Exploding Ballasts?

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TNBaer

Senior Member
Location
Oregon
I have a customer who called me out last week to take a look at lighting situation they were having. They have some outdoor lighting around their downtown offices used as pathway lighting. This pathway lighting is in a recessed wallpack type fixture and uses 1 - 70 watt Pulse Start Metal Halide lamp.

Two weeks ago a ballast exploded. It sheared off the heads of the four screws holding the faceplate of the fixture on leaving the screws themselves still within the fixture. Then it flung the faceplate across the street about 100'. The lamp, amazingly, was left intact.

My customer chalked it up as being an odd fluke. One in a million. Then, a week later, a second ballast exploded with equally disturbing force. The lamp, this time, was not as lucky.

I have never seen a ballast explode with such force, nor heard of it happening. A quick google search gave me nothing, other than the odd CFL lamp catching fire or smoking.

Has anyone ever seen this? Any idea what could be causing it?
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Never heard of a ballast exploding. I've heard of electrolytic capacitors and other electronic devices exploding. Particullary when exposed to excessive currents, or incorrectly applied source polarity. But with a ballast I would expect some form of overcurrent protection (the branch breaker, or a internal fuse or circuit breaker) to open before an explosion happened.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Was the lamp replaced with the wrong type. I have seen a pulse start lamp do a melt down in a none pulse start fixture.
 

TNBaer

Senior Member
Location
Oregon
Was the lamp replaced with the wrong type. I have seen a pulse start lamp do a melt down in a none pulse start fixture.

No. These were nearly brand new fixtures from an extremely reputable lighting manufacturer. And, again, the lamps didn't "Non-Passively Fail", the ballasts violently exploded. What was left of the ballasts were barely recognizable as ballasts, just charred cinders.

These are recessed fixtures, mounted into brick columns and are similar to a wall pack (they are pathway lights, about 3' off the ground). I've never seen nor heard of this happening. I assume that both ballasts were from the same manufacturer since the fixtures were ordered from the factory, though I can't tell that now.
 

TNBaer

Senior Member
Location
Oregon
They explode randomly during the night. They only have exploded while they were on.

I, too, thought of some sort of moisture problem, or maybe since it is a sealed fixture some sort of gas build up.
 

Electric-Light

Senior Member
Never heard of this. Perhaps the ballast is out-gassing, then the vapor ignited from arc from thermal cut off or the winding breaking.

Do you have pics of failed ballasts? Don't toss 'em yet. Contact the manufacturer. They may want to have them sent in for evaluation.
 

jeremysterling

Senior Member
Location
Austin, TX
I repaired the aftermath of one violent ballast explosion. That was, if memory serves me correctly, in a 175W MH 277V garage lighter about six months after new install. I thought it strange at the time and, like you, chalked it up to fluke.

But two on the same install is very interesting.

edit to say, maybe it was a 100W PS
 
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TNBaer

Senior Member
Location
Oregon
I repaired the aftermath of one violent ballast explosion. That was, if memory serves me correctly, in a 175W MH 277V garage lighter about six months after new install. I thought it strange at the time and, like you, chalked it up to fluke.

But two on the same install is very interesting.

edit to say, maybe it was a 100W PS

It would certainly be interesting if it was a pulse start fixture. I wonder if this is an issue with pulse start systems? You'd think, if it were a probe start problem, we'd have heard a lot about it considering how many probe start systems there are out there.
 

WIMaster

Senior Member
Location
Wisconsin
Are you sure they are not dieing due to "high speed lead poisioning" ?

I have seen that phenomenon.

Voltage surge?

Wrong lamps installed, even manufacturers do it.
The person on the assembly line doesn't make much and often doesn't care much either especially if they are a temp.
 

kwired

Electron manager
Location
NE Nebraska
Are the ballast's in question just an open core and coil or are they an enclosed assembly containing transformer, capacitor and ignitor?

I don't see a core and coil exploding unless subject to a very high voltage like from a lightning strike. Capacitors are more subject to exploding, most of them that are separate component should have a fuse link that opens circuit before the case ruptures. If all components are in one sealed case, who knows whats in there.
 
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