Low voltage fixtures

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Old 12-11-08, 02:42 PM
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Question Low voltage fixtures

I am replacing existing exterior light system with a low voltage system. I have been doing electrical work all my life but this is the first time dealing with low voltage. Not a problem but the customer wants to put regular exterior lights back not low voltage. His argument is that if it is designed for 110 then why wouldn't it work on 12. I see his point but am sure I will regret doing it., ,Please advise.


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Old 12-11-08, 02:51 PM
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Can you provide us with details? Is the low voltage wiring only from the fixtures to the their power source?
 
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Old 12-11-08, 02:57 PM
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Originally Posted by bbwolf5 View Post
His argument is that if it is designed for 110 then why wouldn't it work on 12. I see his point but am sure I will regret doing it., ,Please advise.
The flaw in his argument is that when voltage drops, current increases to power equivalent wattage lamps.

Watts = Amps * Voltage

When watts are held constant, you drop the voltage by 10x, the current increases by 10x which your existing wiring may not be able to handle. The other major complication is that higher voltage can travel longer distances, so if you have a large system you may have trouble with too high of current and too much voltage drop if the wire runs are long.

Example: You have 500W of lights on a 15A circuit using #14 wires. This means 500W / 120V = 4.16A of current. Drop the voltage to 12V: 500W / 12V = 41.6A current which far exceeds the 15A ampacity of your #14 wire.
 
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Old 12-11-08, 03:22 PM
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Originally Posted by thinman View Post
Can you provide us with details? Is the low voltage wiring only from the fixtures to the their power source?
Yes the transformer is about 60' away and am running the low voltage wire to fixtures that are not low voltage fixtures. 8 in all. Sounds like it is a no go.
 
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Old 12-11-08, 03:31 PM
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Originally Posted by bbwolf5 View Post
Yes the transformer is about 60' away and am running the low voltage wire to fixtures that are not low voltage fixtures. 8 in all. Sounds like it is a no go.
That is a correct statement. Explain to your customer that 12 volt wiring is not rated for use with 120 volt lights.
 
 

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