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MH Bulb:Exploded View
- Thread starter Superstone
- Start date
edited : bummer, that really shouldn't happen by it's self.
I went down to a dark veg room last week myself. A 1000MH had blown but stayed contained inside the bulb itself, just the innner tube exploded. Never had a bulb go out ever so it was only a matter of time. Ballast is unhooked and going in for checkups and maintenance just in case.
Superstone
Member
Also don't skimp on timers for your lights.Only use tork 1104,Intermatic T101,etc....Any mechanical timer mounted in a grounded metal box will be fine.Don't settle for anything less.
Back in the spring of 2000... I remember it like it was yesterday... I came home from work and went immedietly to the growroom like I always do.That day things were a little dark and the smell of electricity and burnt plastic filled the air. I was scared shitless and almost fainted when I realized the severity of this blow to my senses.
What happened was my cheap plastic timer got stuck,blew the fusable switch on my ballast,caught the timer on fire,and melted the electrical outlet.Luckily the circuit breaker switched off fast enough and saved the day...
This particular grow was in the attic where everything was surrounded by carpeting and wood.I've learned alot since then and now grow only in the basement where everything is surrounded by bricks,cinderblocks,cement board and metal.
EVERYBODY PLEASE BE SAFE!!!
Back in the spring of 2000... I remember it like it was yesterday... I came home from work and went immedietly to the growroom like I always do.That day things were a little dark and the smell of electricity and burnt plastic filled the air. I was scared shitless and almost fainted when I realized the severity of this blow to my senses.
What happened was my cheap plastic timer got stuck,blew the fusable switch on my ballast,caught the timer on fire,and melted the electrical outlet.Luckily the circuit breaker switched off fast enough and saved the day...
This particular grow was in the attic where everything was surrounded by carpeting and wood.I've learned alot since then and now grow only in the basement where everything is surrounded by bricks,cinderblocks,cement board and metal.
EVERYBODY PLEASE BE SAFE!!!
Superstone
Member
My safety glass saved my ass today.
Sounds like it was either run too long, or came with manufacturer defects in the arc tube... 70-700psi inside there.
End of life behaviour
At the end of life, metal-halide lamps exhibit a phenomenon known as cycling. These lamps can be started at a relatively low voltage but as they heat up during operation, the internal gas pressure within the arc tube rises and more and more voltage is required to maintain the arc discharge. As a lamp gets older, the maintaining voltage for the arc eventually rises to exceed the voltage provided by the electrical ballast. As the lamp heats to this point, the arc fails and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. This causes the lamp to glow for a while and then goes out, repeatedly. In rare occurrences the lamp explodes at the end of its useful life.[3]
Modern electronic ballast designs detect cycling and give up attempting to start the lamp after a few cycles. If power is removed and reapplied, the ballast will make a new series of startup attempts.
Risk of lamp explosion
All HID arc tubes deteriorate in strength over their lifetime because of various factors, such as chemical attack, thermal stress and mechanical vibration. As the lamp ages the arc tube becomes discoloured, absorbing light and getting hotter. The tube will continue to become weaker until it eventually fails, causing the breakup of the tube.
Although such failure is associated with end of life, an arc tube can fail at any time even when new, because of unseen manufacturing faults such as microscopic cracks. However, this is quite rare. Manufacturers typically "season" new lamps to check for manufacturing defects before the lamps leave the manufacturer's premises.
Since a metal-halide lamp contains gases at a significant high pressure, failure of the arc tube is inevitably a violent event. Fragments of arc tube are launched, at high velocity, in all directions, striking the outer bulb of the lamp with enough force to cause it to break. If the fixture has no secondary containment (e.g. a lens, bowl or shield) then the extremely hot pieces of debris will fall down onto people and property below the light, likely resulting in serious injury, damage, and possibly causing a major building fire if flammable material is present.
