Is this unusual?

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MichaelGP3

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Location
San Francisco bay area
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Fire Alarm Technician
I noticed one 1" conduit @ 15 degrees F warmer than it's 10 or so neighbors, all supported on unistrut 12' off the floor in a mechanical room. No shock or tingling. In this facility, the stationary engineers perform remote IR readings on the circuit breakers monthly. Could harmonics be responsible?
 
MichaelGP3 said:
I noticed one 1" conduit @ 15 degrees F warmer than it's 10 or so neighbors, all supported on unistrut 12' off the floor in a mechanical room. No shock or tingling. In this facility, the stationary engineers perform remote IR readings on the circuit breakers monthly. Could harmonics be responsible?
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Maybe a 300.20 hysteresis problem? if not whats the current on the conductors in the conduit?, whats the fill%

Put an amp probe around the conduit, any current?
Now put the amp prob around all the conductors in the conduit, if there is current, then you have a 300.3 or 300.20 problem.
 
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Normally I find with this type of problem, the neutrals are not balanced, you will probably find one or several neutrals thae are connected to more than one circuit of the same phase. This will usually increase the load on the neutral above its rated current limit.
 
This condition was reported; I was told that the circuits would be identified and tested. Haven't heard back yet regarding any findings, but will let you know.
 
I will go a step further and bet it is probably a MWBC for lighting. These usually get loaded pretty high and with continuous use that conduit is uncomfortable to touch.
 
Harmonics are a possibility.
Number of conductors in the conduit.
% of load on conductors.
All conductors from one load run in separate conduits.
Measure neutral ground current (most likely not the issue, but worth checking.)

Visual
Amp readings measuring phase and neutral current would give you an idea about harmonics.
Zero sequence readings.
 
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