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Discussion Starter · #1 ·
It’s the second time I have ran into this in the last three years. Neutral bar humming real loud under minimal LED load.
Today I walked into check out the panel the customer was complaining about..... Humming to beat hell, I opened the panel and while I had it off I hear a thud above the drop ceiling and it immediately reminded me of a contactor.
As soon as I heard the thud the noise on the neutral bar went way down in noise level.
Sure chit I popped a tile and there was a contactor used to turn 3 circuits on/off to the building exterior lights.
Checked all around the building and it was a mix of new and retro fitted LED wall packs and shoe boxes.
The customer wants to change the panel out to get rid of the noise, I told him the new one is going to do the same thing.
I told him I think it is the type of load on the circuit causing this.
Any thoughts?
Panel looked fine, hardly any other load on it.
The other time I ran into this was on some LED track lights in a clothing store. When the lights were dimmed down it sounded like a bee hive.


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We have been getting RF noise due to LED power supplies made by certain manufacturers bleeding noise to planeside from light fixtures with pilots complaining after installation of retrofits in terminal. That’s on the Facilities Maintenance side. In my present role of Airport Communications Technician / Ground Radio Tech we get LED power supply noise in our Supertugs. So there’s that.. I believe Phillips claims there LED’s are clean and noise free. FWIW.


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It’s the second time I have ran into this in the last three years. Neutral bar humming real loud under minimal LED load.
Today I walked into check out the panel the customer was complaining about..... Humming to beat hell, I opened the panel and while I had it off I hear a thud above the drop ceiling and it immediately reminded me of a contactor.
As soon as I heard the thud the noise on the neutral bar went way down in noise level.
Sure chit I popped a tile and there was a contactor used to turn 3 circuits on/off to the building exterior lights.
Checked all around the building and it was a mix of new and retro fitted LED wall packs and shoe boxes.
The customer wants to change the panel out to get rid of the noise, I told him the new one is going to do the same thing.
I told him I think it is the type of load on the circuit causing this.
Any thoughts?
Panel looked fine, hardly any other load on it.
The other time I ran into this was on some LED track lights in a clothing store. When the lights were dimmed down it sounded like a bee hive.


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So what was the neutral bar humming? 😎
 

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Have you measured the Neutral for voltage, and HZ?
A lot of harmonics can be generated by switching power supplies.

Quick check measure HZ

If the number is 120, 240, 480 HZ not much you can do about it.
If the number is 90,270, 360 HZ then you into odd harmonics and you need a better measuring device.
Changing the panel out will not solve the problem.
 

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Discussion Starter · #13 ·
Have you measured the Neutral for voltage, and HZ?
A lot of harmonics can be generated by switching power supplies.

Quick check measure HZ

If the number is 120, 240, 480 HZ not much you can do about it.
If the number is 90,270, 360 HZ then you into odd harmonics and you need a better measuring device.
Changing the panel out will not solve the problem.
No, I would of never thought of that. How the heck to you check hertz?


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I've heard some really loud humming on Transformers when they are feeding just lighting loads. It's harmonics from what I've read.

Never heard it in a panel thou !
Probably harmonics, I know there is the oversized neutral to deal with them but never heard a panel hum because of them.
 
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