The risk of a "nonpassive failure" of an arc tube is very small. According to information gathered by the National Electrical Manufacturers Association (www.nema.org), there are approximately 40 million metal-halide systems in North America alone, and only a very few instances of nonpassive failures have occurred. Although it is not possible to predict, or eliminate the risk, of a metal-halide lamp exploding, there are several precautions that can be taken to reduce the risk:
* Using only well designed lamps from reputable manufacturers and avoiding lamps of unknown origin.
* Inspecting lamps before installing to check for any faults such as cracks in the tube or outer bulb.
* Replacing lamps before they reach their end of life (i.e. when they have been burning for the number of hours that the manufacturer has stated as the lamp's rated life).
* For continuously operating lamps, allowing a 15 minute shutdown for every 7 days of continuous operation.
* Relamp fixtures as a group. Spot relamping is not recommended.
Also, there are measures that can be taken to reduce the damage caused should a lamp fail violently:
* Ensuring that the fixture includes a piece of strengthened glass or polymeric materials between the lamp and the area it is illuminating. This could be incorporated into the bowl or lens assembly of the fixture.
* Using lamps that have a reinforced glass shield around the arc tube to absorb the impact of flying arc tube debris, preventing it from shattering the outer bulb. Such lamps are safe to use in 'open' fixtures. These lamps carry an "O" designation on the packaging reflective of American National Standards Institute (ANSI) standards.
http://en.wikipedia.org/wiki/Metal-halide_lamp
http://www.nasa.gov/offices/oce/llis/0309.html
End of life behaviour
At the end of life, metal-halide lamps exhibit a phenomenon known as cycling. These lamps can be started at a relatively low voltage but as they heat up during operation, the internal gas pressure within the arc tube rises and more and more voltage is required to maintain the arc discharge. As a lamp gets older, the maintaining voltage for the arc eventually rises to exceed the voltage provided by the electrical ballast. As the lamp heats to this point, the arc fails and the lamp goes out. Eventually, with the arc extinguished, the lamp cools down again, the gas pressure in the arc tube is reduced, and the ballast can once again cause the arc to strike. This causes the lamp to glow for a while and then goes out, repeatedly. In rare occurrences the lamp explodes at the end of its useful life.[3]
Modern electronic ballast designs detect cycling and give up attempting to start the lamp after a few cycles. If power is removed and reapplied, the ballast will make a new series of startup attempts.
Risk of lamp explosion
All HID arc tubes deteriorate in strength over their lifetime because of various factors, such as chemical attack, thermal stress and mechanical vibration. As the lamp ages the arc tube becomes discoloured, absorbing light and getting hotter. The tube will continue to become weaker until it eventually fails, causing the breakup of the tube.
Although such failure is associated with end of life, an arc tube can fail at any time even when new, because of unseen manufacturing faults such as microscopic cracks. However, this is quite rare. Manufacturers typically "season" new lamps to check for manufacturing defects before the lamps leave the manufacturer's premises.
Since a metal-halide lamp contains gases at a significant high pressure, failure of the arc tube is inevitably a violent event. Fragments of arc tube are launched, at high velocity, in all directions, striking the outer bulb of the lamp with enough force to cause it to break. If the fixture has no secondary containment (e.g. a lens, bowl or shield) then the extremely hot pieces of debris will fall down onto people and property below the light, likely resulting in serious injury, damage, and possibly causing a major building fire if flammable material is present.
The risk of a "nonpassive failure" of an arc tube is very small. According to information gathered by the National Electrical Manufacturers Association (www.nema.org), there are approximately 40 million metal-halide systems in North America alone, and only a very few instances of nonpassive failures have occurred. Although it is not possible to predict, or eliminate the risk, of a metal-halide lamp exploding, there are several precautions that can be taken to reduce the risk:
* Using only well designed lamps from reputable manufacturers and avoiding lamps of unknown origin.
* Inspecting lamps before installing to check for any faults such as cracks in the tube or outer bulb.
* Replacing lamps before they reach their end of life (i.e. when they have been burning for the number of hours that the manufacturer has stated as the lamp's rated life).
