Hi, All!

The title is my question. Why do they do that please? Also, by "surge" I mean that they get brighter for just an instant.

Thanks!

Fluorescent lights are usually very stable and can take voltage changes without any indication.

Assuming you have good lamps, not old ones ready to burnout, as they can try to get brighter, then there must be a serious voltage issue causing the voltage to swell (surge).

Do you see any increase of brightness with any incandescent lamps?

Lights getting bright for short periods can be an indication of a loose neutral, sometimes in a 3 wire circuit using a shared neutral, more often a loose neutral in the service feeder, anywhere from the utility transformer through the meter or at the panel.

Loose neutrals cause a condition that creates higher than normal voltage on one leg of a 120/240 volt system, and lower than normal voltage on the other leg.

While you see some lights get bright, others may be dim.


This condition can cause 120 volt devices to be subjected to voltages up to 240 volts, and can cause serious damage, and fire, if the 120 volt device does see this abnormal voltages.

Because this condition may be the reason for the lights getting bright is cause for someone to check you system.

Hi, tkrussell!

No problems with the incandescent lamps.

Do you mean that I might be perceiving the lights to get brighter because other bulbs might be burning out?

Thanks!

Yes, that is exactly what I am saying, crazy as it may seem. When a lamps get to the end of its life, it get a bit dimmer, often not perceived right away. Then the cathode beings to erode away. I have seen lamps try to re-start themselves, sort of, and get bright, most times like a flicker, sometimes staying bright for a while.

Of course, need to be sure the incandescents are on the same circuit to rule out a open neutral connection.

A real longshot, but worth mentioning, there may be a bad connection causing the lamps to be dim, and the connection gets better, so to speak, for a bit, and the lamps go back to normal. Sounds farfetched, but possible.

The intenstity profile is a lop sided peak, but you shouldn't see that. Using a realtime intensity monitor there is a definite peak. Light output is not constant. But, you should see it.

What you can see is interference with other sources, notably TV monitors. This will be perceived as flicker. It's possible that incadesent and fluorescent in the same room could exibit the same behavior.

I do the it's nearing end of life as the best explanation.