Outdoor low voltage bulbs keep burning out

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Old 11-29-13, 09:51 PM
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Outdoor low voltage bulbs keep burning out

I recently installed a low voltage outdoor light system. I used a Malibu transformer that has an output of 120 watts. It transforms 120 VAC to 12 VAC. I have verified that this transformer has the necessary 12 volt output. I have installed two malibu lights to the system. I have also confirmed that each outlet fixture is receiving 12 VAC. In each fixture I installed MR16 lights that are rated 50 watts. The total wattage requirement is then 100 watts. The lights burn out within a matter of a day or two. When first turned on the lights are very bright and quickly become quite hot. I am thinking that the wattage on these bulbs is too high for my system and allow to much current through the bulb. This would explain why they become very bright and hot before burning out. I am thinking of replacing these bulbs with ones of lower wattage, say 25 watts. Any thoughts would be appreciated.

A related question is under what circumstances would a 50 watt bulb ever be used?

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Old 11-29-13, 10:18 PM
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I have installed two malibu light fixtures to the system... In each fixture I installed MR16 lights that are rated 50 watts.
What is the maximum wattage rating for the fixtures you installed? Are the bulbs you installed made to work on 12V DC?

The lights burn out within a matter of a day or two. When first turned on the lights are very bright and quickly become quite hot. I am thinking that the wattage on these bulbs is too high for my system and allow to much current through the bulb. This would explain why they become very bright and hot before burning out.
Overlamping will cause the fixture wiring to get very hot. It doesn't have any effect on the heat or the lumens generated by the light bulb.

I am thinking of replacing these bulbs with ones of lower wattage, say 25 watts
Sure, give it a shot.
 
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Old 11-29-13, 10:24 PM
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The bulbs are rated for 12 VDC and are being put into fixtures that are pushed into the ground. The instructions for the fixtures indicate that 50 watt bulbs can be used.
 
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Old 11-29-13, 10:35 PM
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I know the fixtures you are using. They got so hot the plastic lens melted.

Usually if you underload the transformer the voltage runs on the high side but 100 watts should have been ok.
 
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Old 11-30-13, 06:18 AM
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I would suggest measuring the voltage across the terminals at the transformer and the last light with all the lights on.
 
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