Warm conduit and vibrating/ humming wires

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Tudmutt

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Iowa
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Electrician
I'm a new Journeyman and on my 1st project, so lacking in experience. Long story short I was out of town and my crew pulled all the home runs and branch circuits. Everything is working correctly but today I noticed the home run pipe containing the lighting hr's is very warm and the wires are humming (making a sound). I checked each phase. A phase 14 amps, B phase 14 amps and c phase 11 amps. All circuits are on a 20 amp breaker. Not sure how to begin troubleshooting this. Appreciate any advice.
 
How many circuits and/or conductors are in this conduit?

Are you certain that every circuit wire is in this one pipe?
 
Put your clamp meter around all of the conductors in the conduit if you can. You should not get a reading of any significant current. If you do get a significant reading, then there could be a problem like Larry was alluding to about all of the circuit conductors not being within the same conduit.
 
LarryFine said:
How many circuits and/or conductors are in this conduit?

Are you certain that every circuit wire is in this one pipe?
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Thats what I was kinda getting too with the neutral amperage. The OP might also try clamping around the conduit it’s self, possibly neutral fault current returning via the conduit.
 
Thank you for all the input. Theres 4 circuits total in the conduit, all circuits have their own neutral. The circuits goto the home run box and then down to the switch box,the other circuit is feeding an outlet blow the switch box.so id like to think all the conductors are in the same pipe.That's the only thing I can think of is a netrual issue.i will use your input and see what I come up with. Thank you
 
I've seen an LED driver that caused an audible hum at the panel and even at the switch. When I first heard it, thought was extremely weird. Isolated circuit by using a probe and touching individual breaker and could actually feel the hum. Hum disappeared when turning off circuit. Finally isolated back to a cheap LED someone had put in, removed the LED and hum was gone. Whatever caused the humming actually caused heating of wire and breaker, mild but noticeably higher than the ambient of the surrounding wires and breakers.
 
ptonsparky said:
Four circuits but you give only three currents. Assuming the receptacle has no load?
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The three current readings were not three loads, he was just measuring the currents on each phase at the panel. He didn't say whether the loads were divided, but with those readings they probably were.
 
I would say something is cross up a little.
Phase to grounded (netutal)should read the same at the panel location.
Put amp clamp on A netutal and shut off B. Look for change.
Then do the same for B.
Also place amp clamp around the conduit housing the conductors if current is present. Shut off all breakers for that conduit one at a time looking for change.
You may have more than one issue.

Edit, when do checking A and B remeasure C.
 
Looks like a mis-tap on A and B loads, but the neutral amps don’t add up. 7 amps are going a different path, perhaps the on the conduit itself. If you can get the the clamp around the conduit, you might see current. If so, turn off all circuits in that pipe, if the current is still there, it’s coming from another circuit, if it disappears, then the fault is somewhere on those circuits.
 
Tudmutt said:
Amp reading on the netruals
A phase 9 amps netrual
A phase hot 11 amps
B phase 9 amps netrual
B phase hot 14 amps
C phase 14 amps netrual
C phase hot 14amps
Click to expand...
Presuming loads remained steady, you have total of 32 amps on the neutrals, and 39 amps on the "hots".

If these are all properly connected two wire circuits, there is 7 amps unaccounted for, could be because of some interconnection with some other circuit, could be ground fault current through a high enough resistance to limit that current, or even some line to line current involved between the circuits in question, though that may not necessarily contribute much to the "humming". The heating mentioned may or may not be a problem depending on circumstances.

As mentioned if you clamp a ammeter around all the conductors, if you get a reading (possibly about 7 amps in this case) then it is current that is flowing outside the intended path for some reason.
 
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