low voltage drop problem

19 years ago

We had 12v linear undercabinet lights installed in our kitchen. Unfortunately, our contractor wired it so that there is one short arm with 4 10v lamps, and another long arm (25 feet) with 16 10 volt lamps. He put in a 300w electronic transformer in the basement. As you would guess, there is a significant voltage drop when all the bulbs are installed in the long arm. I really can't rewire with a thicker guage since the cabinets have blocked access to the walls. There also isn't much space to try to get the transformer closer to the first lamp. Would using either a "multi-tap" transformer or a DC transformer help to eliminate this problem? Thanks

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Comments (5)

bus_driver
19 years ago
Mention is made of 12V and 10V. Are the lamps 10 WATT? If not, what is the lamp wattage? That information is an important part of the situation.
harrymorton
Original Author
19 years ago
sorry, i meant 10 watt lamps
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bus_driver
19 years ago
So the load on the 300 watt transformer is 200 watts. I strongly suspect that the wiring is the problem- the gauge is too small. The longer string of lights is 160 watts, 13.3 amperes. The ampere load on a conductor is the cause of voltage drop. For 120 volts, 160 watts would be 1.3 amperes. A voltage drop of 2 volts, for example, is insignificant for 120 volts, but is a 16% drop for 12 volts. Lots of otherwise good electricians use small wire for low voltage. I suppose they have no experience with the older 6 volt systems on vehicles of the past. I use 18 gauge for door chimes, many use 24 gauge. Can you cut loose and abandon the old wire and run new in a more exposed location? #12 would be good as replacement.
harrymorton
Original Author
19 years ago
not really- the entire wall around it is now behind cabinets
bus_driver
19 years ago
Going back to your original question, using a higher WATTAGE transformer will not help. I also cannot recommend trying to send a higher VOLTAGE through those conductors to those 12 volt lamps. Those conductors are being heated by the voltage drop. Perhaps dangerously so. Obviously, to just stop using the lights is one option. That wall has another (back) side. Is it accessible? Often it is easier to access a wall cavity from "the other side". Can you open the wall below the cabinets? Can you open the wall above the cabinets? Can you change to a proper 24 volt system of lamps and transformer? That would cut the amperage in half and the voltage drop as a percentage of the system voltage would be just 25% of the present value.