Dimming (flickering) lights

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sfav8r

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San Francisco Bay Area
At first glance this looks like every other dimming/flickering problem you've seen. When the refrigerator or washing machine kicks on, the lights dim for a split second. When the washer is in agitating mode, they pulse. What's interesting, is the home was rewired about 4 years ago (by someone else) and appears do be done well. There was no issue until about 2-3 months ago. According to the home owner, the problems started when the house across the street did a major remodel.

My first thought was a neutral that got disturbed and is loose. However, when I got to the job, physical inspection looked good, voltage at main and sub were rock solid and there was no drop in voltage measured when the various appliances were turned on.

I remember reading awhile ago about low voltage dimmers being bothered by noise on the line, so I started checking and virtually every light in the house is on a lutron dimmer, most of which control low voltage recessed lights.

I bypassed the switch on one of the lights, and the problem went away. Repeated with another circuit with same results.

So, if it really is the dimmers that are being bothered, what is it that is bothering them? Why have they worked fine for a few years and are now having problems? Inquiring minds want to know.

I was thinking that perhaps the switches have some sort of filtering caps or something, but it seems a tad unlikely that several switches would all start to fail.

Any thoughts?

Thanks.
 
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I'm just hoping that someone will chime in here as I've had the same problem with a Lightolier Multiset pro system I installed a few years ago.
Tom
 
Is every light in the entire house that has a lutron dimmer doing the flickering? Are they all on the same phase???? Have you tried turning everything off in the house (at the breaker) except for one set of lights and the refrigerator and see if that sets it flickering. What I am getting at is perhaps there is something electronic within the house that is causing this. Start eliminating. But you probably have already done this.
 
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This is a longshot, but with all the automated meter reading, automated recloser outage reporting, and other such things being done with signals over the power lines, ....and seeing that you're in the Bay area, where energy management signals might be being sent over the lines, ... do you suppose that there's some new signals on the power company's lines that are screwing with the electronic dimmers?
 
VFD in Washer?

VFD in Washer?

New washing machines use a VFD. If so, the VFD could be rich in harmonics. Dimmers are SCR based and vary the turn-on point based on voltage. These harmonics could be affecting the dimmer. If not a VFD washer, the load variation during agitation may cause the current to vary and the voltage to dip. Again, some kind of interaction. Your voltmeter may not sample and display fast enough to see the pulsations.
 
Did anyone call the power company??

Did anyone call the power company??

Call the POCO and ask them to check all their neutral connections out on the poles, transformers, meter sockets, etc. All those places that you can not visually inspect for bad connections.:roll:
 
kbsparky said:
Call the POCO and ask them to check all their neutral connections out on the poles, transformers, meter sockets, etc. All those places that you can not visually inspect for bad connections.:roll:
Click to expand...


I agree with ken.
You mention that this may coincide with a renovation in the neighborhood. There may be a situation with the neutral at that location that is affecting the house you are working in.
 
I think the following symptom tends to bust a hole in the open neutral theories, doesn't it?
sfav8r said:
I bypassed the switch on one of the lights, and the problem went away. Repeated with another circuit with same results.
Click to expand...

I don't know what to make of this problem.
confused.gif
 
Thought I read on the Lutron website that a special model number is recommended when multiple dimmers are installed. Or, maybe that was for something else?
 
Hmmmm.... Remodeled house across the way... Motors, dimmers and flicker... Let me get out my calculator here... Hmmm.....

I would go through all the neutrals AND hots to see if any are loose, and check all the connections with at IR thermometer. Get PG&E to do the same. If you have acess to a scope, take a peek at the wave form distortion during those load fluctuations and look for rising voltage coinciding with falling voltage. Make sure your grounds and bonds are good.... (I note that you are in my nape of the woods - if this is Sunset or Richmond, bond across the water meter in the sidewalk! The sand out there aint great soil for holding up a lost noodle... And our recent rain and wind have scared up a number of lost neutral jobs for me in the last few weeks.)

If you read some of Lutrons anal lit. about sharing neutrals - it is exaspirated by not having one, or not much of one...
http://www.lutron.com/applicationnotes/360283.pdf

If you look at how these dodads work....
http://www.lutron.com/product_technical/FAQ.asp#OLE_LINK1
Changes in potential (voltage drop due to load or resistive connection) will slightly change the amout of "On time" because the control voltage at the triac changes slightly during the highest load.
 
Electronic vs magnetic

Electronic vs magnetic

Another thought-- You mentioned that they are low voltage lights. If they have electronic transformers powering the lights, then they should have electronic dimmers. Now I have hooked up electronic transformers from a low voltage fixture on the standard dimmer and they worked just fine, however I was told it may cause problems with them not lasting very long, etc. I have not had this problem but perhaps along with some type of interference this may be caused by the wrong dimmers. Unfortunately electronic dimmers are quite pricey. Just a thought.
 
Dennis -
I appologize for excessive denseness.

Dennis Alwon said:
... If they have electronic transformers powering the lights, then they should have electronic dimmers. ...
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What is an "electronic transformer"? Is that a switching mode power supply?

"Electronic dimmer"? I don't think I've seen one in the last 20 years that wasn't - so I thinking you mean something different.

carl
 
Carl, a special kind of dimmer is required for low voltage dimming.

Check out this link, and look for the
ELV.jpg
icon through the page.

