many fluro ballasts buzzing all at once

tdexxx

Member
I was called to a store at which a large number, (maybe 25%), of the fluorescent ballasts began buzzing all on the same morning. The problem is both on the sales floor, where the fixtures are triple ft40 troffers and also in the receiving area where the fixtures are f32 t8s. All the affected fixtures appear to work like they normally would, with the usual brightness and no flicker. Can anybody suggest what might cause so many of the ballasts to suddenly begin buzzing all at the same time?
 

LEO2854

Esteemed Member
Location
Ma
I was called to a store at which a large number, (maybe 25%), of the fluorescent ballasts began buzzing all on the same morning. The problem is both on the sales floor, where the fixtures are triple ft40 troffers and also in the receiving area where the fixtures are f32 t8s. All the affected fixtures appear to work like they normally would, with the usual brightness and no flicker. Can anybody suggest what might cause so many of the ballasts to suddenly begin buzzing all at the same time?
Was there a good lightning storm the night before, sounds like they've been damaged from a lightning strike, just a guess.
 

kbsparky

Senior Member
Location
Delmarva, USA
Or a bad/open neutral on a multi-wire circuit. Ballasts may appear to be still working, but may be cooking inside ... (did you check the voltage?)
 

tdexxx

Member
Was there a good lightning storm the night before, sounds like they've been damaged from a lightning strike, just a guess.
There has been no recent lightning storm, and the lights were all burning normally, and so I'm thinking that a problem in the neutral seems unlikely. I did check the voltage to ground at the lighting contactors and found it to be near the nominal 277 volts with no significant voltage variation between circuits. This is a fairly big store with about sixteen 277 volt circuits dedicated to the lighting. Could this have anything to do with the emergency lighting fixtures?
 

Besoeker

Senior Member
Location
UK
I was called to a store at which a large number, (maybe 25%), of the fluorescent ballasts began buzzing all on the same morning. The problem is both on the sales floor, where the fixtures are triple ft40 troffers and also in the receiving area where the fixtures are f32 t8s. All the affected fixtures appear to work like they normally would, with the usual brightness and no flicker. Can anybody suggest what might cause so many of the ballasts to suddenly begin buzzing all at the same time?
Any new loads been installed?
 

Besoeker

Senior Member
Location
UK
But what could selectively make all the emergency fixtures buzz? Could it have something to do with the fire alarm?
If they are all buzzing and all stated doing it at the same time, it suggests something common. That's why I asked about any new loads.
How is the supply derived for the emergency fixtures?
 

tdexxx

Member
If they are all buzzing and all stated doing it at the same time, it suggests something common. That's why I asked about any new loads.
How is the supply derived for the emergency fixtures?
There are no new loads I know of, and I didn't see any variation in the voltage to ground measures among the contactor terminals. As for neutral problems, the large numbers of fixtures affected makes me think that lights on multiple circuits are affected which seems to make a neutral problem less likely. I did notice that the breakers labeled "emergency lighting" had been moved, though I assume they are still within the lighting-dedicated breaker panel, (where else?), and whatever shifting of breakers that occured happened some time ago so probably isn't to blame for this problem.

My understanding of how emergency light fixtures work in this kind of a store is that they have batteries and internal switches designed to feed the light from the battery whenever the main voltage shuts off, as would happen in a blackout or fire. In other words, the connection of an emergency fixture to a lighting circuit is identical to the connection of a non-emergency fixture. Am I wrong about that?
 

kwired

Electron manager
Location
NE Nebraska
Are all the effected luminaires on the same phase? You may have had some transient voltage problem (and it may be done and gone now) on one phase and it effected every luminaire connected to that phase.
 

Besoeker

Senior Member
Location
UK
My understanding of how emergency light fixtures work in this kind of a store is that they have batteries and internal switches designed to feed the light from the battery whenever the main voltage shuts off, as would happen in a blackout or fire. In other words, the connection of an emergency fixture to a lighting circuit is identical to the connection of a non-emergency fixture. Am I wrong about that?
I've come across two different arrangements for emergency lighting. Mostly for us, our involvement is in supplying UPS systems typically with three hours autonomy. The other we don't deal with very much. They are self contained fixtures with their own internal back up and that seems to be the arrangement you have.

If they are connected to the mains during non-emergency operation and that's when they buzz then something on the mains, possibly external to your building, could be the cause of the problem. Something generating harmonics causing mains voltage distortion could be the culprit.
 

broadgage

Senior Member
Location
London, England
A cynic like me would note that magnetic ballasts do tend to buzz without any fault or failure, it is just what they do.
If the voltage is correct and the lamps light normally then I doubt that much is wrong with the wireing, ballasts or lamps.

"new manager syndrome" perhaps ? (new manager takes over and notices and objects to, something that has been like it for years)

Or perhaps some other sound that previously masked the ballast buzz has recently been discontinued, new silent HVAC plant instaled ? background music discontinued ?
 

kwired

Electron manager
Location
NE Nebraska
A cynic like me would note that magnetic ballasts do tend to buzz without any fault or failure, it is just what they do.
If the voltage is correct and the lamps light normally then I doubt that much is wrong with the wireing, ballasts or lamps.

"new manager syndrome" perhaps ? (new manager takes over and notices and objects to, something that has been like it for years)

Or perhaps some other sound that previously masked the ballast buzz has recently been discontinued, new silent HVAC plant instaled ? background music discontinued ?
I was under the impression that these were electronic ballasts supplying F32T8 lamps, but maybe got that wrong.
 

tdexxx

Member
Are all the effected luminaires on the same phase? You may have had some transient voltage problem (and it may be done and gone now) on one phase and it effected every luminaire connected to that phase.
I unfortunately did not think to check to see if the buzzing ballasts were on the same phase. Is there some condition that might "fool" the emergency ballasts into "thinking" that an emergency existed, and if that happened could it make those ballasts buzz?
 

tdexxx

Member
A cynic like me would note that magnetic ballasts do tend to buzz without any fault or failure, it is just what they do.
If the voltage is correct and the lamps light normally then I doubt that much is wrong with the wireing, ballasts or lamps.

"new manager syndrome" perhaps ? (new manager takes over and notices and objects to, something that has been like it for years)

Or perhaps some other sound that previously masked the ballast buzz has recently been discontinued, new silent HVAC plant instaled ? background music discontinued ?
Cynicism is often justified in fact, though I don't believe it is in this case. The buzzing began suddenly and is unusually loud. You walk into that store, and you know something's wrong.
 

GoldDigger

Moderator
Staff member
If the lighting was not line to line I would first think that the service is a high leg delta and some breakers for line to neutral lighting were moved to the high leg by someone who did not know what that was.
Overload or saturation of the ballast core from high voltage could buzz a lot.

Tapatalk!
 

kwired

Electron manager
Location
NE Nebraska
If the lighting was not line to line I would first think that the service is a high leg delta and some breakers for line to neutral lighting were moved to the high leg by someone who did not know what that was.
Overload or saturation of the ballast core from high voltage could buzz a lot.

Tapatalk!
Whenever I have seen that happen they don't run for more then a few minutes, and they usually start to smell as well.

If they are electronic ballasts rated 120-277 though they possibly could work just fine this way.
 
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