Calculating load of low-voltage lights

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Old 12-02-07, 04:49 PM
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Calculating load of low-voltage lights

I have a 12v 300W transformer for use with my low voltage lighting. If I max-out the transformer w/ 15 x 20w 12v lamps is the wattage pull on the 120v side the 300 watts and will thus use 2.5A?

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Old 12-02-07, 05:03 PM
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More or less, yes. You are neglecting the transformer losses, but if you're cutting it that close then you have other issues. I'd figure this as 3A.
 
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Old 12-02-07, 05:07 PM
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Originally Posted by DavidT View Post
I have a 12v 300W transformer for use with my low voltage lighting. If I max-out the transformer w/ 15 x 20w 12v lamps is the wattage pull on the 120v side the 300 watts and will thus use 2.5A?

Thanks.
The primary side have no affect with this but secondary side it will because the NEC code useally maxed the secondary side to 300 watt on low voltage lighting circuit and that will come up to 25 amp max [ 300 watts ] and with max rating you may have some voltage issue with it and also the wire size as well.

the low voltage lighting system is very senstive with voltage drop if not done in proper way.

noramally #12 wire is limited to 20 amp so you only can use 240 watts [ low voltage side]
and with #10 will help only if invold some distance with it.

Merci, Marc
 
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Old 12-02-07, 07:50 PM
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Although not the reason for my original reply, for the record I'd ordered 12 awg, I believe on advice of the vendor. If it doesn't work, I guess I'll have to replace it.

Thanks for your advice.
 
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