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HPWC Conduit Hum

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A few days ago I needed to do a rare mid day charge. Normally it’s scheduled to charge overnight. Anyway, shortly after starting my mid day charge I passed through the basement and hear the conduit humming. If I placed a small amount of pressure on the conduit or the joist it’s attached to the humming would stop. After 5-7 minutes it all became pretty much quiet again.

I had my electrician over, thankfully he heard it. However he was kind of stumped and was going to ask his boss / colleagues for ideas. So, I wanted to do the same here.

Power is clean at the breaker and the charger. Car shows 250’ish Volts / 40 Amps. I have 100 AMP service.

Any help or ideas would be great! Thanks!
 
A few days ago I needed to do a rare mid day charge. Normally it’s scheduled to charge overnight. Anyway, shortly after starting my mid day charge I passed through the basement and hear the conduit humming. If I placed a small amount of pressure on the conduit or the joist it’s attached to the humming would stop. After 5-7 minutes it all became pretty much quiet again.

I had my electrician over, thankfully he heard it. However he was kind of stumped and was going to ask his boss / colleagues for ideas. So, I wanted to do the same here.

Power is clean at the breaker and the charger. Car shows 250’ish Volts / 40 Amps. I have 100 AMP service.

Any help or ideas would be great! Thanks!

Is the conduit metal or plastic?

Is the conduit well grounded (to the panel) if metal?

I am going to assume this is THHN wire in the conduit?

Do you know what wire gauge was used? What size breaker? 50a?

What all wires are in the conduit? Just the two hots and a ground for the wall connector? Is there a neutral?

So I know transformers commonly hum. It is caused by electromagnetic fields created by the alternating current in the wires. Known as 60 cycle hum.

Is the conduit securely fastened? Maybe additional strapping would help?

I have never heard of just wire in conduit humming.
 
Did you have any other big loads on the system, like an oven, electric dryer, etc, at the time. In one house we had, we would get a vibration noise/hum in conduit when we were drawing a lot of power at the same time other loads occurred. That was in the 1980s so it may have been the older wiring.
 
Is the conduit metal or plastic?

Is the conduit well grounded (to the panel) if metal?

I am going to assume this is THHN wire in the conduit?

Do you know what wire gauge was used? What size breaker? 50a?

What all wires are in the conduit? Just the two hots and a ground for the wall connector? Is there a neutral?

So I know transformers commonly hum. It is caused by electromagnetic fields created by the alternating current in the wires. Known as 60 cycle hum.

Is the conduit securely fastened? Maybe additional strapping would help?

I have never heard of just wire in conduit humming.


Pretty sure he used 6gauge wire, it runs off of two 50AMP breakers / 240V. It's a clean install. Two hot and a ground make the run. No neutral with the wall charger. My guy did another strap but its tight running along a joist. Upper right side of the box, red and black wires are the charger.

20180324_121706_1538756241631.jpeg 20180324_122524_1538756241750.jpeg


Did you have any other big loads on the system, like an oven, electric dryer, etc, at the time. In one house we had, we would get a vibration noise/hum in conduit when we were drawing a lot of power at the same time other loads occurred. That was in the 1980s so it may have been the older wiring.

I do not have a very electrical loaded house. Not really anything else going on at the same time that draws much of anything except fridge. It does go quiet after a few minutes. The raceway is about 25' but the hum is pretty localized in one spot about 3/4 way down from my panel. Any slight pressure on the conduit or the joist makes it disappear.
 
Pretty sure he used 6gauge wire, it runs off of two 50AMP breakers / 240V. It's a clean install. Two hot and a ground make the run. No neutral with the wall charger. My guy did another strap but its tight running along a joist. Upper right side of the box, red and black wires are the charger.

View attachment 341081 View attachment 341083




I do not have a very electrical loaded house. Not really anything else going on at the same time that draws much of anything except fridge. It does go quiet after a few minutes. The raceway is about 25' but the hum is pretty localized in one spot about 3/4 way down from my panel. Any slight pressure on the conduit or the joist makes it disappear.

If pushing on the conduit makes it go away I would just add more conduit straps to always put pressure on it. ;-)

I would also make sure all the couplers between conduit pieces were tight. I am wondering if a lack of well grounded conduit would allow a larger field to build up rather than draining off the induced fields?

And make sure the fitting is tight where it attaches to the panel box. I take a large flat head screwdriver and a hammer to tighten them. You want to make sure it pierces the paint on the electrical box to make sure the conduit is well grounded to the main panel.
 
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I do not have a very electrical loaded house. Not really anything else going on at the same time that draws much of anything except fridge. It does go quiet after a few minutes. The raceway is about 25' but the hum is pretty localized in one spot about 3/4 way down from my panel. Any slight pressure on the conduit or the joist makes it disappear.

Sounds pretty localized. You might want to have someone look at it for peace of mind.
 
Also, FWIW, I doubt this is any kind of a danger. As long as it is one continuous piece of wire in the conduit (no joints) then there is not much to fail.

In the super super long term vibration can wear down the insulation and cause a fault, but I highly doubt it will run for enough hours while vibrating for it to be an issue.