Tree Light Work Around

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infinity

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I have a row of trees along the driveway that have permanent 12 VAC tree lights shining up illuminating the trees. How can those tree lights be disconnected and be temporarily converted to provided 120 volt for Christmas lights in the trees? Disregarding any code issues would a 12 to 120 volt transformer at each tree actually work?
 
If the existing lights are halogen, and the new are led, you will probably have enough power, but if existing are LED, the transformer may be too small. You would just have to do a load calc. Also use an electronic converter instead of a magnetic transformer, inrush might be too great.
 
hillbilly1 said:
If the existing lights are halogen, and the new are led, you will probably have enough power, but if existing are LED, the transformer may be too small. You would just have to do a load calc. Also use an electronic converter instead of a magnetic transformer, inrush might be too great.
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The existing transformer output is 300 watts @ 12 volts. The total load is about 60 watts with about 1/2 of that being removed when the 120 volt lights are installed.
 
I think cheap door bell transformers are 16vac 10va. Give you about 90 vac usable at each tree. A whole string of C9 LEDs 25 lights is like 5 watts
 
As long as the cost is the same, or less, than transformer conversion - they do make 12v led string lights LINK that wire to existing 12v supply (without requiring 120v to 12v dongle).
 
TwistLock said:
As long as the cost is the same, or less, than transformer conversion - they do make 12v led string lights LINK that wire to existing 12v supply (without requiring 120v to 12v dongle).
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That might be an option but those are pretty expensive when compared to the 120 volt sets. You wold have to weigh the cost of adding some type of transformer at each tree. Lowe's has 100 light LED sets on sale for $5.98 each. I'm guessing that these trees would require at least 800-1000 lights per tree.
 
Stepping 120V down to 12V and then back up to 120V will work, but you won't have much power available at 120V. You currently have 60W of total lighting load, and due to voltage drop and such I wouldn't want to increase that much.

With that said, LED holiday strings don't use much power; this 150 lamp set uses 9W :
You don't know the power factor or THD of these 9W strings, so you don't know the transformer VA needed. But I'd think something in the 20-30VA would work.

IMHO it will be hard to beat the 12V light strings that @TwistLock identified. They are a bit spendy compared to 120V light strings, but you don't need to pay for the transformer and figure out how to waterproof it. You also aren't in trouble if it turns out your 12V 'transformer' is actually a power supply that provides 12V DC.

-Jonathan
 
winnie said:
... IMHO it will be hard to beat the 12V light strings that @TwistLock identified. They are a bit spendy compared to 120V light strings, but you don't need to pay for the transformer and figure out how to waterproof it. You also aren't in trouble if it turns out your 12V 'transformer' is actually a power supply that provides 12V DC.

-Jonathan
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And even if it's an "electronic" transformer with an AC output, it may not be happy with the inductive load from transformers. Such a load could even cause output transistors to fail from transient overvoltages.
 
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