Blown out T8's

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Cletis

Senior Member
Location
OH
We have been pulling out a few blown out t8 bulbs (right at the ends) lately. What would be the main cause of this? Power surges or overheating ?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
We have been pulling out a few blown out t8 bulbs (right at the ends) lately. What would be the main cause of this? Power surges or overheating ?
If the "blowout" is a mechanical failure or is very early in the predicted life, I would suspect wrong ballast or socket wiring.
A breached envelope will release mercury and is not a normal failure.
Tell us more!
 

Cletis

Senior Member
Location
OH
If the "blowout" is a mechanical failure or is very early in the predicted life, I would suspect wrong ballast or socket wiring.
A breached envelope will release mercury and is not a normal failure.
Tell us more!

Not much really to tell. Just went to a facilty to change out around 500 t8's to new. We had around 5-10 that the ends where just blown out. Around 3-5" of end of bulb was just gone. Silver cap was still in socket. We a pia to get caps out. They do have power quality problems (mostly 3-5am in morning) and lot's of outages in area as well. None of bulb were totally blown, just last few inches of glass gone
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Not much really to tell. Just went to a facilty to change out around 500 t8's to new. We had around 5-10 that the ends where just blown out. Around 3-5" of end of bulb was just gone. Silver cap was still in socket. We a pia to get caps out. They do have power quality problems (mostly 3-5am in morning) and lot's of outages in area as well. None of bulb were totally blown, just last few inches of glass gone
That is an extremely unsafe result given the mercury content, and a hazmat evaluation should be made just in case.
Do not let this situation go on. Something has caused an extreme thermal shock to the bulb.
Start by double checking the ballast/bulb match, especially if the T8s were retrofitted into existing luminaires.
Possibly the old and new T8s are not a match, such as HO versus non-HO.
Or do you mean that you found damaged old T8s when doing the replacement?
 
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jeremysterling

Senior Member
Location
Austin, TX
I've heard that "instant start" ballast cause the ends to stay "hot" while the lamp is on. I see this type of T8 lamp failure frequently with IS ballast and I would say that it is normal, notwithstanding Golddigger's observation that this is a potentially hazardous condition. I see it in all manufacturers ballasts and bulbs.

I would recommend sleeves or shatterproof lamps for strips in areas where a broken lamp could drop onto someone. Troffers with lenses also prevent failed lamps from falling out of the overhead.
 

Cletis

Senior Member
Location
OH
I'm leaning towards the instant start theory as I have heard this as well keeping the anode "ON" all the time. This whole place is just a bunch of old (15-20yrs) warehouse style track lights with a hodgepodge of old magnetic ballast and new electronic ones (instant and other types). Already told owner he needs to replace all have given several estimates but not pulling trigger on it. Over 50k to take old down and new up in this place. I'll warn him of dangers and see if this helps the sale.

These are the ones i'm proposing for this application below. They are very nice...and pricey

http://www.gelighting.com/LightingW...umination-linear-suspended/overview/index.jsp

Appreciate the tips
 

kwired

Electron manager
Location
NE Nebraska
I'm leaning towards the instant start theory as I have heard this as well keeping the anode "ON" all the time. This whole place is just a bunch of old (15-20yrs) warehouse style track lights with a hodgepodge of old magnetic ballast and new electronic ones (instant and other types). Already told owner he needs to replace all have given several estimates but not pulling trigger on it. Over 50k to take old down and new up in this place. I'll warn him of dangers and see if this helps the sale.

These are the ones i'm proposing for this application below. They are very nice...and pricey

http://www.gelighting.com/LightingW...umination-linear-suspended/overview/index.jsp

Appreciate the tips

you may have answered your question in that post. With the mix of lamps/ballasts on the site - there may be many lamps not matched to the ballast in the luminaire.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
If the "blowout" is a mechanical failure or is very early in the predicted life, I would suspect wrong ballast or socket wiring.
A breached envelope will release mercury and is not a normal failure.
Tell us more!


Why I use LED. No toxins what so ever :D (ok at least that get inside you)

I've heard that "instant start" ballast cause the ends to stay "hot" while the lamp is on. I see this type of T8 lamp failure frequently with IS ballast and I would say that it is normal, notwithstanding Golddigger's observation that this is a potentially hazardous condition. I see it in all manufacturers ballasts and bulbs.

I would recommend sleeves or shatterproof lamps for strips in areas where a broken lamp could drop onto someone. Troffers with lenses also prevent failed lamps from falling out of the overhead.

Rapid start ballasts keep the filament running. Each cathode draws an extra 2 watts (4 watts per tube) to keep the heater going. Essential in dimming applications.

Instant starts works on a corona discharge principal where a very high voltage is forced onto the electrodes that forces off electrons. The result is energy savings and longer life where starts are less than 1 in 24 hours. Frequent starting like occupancy sensors causes reduces life in half.
 
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Electric-Light

Senior Member
Not much really to tell. Just went to a facilty to change out around 500 t8's to new. We had around 5-10 that the ends where just blown out. Around 3-5" of end of bulb was just gone.

What do you mean by "blown" ? If the glass actually broke, the lamps would fall out of sockets. If you meant totally blackened, that's normal when they reach the end life.
 

Cletis

Senior Member
Location
OH
What do you mean by "blown" ? If the glass actually broke, the lamps would fall out of sockets. If you meant totally blackened, that's normal when they reach the end life.

They did break, but the structure of fixture basically caught the bulb only a couple millimeters away keeping them from breaking more and falling to the floor 15ft away
 

Cletis

Senior Member
Location
OH
Long gone from job. We recycled all the bulbs. Basically some of bulbs were 3.8ft with a jagged edge. We go there often, I'll take pics next time
 
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