I have a friend who moved into a house with a "fiber optic" pool light
unit that wasn't working when he moved in. He went to the pool store
and they gave him a replacement bulb -- it's a GE 24V 250W halogen
lamp, i think its the same as this one:
anyway -- the thing starts working but only lasts a couple of hours
and burns out (the lamp is visibly grey on inside of bulb).
The one thing odd i noticed is that the open circuit voltage of the
transformer is only 20V.
Possibilities? I'm thinking the open circuit voltage for a 24V light
would be way above 24v(?)... Is it possible it's really a 12V system?
Any other ideas? what else would cause the bulb to pop?
These bulbs are pricey (~ $20) so I don't want to just keep popping
[halogen bulbs run better hot -- something about the tungsten atoms
redepositing on the filament with high heat]
It sounds as though it could be a heat problem. Is the unit well
ventilated? Are there any dirty filters? A defective lamp socket or loose
connection can cause excessive heat on the filament. Look for signs of
burning or arcing on the lamp socket and the wiring that feeds it.
Are you sure that the proper bulb for the unit was installed?
It may be a 20 volt power supply to make the bulb last longer. Look around
on the nameplate or inside to see if it mentions output voltage anywhere.
250 watts in a little MR-16 bulb is a lot of heat. That bulb is rated for
50 hours at 24 volts and is to be used with the socket base down or up only
to full horizontal. The lamp socket should never be higher than the
A bulb run at less voltage will last longer , almost indefinatly at 5%
-10% rated voltage. You have other problems, moisture hitting bulb, oil
on bulb , a bad bulb , bad socket causing arching or overheating.
Do not touch the bulb with your fingers. Use a clean gloves or rags. The
oils on your hands cause them to burn out so soon. If you touch the lamp
clean it with alcohol and let dry before installation. Read the directions
with the lamp most say do not touch the lamp.
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