Flickering Lights

[k7brown90]

I was called about flickering lights in a restaurant and initially thought that the issue would be connected to the dimmer switches but the customer stated that it is every light that is flickering. I have not ran into this issue before and I have heard that this could mean a possible issue with the service. Can I get some insight on the best way to diagnose this issue?

 

[LarryFine]

Start with: incandescent or LED? Are they on dimmers?

If LED, add one incandescent to a group of lights as a test.

 

[k7brown90]

There are two switch banks totaling 11 lutron dimmer switches. The chandeliers have halogen lights and the others are LED. All of them starting flickering simultaneously.
Could this be a loose neutral in the switch bank or a loose connection at the panel?

 

[LarryFine]

It could be almost anything. Is it a steady pattern of flicker, or random?

I would start with a voltmeter at the lighting panel main terminals.

Check line-to-line, line-to-neutral, line-to-ground, and neutral-to-ground.

 

[Little Bill]

Did you do a voltage check at the switches, lights, & panel?
How many circuits are these on?

Sorry Larry, we posted at the same time!

 

[synchro]

If all.of the switches are dimmer switches, I suggest substituting a regular switch for one of them. Then see if lights on that particular lighting circuit still blink. If it no longer blinks, then maybe the zero crossings of the AC waveform are being modulated by power line signaling from the POCO and affecting the dimmers. If it still blinks, then something is likely changing the level of the AC waveform to make the lights blink.

 

[LarryFine]

He said this is new behavior on an existing installation, so something has changed recently.

He needs to do some good old troubleshooting to find out what that change is.

 

[mopowr steve]

If the halogen lights are also flickering, I doubt that power line signaling is involved with this situation. More likely looking at a connection going bad some-where or some kind of loading anomaly.

 

[synchro]

If the halogen lights are also flickering, I doubt that power line signaling is involved with this situation. More likely looking at a connection going bad some-where or some kind of loading anomaly.

Apparently some dimmers can be affected by power line signalling.
This was mentioned here:
https://proforums.harman.com/amx/discussion/8688/get-to-know-twacs
Also, the POCO can typically modify the parameters of power line signalling remotely, and that might cause dimmer problems to occur when it didn't before.
And so if a dimmer was replaced by a a regular switch, and the halogens still blink, then power line signalling in not the issue.

 

[k7brown90]

I found that an excavator dug up the ground rods and once I reconnected the grounding electrodes the flickering stopped.
Is this a sign of a loose neutral at the main panel?

 

[synchro]

I found that an excavator dug up the ground rods and once I reconnected the grounding electrodes the flickering stopped.
Is this a sign of a loose neutral at the main panel?

That certainly sounds like there could be a problem with the neutral at its connection to its bus in the panel or upstream of there.
It might be instructive to put a clamp meter around the GEC and see what current is flowing though it. You'd expect that the ground rods would not be able to conduct very much current. But the GEC connection to a water pipe certainly could, and so that should be measured.
Are the service conductors underground? If so the excavator may have damaged them.

 

[Ravenvalor]

I might be a little bit concerned about taking some safety precautions at this point. It would not hurt to call the POCO.

 

[ptonsparky]

Connecting the rods cured the flicker? You need to dig deeper into the issue.

 

[Hv&Lv]

I found that an excavator dug up the ground rods and once I reconnected the grounding electrodes the flickering stopped.
Is this a sign of a loose neutral at the main panel?

If that truly “fixed the problem”, the problem isn’t fixed..

Call the POCO and check all the connections from the main back to the POD.