VFD (well pump) causing LED Lights to glow

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Old 01-28-19, 05:25 PM
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VFD (well pump) causing LED Lights to glow

Hello all - first time posting!

So I have a new construction house in which I wanted to have a VFD control my well pump. This made for a much smaller pressure tank in my mechanical room and energy savings. The problem is that when the well pump runs some of my LED lights that are turned off will glow very very faintly. So faint that it is not noticeable during the day but is at night. No here is where it gets even stranger: I will even remove the complete light switch making sure that the positive and neutral wires absolutely have no chance of being connected and it still glows. Now LEDs, of course, can produce light with a lot less energy, but if the positive and neutral are separated how is it even possible for energy to flow across the lights?
 
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Old 01-28-19, 05:51 PM
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variable frequency drives...can induce a lot of strange wave forms(noise) and spurious capacitive/inductive voltages in your wiring. With LEDs, sometimes it may be sufficient to trigger them. Be sure the VFD and motor are well grounded...might help.
 
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Old 01-29-19, 05:44 AM
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Also, I would do some research into your belief that a variable frequency drive (VFD) saves you energy. While a VFD can save energy when compared to a continuously running motor like in agriculture or industry. But when compared to a traditional motor that turns off and in a home well system the VFD can actually consume more power. Add to that the increased up front cost and maintenance of a more complex system and odd power affects caused by the VFD you'll see why they are mainly for continuous running industrial applications.
 
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Old 01-29-19, 06:58 AM
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I would also think that AM broadcast reception would be affected? What make VFD?

I have been able to tame VFD's inside air handlers successfully, using ferrites and ac mains filters.
 
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Old 01-30-19, 08:35 PM
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VFD's

https://www.mtecorp.com/products/power-management/

This link will explain a lot about VFD filtering a lot of companies make these products, I used to use this page for a resource. A lot of the drive problems have been solved by Pulse Width Modulation PWM. Older drives that were 6 or 12 steps were a lot more noisy electrically. Noisy, meaning creating wave forms other than the sine wave.
What kind of drive are you using? PWM or other. Is the motor rated for a drive? Not all motors accept drives well.
I agree with another poster that the drive may not be all that much savings. Does your utility charge you a demand fee? If they do then the drive may help on startup,. If they do not then there is not much reason to have one. My experience is most loads, moving water or air the vfd really does not help all that much. Most pumps do nothing below 20% of rated rpm. When moving air the drive helps a tad bit cause it will remove all the heat or cold your air handler has produced.
Your statement of the LED's glowing when disconnected is beyond my reasoning with out all of the information of the situation.
 
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Old 02-04-19, 10:49 AM
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Sorry for not getting back to you all sooner, I just got the email saying I even had a reply.

As far as if I should have a drive or not, I did my math and here I am. A drive pencil out in the first year of my install. A 3-P motor is nearly 400' down in a hole and it's not coming out so changing it to a standard setup is the last pick.

The electrician did meager the ground on the pump and drive, we have a very strong path to ground so that wasn't an issue. I thought it was noise as well, but it's weird that it feeds back to the panel like that. In my experience, the noise affects the pump motor, especially over long distances. In this case, the motor is over 400' away due to being in a very deep well. The drive does have an internal EMC filter to help with that noise so I don't have motor issues. Still just very strange having it feedback into my lights, even when the positive and neutrals are physically separated. And it doesn't do it on all lights either.
 
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Old 02-04-19, 11:01 AM
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This "noise" is not usually from the motor. Its from the drive, and the nasty stuff is conducted into the AC mains. Thus, anything that is connected to the mains will be exposed to these HF voltages. LED's are quite sensitive. It takes very little energy to dimly light a LED chip.
 
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Old 02-11-19, 11:41 AM
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Electrical harmonics

The filter in the drive does nothing for your electrical feed/line. I would start with the manual for the drive and see what the mfg recommends for a 400 foot load. That is a fer piece for a drive. Not saying is wrong/or bad just it is a long ways away.
Simple test take your VOM with an HZ scale and while the drive is running check the feed wires at your electrical service. The meter is not accurate enough to give you a complete picture but it will identify the strongest harmonic. Normal would be 60hz plus or minus. EXAMPLE a reading of ~180 HZ is the 3 harmonic. A reading of ~120 is the 2 harmonic. Even harmonics you can ignore. The nasty ones are 3,5,7,9 harmonics. My experience is 5 and 7 cause most of the problems. If you measure one of the odd harmonics you can be assured that you have all of the harmonics below it. Any computer with a switching power supply or led bulb with a transformer is going to create Harmonics. They tell you in the label.
I haven't a clue why you would megger the ground. A megger is an insulation tester not a ground tester. Does the vfd location have its own ground rod? (not a good idea) The ground should be at the meter location and NOT AT THE PUMP. There is a section in the NEC about supplemental grounding but it is very confusing to apply.
Measure the voltage at the meter and at the line side of the drive on and off. Ideal would be less than 5% difference. If more then it might be time to check the mfg specs on the drive. There is a way to boost the voltage using the drive, usually. If you have a VOM that does min max recording check that at the line side of the vfd.
Please do not check any voltages on the load side to the pump with your electrical meter. Voltage close to 1000 are created by the drive and could have devastating consequences if your holding the meter. Remember your safety equipment when measuring live circuits, glasses, clean leather gloves and do not be wearing man made fibers. https://content.fluke.com/promotions...guidelines.pdf

This should help your understanding. I own a Micronta VOM I bought at Radio Shack 40 years ago. Still use it but I will not let anyone else use it as I know it is unfused and do not want to hurt some less skilled person. I had them one of my Flukes.
 
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Old 02-11-19, 11:57 AM
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I would severely doubt the VFD has any bearing on the LED's. The more likely culprit is the wiring to the well and the wiring to the LED's is in close proximity and the LED's are inductively picking up the power thru induced currents.

One way to verify this is to run the well pump with the VFD out of the line.

I have customers homes where the LED's stay lit even with the breaker off. It doesn't take much induced current to make them light dimly. On a positive note..... some manufactures are adding a snubber circuit in the bulbs to reduce this problem.
 
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