# 12v 50watt halogen. amperage used?



## pimpin electrician (May 2, 2009)

Hey everyone.... 

Not too sure about this one, so I am hoping for some confrimation.

I am about to install (14) low voltage 50 watt halogen cans in a home.

I was figuring the total amperage was going to be just 5.8 amps. I thought they were going to be line voltage cans.

Today the lighting consultant informed me that they are going to be low voltage cans!

for my calculation do I still use the 120 volt line voltage number that is going to feed the cans, or the 12 volt output of the can for my calc number????

Let me know what you know... thanks!


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## pimpin electrician (May 2, 2009)

I am hoping that I do not have to add any new circuits for this..

I really don't think these cans will be drawing 58 amps!!


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## Switched (Dec 23, 2012)

Here, try this link. This will help you understand how to calculate it.

http://forums.mikeholt.com/showthread.php?t=136700


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## pimpin electrician (May 2, 2009)

Thanks Switched!!

I figured that since it is actually powered with 120 volts at the primary end, that it should be safe to just use the regular calculation.

Thanks a bunch!

happy wiring!

I don't really understand the advantage of even using these type of fixtures over the line voltage type? I'm sure they cost more, but why use them when you can get the exact type lamp and fixture style in line voltage?

oh well... to each is own..

is there any advantage in this case?


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## uconduit (Jun 6, 2012)

qty: 14, 12v 50watt; solve for I

solve for I
P=EI
(1/E)P=(1/E)EI
P/E=I
50/12=4.17

qty: 14; 12V, 50w, 4.17amps
14*4.17=58 amps

check my work:
700watts /58 amps = 12.07volts

does this seem weird? open your hood, look at your battery, read the cold cranking amps, look at your main fuse box by the battery, look at the high power car amps with their 4/0 and 750 kcmil wiring


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## uconduit (Jun 6, 2012)

120 volts at 5.8 amps === 12 volts at 58 amps (700w)

225000 volts at 2667 amps === 34.5kv at 17391 amps (600mw)

all you have to do is increase voltage and you can use thinner wires to transmit the same amount of power.


I have no idea why their is a benefit to 12volts for the home. The lower voltage lamps are more impact resistant, and the risk of electric shock/electrocution is practically eliminated


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## pimpin electrician (May 2, 2009)

UCONDUIT... you are now confusing me..

I am understand your calculations, and I did those myself before looking on here for further information.

I am almost positive that (1) 12 volt recessed can with a 50 watt halogen lamp is going to draw 4.1 amps from the 20 amp 120 volt circuit!!

Just doesn't seem right...

anyone back me up on this?


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## Vintage Sounds (Oct 23, 2009)

uconduit said:


> I have no idea why their is a benefit to 12volts for the home. The lower voltage lamps are more impact resistant, and the risk of electric shock/electrocution is practically eliminated


The quality of light they produce is nicer than line voltage equivalents, and the lamps tend to last longer partly because the magnetic transformer soft-starts them and partly because the filament is heavier and thicker but you could argue that Joe Homeowner isn't bright enough, pun intended, to be able to tell the difference anyway and in some installations where the lights are on for like 8-12 hours every day the MR16 socket has a way of ending up toasted and crumbly.


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## pimpin electrician (May 2, 2009)

the voltage used in cars are straight up 12 volts... so yes, bigger wire for the higher amps running through them...

In the case of these recessed cans which are powered by 120volt line voltage and then stepped down to 12 volts. I think the calc would be different my friend.


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## pimpin electrician (May 2, 2009)

True... the MR 16 for the low voltage cans have the bi-pin socket which always tends to burn up..

The line voltage cans have the same MR-16 lamp but with the G-32 base... or what ever it is.... better than the bi pin...


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## Vintage Sounds (Oct 23, 2009)

pimpin electrician said:


> UCONDUIT... you are now confusing me..
> 
> I am understand your calculations, and I did those myself before looking on here for further information.
> 
> ...


12v * 4.17A = 50.04w. You are talking about the current after the voltage is stepped down by the transformer.

if you put a 50w lamp in a light like this, you can probably expect about 5-8w in transformer losses. To be on the safe side estimate 60 watts per can. 

So, 60w/120v = 0.5A per light. With 14 lights that should be 7A.


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## pimpin electrician (May 2, 2009)

Thank you... I can rest now!!


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## Vintage Sounds (Oct 23, 2009)

Any time gangsta


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