 hid's)
ckt 5 is 15.5A (9 hids)
neutral for 1,3,5 6.0 amps

ckt 2 16.7A (9hids)
ckt 4 6.6A 12 flurescents
ckt 6 15.2 (9 hids)
neutral 2,4,6, 15.5a

ckt 7 13.4A (8 hids)
ckt 9 13.4A (7 hids)
neutral 14.5 amps

ckt 8 15-2 amps (9 hid fixtures)
ckt 10 15.2A (10 hid fixtures)
ckt 12 6.7A (16 flur fxts)

I didn't install it, was done by a contractor prior to my working there, the contractor was called back once to fix it, but he just made it worse

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#2680 - 07/20/01 09:41 PM Re: Hot pipes for lighting circuits
tajoch Offline
Member

Registered: 02/09/01
Posts: 53
Loc: Quinlan texas, usa
oh , the pipe is uniformly hot at least fer the first 20 feet or so that i was able to feel...

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#2681 - 07/21/01 05:54 PM Re: Hot pipes for lighting circuits
Bill Addiss Offline
Member

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
tajoch,

I would say that the heat is to be expected under the circumstances. 50% of 30 is 15A and you even have some over that.

If you can change these wires to #10s or remove half of them you should be Ok.

If you want to try an experiment take the bulbs out of 1 or 2 fixtures on each of the circuits and see what happens to the Temp of the conduit.

Bill

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#2682 - 07/21/01 06:31 PM Re: Hot pipes for lighting circuits
Resistor Offline
Member

Registered: 06/26/01
Posts: 32
Loc: Huntersville, NC USA
First I would use my Amprobe just to see if we have a bad connection which I'm sure you did. Next I would worry about the metal halides. Watts?
I used to warm up next to those things in the winter!

Bill A. another good answer in my opinion, I bet if he takes out just two halides on each circuit he will see a dramatic loss in temps on the high temp zone. But I still think it sounds like an bad conection prob. Hope he lets us know!

[This message has been edited by Resistor (edited 07-21-2001).]

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