Low Voltage Light bulb issues...

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jahilliard

Senior Member
We have installed a total of eight art lights. these are wall mount with (2)20w T3 G4 12v Halogen bulbs each. They come with a cord and plug in transformer that can be removed and be hard wired using individual transformers. These are 120V primary/12V secondary 75W transformers on each of eight fixtures. Alomost over night all but 2 bulbs burned out after a few weeks of being in place. We replaced all the bulbs and now the bulbs are out again after just a few weeks. The actual voltage coming from the transformers at the fixtures is 13V. Need some kind of idea of why these bulbs are burning out so fast. Any help would be great thanks.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
That's an 8% increase in voltage. I would get a trany that can be reduced in voltage-- some have tri taps on them. 120v bulb increased 8% brings it almost to 130V-- you wouldn't want that on a 120V bulb. I see it the same with 13V on a 12V bulb.
 

jahilliard

Senior Member
So you think that 1 volt could possibly be burning out the bulbs...is there possibly some kind of way to add resisitence after the switch that may be more affordable than 8 multi-tap transformers and removing and reinstalling X8? Not something I'm familiar with so I've got to at least ask for some money saving ideas for the customer.
 

Electric-Light

Senior Member
We have installed a total of eight art lights. these are wall mount with (2)20w T3 G4 12v Halogen bulbs each. They come with a cord and plug in transformer that can be removed and be hard wired using individual transformers. These are 120V primary/12V secondary 75W transformers on each of eight fixtures. Alomost over night all but 2 bulbs burned out after a few weeks of being in place. We replaced all the bulbs and now the bulbs are out again after just a few weeks. The actual voltage coming from the transformers at the fixtures is 13V. Need some kind of idea of why these bulbs are burning out so fast. Any help would be great thanks.
What's the voltage under load and what's the line voltage? What are the specs on the transformer?
Adding resistance is easy with 12v. You just increase the cord length and percentage drop quickly adds up on a 12v system, which is why car stereos require much, much larger wire than a comparable current and distance 240v run.
 
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TNBaer

Senior Member
Location
Oregon
When I sold lamps for a major international distributor low voltage lighting was my single largest complaint. MR16s, puck lights, T3 lamps and the rest of them were the source of endless misery for operations staff. Of course, architects and lighting designers love that stuff. Have you ever seen a 300 pound maintenance guy jam his big ole' mitts into a 3-inch can to try to replace a transformer for an MR16 that creates so much heat in such a small place that he has to do this task weekly? I have. The bulbs, even on a proper voltage, just don't seem to last.

My suggestion? Buy something else.
 

Electric-Light

Senior Member
Have you ever seen a 300 pound maintenance guy...
I know that ADA requires employer to provide reasonable accommodation, but I wonder if providing obese rated extra super duty ladder is one of 'em :lol::lol::lol::lol:

Many ladders are only rated 250 lbs. Some 300 lbs... but obesity extends beyond 300 lbs.

From the ADA site:
Reasonable accommodation is any change or adjustment to a job or work environment that permits a qualified applicant or employee with a disability to participate in the job application process, to perform the essential functions of a job, or to enjoy benefits and privileges of employment equal to those enjoyed by employees without disabilities. For example, reasonable accommodation may include:

* providing or modifying equipment or devices,
 

broadgage

Senior Member
Location
London, England
12 volt halogen lamps have a relatively short life, still shorter if over run.
1 volt is significant, as others post it is the same as running a 120 volt lamp on 130 volts.

Options include, reducing the effective voltage by means of a dimmer.
Use of extra long life lamps (these are 13 volts really, but by convention are called 12 volts)
Replace the transformers with ones with a 130 volt primary tap, or an 11 volt secondary tap.
Increase the length of the secondary wire in order to lose a volt by voltage drop, take care if doing this that the extra wire is spread out and not coiled or bunched up, as this could be a fire risk.
Or just accept it ! 12 volt halogen is very high maintenance.
 
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