Dear Fine Folks at ACC,

I have a condo where the lights (overhead, undercabinet, etc) seem to "pulse" at about 1 Hz.

The "pulse" is just a small dimming (maybe 5%), repeatedly.

I've seen them on LED bulbs, incandescent bulbs, some on dimmers, some on switches. And on various circuits throughout the condo. The incandescent bulbs seem to show the effect more than the LEDs.

My DVM, when plugged into an outlet, shows approx 120 VAC, but varies between 119-121 VAC, seemingly in time with the pulsing of the lights. However since the numbers are constantly changing, the DVM can't settle down on the "high" and "low" voltage.

I initially thought is was occurring when my HVAC was on, but once turned off, it continued. The only other thing powered on in the entire condo (other than lights) is a refridgerator which seems to be working fine.

Any ideas what it could be or what to check? Or should I call an electrician out?

Thanks in advance,
Balad

 

Put a meter into a receptacle and monitor the line voltage, for fluctuation. If it fluctuates there, monitor the mains and if you have it there call the power co.

 

Dear Fine Folks at ACC,

I have a condo where the lights (overhead, undercabinet, etc) seem to "pulse" at about 1 Hz.

The "pulse" is just a small dimming (maybe 5%), repeatedly.

I've seen them on LED bulbs, incandescent bulbs, some on dimmers, some on switches. And on various circuits throughout the condo. The incandescent bulbs seem to show the effect more than the LEDs.

My DVM, when plugged into an outlet, shows approx 120 VAC, but varies between 119-121 VAC, seemingly in time with the pulsing of the lights. However since the numbers are constantly changing, the DVM can't settle down on the "high" and "low" voltage.

I initially thought is was occurring when my HVAC was on, but once turned off, it continued. The only other thing powered on in the entire condo (other than lights) is a refridgerator which seems to be working fine.

Any ideas what it could be or what to check? Or should I call an electrician out?

Thanks in advance,
Balad

You do realize that 1HZ = 1 second? Most people would say blink onece a second than at 1HZ.


I would try to isolate the lights. Try disconnecting thinks till you kind the culprit. Remove lights and connect them to a separate circuit.


Also where do you live?

 

You do realize that 1HZ = 1 second? Most people would say blink onece a second than at 1HZ.


I would try to isolate the lights. Try disconnecting thinks till you kind the culprit. Remove lights and connect them to a separate circuit.


Also where do you live?

I live in New Orleans. And yes I know, 1Hz is 1 second. It is a very slow "pulse" about once a second. Definitely NOT rapid flickering.

I'll try what you suggested - but it's strange since I have regular incandescent bulbs, HUE bulbs, CREE LED's and LED lightstrips all "dimming" in harmony - different circuit breakers and all.... Makes me think it something in the mains.

I'll hook up something to the mains to see if it is occurring there.

 

Do you have access to a 'scope?
If so I would use a small control transformer, secondary not critical, and monitor it to see if any pulse appears.
Max.

 

Do you have access to a 'scope?
If so I would use a small control transformer, secondary not critical, and monitor it to see if any pulse appears.
Max.

Yes I do. So to understand correctly, take a transformer (say 120 prim/12 sec), plugged it in, and look at the signal across the secondary?

I'm not sure I have any small transformers.... I have an isolation transformer - could I use the scope to read the output of that?

 

Is there any heavy industry nearby?
It sounds like a period heavy load (such as motor) is causing a surge of mains current, giving a slight drop in the voltage.

I've also noticed that LED lights appear to be less sensitive to the line voltage compared to incandescent bulbs.

 

Is there any heavy industry nearby?
It sounds like a period heavy load (such as motor) is causing a surge of mains current, giving a slight drop in the voltage.

I've also noticed that LED lights appear to be less sensitive to the line voltage compared to incandescent bulbs.

No - purely residential neighborhood. I need to see if any neighbors are experiencing the same thing....

 

Yes I do. So to understand correctly, take a transformer (say 120 prim/12 sec), plugged it in, and look at the signal across the secondary?

I'm not sure I have any small transformers.... I have an isolation transformer - could I use the scope to read the output of that?

That should work.
Max.

 

That should work.
Max.