Edit to add: Check out Lutron's small dimming basics PDF for some more info. To be honest, I'm not sure what the deal is, but I guess it matters.
 
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Thanks for all the suggestions.

With regard to the comments about open neutrals, etc, that is where I started looking originally. As George commented, the fact that I can bypass the dimmers and eliminate the problem tends to discredit that theory. I put a data logger on the sub panel and the voltage was rock solid.

I'm sorta liking the "some kind of noise on the line" theory, the only thing is I'm not sure why it would only happen during the cycling of the fridge and the agitation of the washer. I suppose it could be some new device in the house (or nearby) in conjunction with these appliances, but I find problems are generally not that convoluted. (not that they don't happen that way sometimes)

I didn't check harmonics while I was there, I probably should have. Just for fun, I was going to try a couple different brands of dimmers t see what happens. When I get enough new things to try, I'll head back over there.
 
coulter said:
Dennis -
I appologize for excessive denseness.


What is an "electronic transformer"? Is that a switching mode power supply?

"Electronic dimmer"? I don't think I've seen one in the last 20 years that wasn't - so I thinking you mean something different.

carl
Click to expand...
No need to apologize --
Lutron has electronic dimmers that are specially designed for low voltage fixture that use solid state transforming. Check out Lutron.com
 
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Have you:

1. Using a min max multimeter recording the voltage at the panel and at the load?

2. Are the refrig and washer on the same line as the lights?

3. Moved one of the affected circuits to another line at the panel?

4. Is their distinct timing of this flicker?

5. Have you performed a FOP (Fall of Potential) test from the line conductor termination connectors in the main panel to the load conductor termination connection on the CB? This will check for loose connection on the bus, loads must be on for this to work.

6. Are you sure it is the washer and/or refrigerator? I recently did a flicker call to a new residence everyone blamed the refrigerator and washer, turned out to be a new style septic system that recycles the water through a series of filters.
 
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sfav8r said:
With regard to the comments about open neutrals, etc, that is where I started looking originally. As George commented, the fact that I can bypass the dimmers and eliminate the problem tends to discredit that theory. I put a data logger on the sub panel and the voltage was rock solid.

I'm sorta liking the "some kind of noise on the line" theory, the only thing is I'm not sure why it would only happen during the cycling of the fridge and the agitation of the washer. I suppose it could be some new device in the house (or nearby) in conjunction with these appliances, but I find problems are generally not that convoluted. (not that they don't happen that way sometimes)

I didn't check harmonics while I was there, I probably should have. Just for fun, I was going to try a couple different brands of dimmers t see what happens. When I get enough new things to try, I'll head back over there.
Click to expand...

There would have to be some sort of voltage drop/rise or it would not be happening IMO. Dimmers (especialy if dimmer more than 25%) will be more sensitive to these fluctuations than a solidly connected switch, as they tend to amplify the effect the more the load is dimmed. They can often act as a tell-tale, which why many here are looking at the neutral. But any resistive connection hot or neutral could have the same effect.

More on subject....
http://www.mikeholt.com/mojonewsarchive/All-HTML/HTML/Lights-Flicker-(Dim)-When-AC-Starts~19991007.php

Q. My lights dim every time I turn on the washing machine or other equipment. What should I do?
  1. It’s normal for your lights to dim when things that use a lot of electricity — such as your washer — first turn on. Frequent dimming, though, may indicate of a bad connection in the house wiring or a problem with PGE equipment. Call our repair number,~ to verify that PGE equipment is in working order. If it is, call an electrical contractor to inspect your wiring.
Click to expand...
http://www.portlandgeneral.com/home/products/surge/faq.asp?bhcp=1

http://www.pge.com/docs/pdfs/biz/power_quality/pq_home.pdf

If your meter or logger is not sensitive enough to recongnize voltage fluctuation try measururing the current instead...
 
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Oh, just though of something.... Should have remembered this.... I got a new washer a few months ago, and thought it made a wierd noise. (Sounds like the Tartus - for those that watch Doctor Who.) Anyway, newer designs dont have transmissions anymore - direct drive motor... Starts one way, then starts again in the other... The effect is different in that it has starting current in each direction rather than a single starting current at the cycle. But my lights don't dim though....
 
brian john said:
5. Have you performed a FOP (Fall of Potential) test from the line conductor termination connectors in the main panel to the load conductor termination connection on the CB? This will check for loose connection on the bus, loads must be on for this to work.
Click to expand...

Brian, is that FOP for inside wiring circuits similar to a voltage drop reading taken with a load tester?

By gator clipping these segments of line impedance with my cheep 15A load tester (150vac max), using phase-to-neutral --one line at a time--, shouldn't we be reading the same fall off potentials (V-drop)?

We should suspect equipment segments that exceed Tbl.9, textbook-impedance values for size & length, unless a high-Z condition could be traced upstream all the way back thru meter to service entrance, which would require POCO repair.
 
Couple of things to consider:

1) If POCO has local power distribution, then the neighbors new dimmers will interact with the dimmers in the house you are working on.

2) If the neighbor put in one of those in-line instant water heaters, then your voltage is gonna go bonkers! My brother recently put in one of those water heaters and immediately started tripping his 200A main. So he put in a 400A service. The POCO did not change a thing on the local distribution. So now his (and all of his neighbors) lights flicker like crazy every time he runs hot water!!!!
 
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