* For continuously operating lamps, allowing a 15 minute shutdown for every 7 days of continuous operation.
* Relamp fixtures as a group. Spot relamping is not recommended.
Also, there are measures that can be taken to reduce the damage caused should a lamp fail violently:
* Ensuring that the fixture includes a piece of strengthened glass or polymeric materials between the lamp and the area it is illuminating. This could be incorporated into the bowl or lens assembly of the fixture.
* Using lamps that have a reinforced glass shield around the arc tube to absorb the impact of flying arc tube debris, preventing it from shattering the outer bulb. Such lamps are safe to use in 'open' fixtures. These lamps carry an "O" designation on the packaging reflective of American National Standards Institute (ANSI) standards.
http://en.wikipedia.org/wiki/Metal-halide_lamp
http://www.nasa.gov/offices/oce/llis/0309.html
Another good way to do it is to get a contactor/relay (basically an electrical switch). You can get them in NO (normally open), NC (normally closed), or a combination of the two (which, incidentally, is the type you would use for a flip-flop).
NO close when voltage is applied to the coil, completing the circuit. NC breaks the circuit when voltage is applied. (These both have interesting uses if you think about it...)
You can get them in a variety of sizes, amperages, and coil voltages (meaning the voltage needed to activate it, 110-120 is the common house voltage in the US).
This will put hardly any load on the timer,(it takes a few watts to keep the coil activated, but nothing in comparison to even a 20w CFL) preventing it from failing in a spectacular fashion like you had happen to you, and making it last a lot longer. You can also use a 110/120V timer to control a 220/240V load, use a digital timer, use a cheap timer if need be, etc.
There are ready made versions available, but they're really not terribly hard to build yourself if you're halfway intelligent, and there are plenty of tutorials available online.
EDIT: Also, another reason that bulbs will fail like that is oil from your skin. I've replaced LOADS of bulbs that blew up in a short time after installation for that very reason. The oil or whatever on the bulb concentrates the light/heat at that point on the glass, causing a crack or an exploded bulb.
Make sure to ALWAYS clean your bulbs with isopropyl alcohol, dry well, and install using clean gloves. You would be surprised how many electricians don't even know about that, much less laymen (I estimate 49 out of 50 electricians I've explained that to, had no idea).
Last edited:
aggregatebuzz
Member
no fire damage thank goodness
I not sure I like those Agrosun bulbs,because they are expensive is the main reason though
I not sure I like those Agrosun bulbs,because they are expensive is the main reason though
damn. i have never had that happen and i been growing quite a while. guess my turn will come someday. i have toasted a few cheapass timers tho
I personally cannot stand those "pin" timers. This is what I use.
http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053
http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053
I had this same thing happen about 2 weeks ago with a 1000w AgroSun Cool MH bulb. I feel ya man, it sucks. The clean up is the worst part. I always make sure I clean bulbs with iso and wear gloves and it still happened. I guess certain MH bulbs are more prone to this. I got a replacement and all is well.
Why would anyone rate that as "not helpful"??
That's what makes the world go round bro, if we all agreed on everything it would be a dull place.
G
greenmatter
I personally cannot stand those "pin" timers. This is what I use.
http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053
nice ....... i wonder if they make a 20 amp model .... that one would be great for filters, fans and light movers. good post.... thanks
This one blew due to incompatibility with a digital ballast , only a 600 sodium but one hell of a bang , a 1000 w halide must have been a lot worse.
Worked replaceing street lamps many years ago , all new bulbs were washed in distilled water , wiped dry with a clean cloth then wiped with ISO or Trike and not touched with bare skin again.
The water was to remove any salt residues from sweaty fingers , was told it could weaken the glass at running temps .
Worked replaceing street lamps many years ago , all new bulbs were washed in distilled water , wiped dry with a clean cloth then wiped with ISO or Trike and not touched with bare skin again.
The water was to remove any salt residues from sweaty fingers , was told it could weaken the glass at running temps .