Thanks, Max. Tomorrow is Mardi Gras in New Orleans... it will be a couple of days before I recover enough to run this test!

 

I used to live in Metairie, just outside of New Orleans, and we did have line variations because of the housing development that was built with underground power distribution. That would develop all sorts of funny problems because the wires were all below the ground water level at that time. I lived half way between Airline Highway and Veterans highway, one block off of Elise.
But variations like that can also happen when an automatic tap changer goes goofy trying to adjust the line voltage. I have been gone from there since 1969, so lots of things could be different now.

 

I used to live in Metairie, just outside of New Orleans, and we did have line variations because of the housing development that was built with underground power distribution. That would develop all sorts of funny problems because the wires were all below the ground water level at that time. I lived half way between Airline Highway and Veterans highway, one block off of Elise.
But variations like that can also happen when an automatic tap changer goes goofy trying to adjust the line voltage. I have been gone from there since 1969, so lots of things could be different now.

Hey MisterBill2,

As you know, in the area of New Orleans and Metairie., things only get worse! I'll check things out as Max suggested, but I'm going to guess that's it's probably a utility problem. I had a friend in New Orleans that half of the power would go out in the house all the time. But when they turned on their electric oven, the rest of the house would turn back on. It was 1/2 of of the 240 coming from the utility pole that was intermittent. Entergy finally came out and made the appropriate repairs... What weird in my case is just a small dimming at about 1 Hz. I'll let the forum know what turns up.

 

Folks at ACC - what I love about this website is all the great questions and ESPECIALLY all the great responses and wisdom that everyone contributes. I read it several times a day and learn so much. Thank you all for reading and contributing so much! I hope one day I can offer sage advice as all the regular members do!

 

One more thought is that there must be a pulsating load some place on one side of the line, and a bit of resistance in the ground connection some place just "upstream" from that load. So that the voltage drop change on the ground side causes a small change in the line voltage. That is why, in some rural locations, the starting of the well pump makes the lights blink just a bit. And that is why the line-grounding problems that we had in Metairie were big enough to pop the filaments in an series-string heaters record player. I actually saw spikes of 170 volts on an analog meter.

 

External influences can cause a myriad of problems. While not like the 1Hz dimming, in the 70s, my computer installation would crash at 8am and 5pm every day.

A medical company had moved into the building. They had separate transformers, but turned on the equipment - wait for it - at 8am and 5pm every day.

 

External influences can cause a myriad of problems. While not like the 1Hz dimming, in the 70s, my computer installation would crash at 8am and 5pm every day.

A medical company had moved into the building. They had separate transformers, but turned on the equipment - wait for it - at 8am and 5pm every day.

Reminds me of one of my best troubleshooting triumphs. It was back in the day where you would have to boot off of a floppy disk.

I had a customer that would call me all the time complaining of boot failures. I replaced disk drive, cables, controller more than once and he tried more than one disk but still the call continued.

One day he mentioned how cold it was in the office. A light wnet one. I realized he always called on Mondays. They shut down the heat on Mondays. I also remembered about people who bought software in the winter, tried booting them fresh out of the mail box and the disk would fail. The person that wrote the article (there was no internet then ) mentioned he would let the disk warm up a bit before booting and that fixed the problem.

I asked my customer if there was a warm office in the building. He said his boss's office was a lot warmer. I asked him to put the disk in his office for about 15 minutes and try again. It worked! After that he kept the disk in a warm office. No more phone calls after that.

 

... another cost free repair that works on circuit breakers that have become somewhat aged and are not frequently exercised is to locate the responsible breaker switch and briskly turn it on and off several times. This procedure seems to improve or restore the switch conductivity to some degree ... and it doesn't cost anything to check it out.

 

Turn your Main Breaker OFF.
Now measure the incoming voltage to your home ..
L1 to N = ?
L2 to N = ?
L1 to L2 = ?
Is the Voltage still pulsing or is it steady?

Do some lights get bright, while at the same time, other lights are going dim then a bad Neutral Connection.

 

Dear ACC Friends-

Yesterday was Mardi Gras in New Orleans, so I've been out of touch with all your latest suggestions. Thank you for all the responses. I will do the recommended tests and report back to you all later this week.

Balad