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Old 08-29-2007, 11:19 AM   #1
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Calculating Amps draw for low voltage


Hi people! This is an awesome forum!

I'd like to install recessed lights with low voltage. I just picked up a Lightolier 303MRE ultra shallow fixture:

http://lightolier.com/index.jsp?CATR...54&B=363&C=365

I really like the low-profile feature.

My question is to determine how many amps this fixture draws, do I divide by 12V or 120V? I know the fixture is rated at 37W. Thank you for any help.

Suprashy

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Old 08-29-2007, 11:40 AM   #2
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Calculating Amps draw for low voltage


Just got this extremely speedy info. from Lightolier:

<<Model Number:303MRE has an electronic Xformer made by Lightech LET-75 max
for Xformer is 75w and fixture is being supplied 120V their for 75w/120v =
.625 Amps>>

Which is awesome news bec. the amp draw is very low.

Suprashy

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Old 08-29-2007, 06:04 PM   #3
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Calculating Amps draw for low voltage


It depends if you want the amp draw on the 120 volt source or the amp draw on the 12 volt light side. The light will draw 10 times the amps as the source.

Last edited by joed; 09-10-2007 at 06:27 PM.
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Old 09-10-2007, 09:33 AM   #4
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Calculating Amps draw for low voltage


37 Watts being drawn at 12volts = a current draw of 3 Amps. This means that 3 Amp will be running through your 'fixture'.

By the way, it is a myth that low voltage lighting saves energy costs. Usually the compact transformers (not electronic) are made in China & are poorly made. In general, a 100 Watt wire wound compact transformer is used to supply a 12v 50 Watt halogen downlight. At least 50% of the energy used by the transformer is given off as heat. In effect, you pay for 100 Watts of electricity to use a 50 Watt light...very expensive.

This is a different matter with 'electronic transformers'.
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Old 09-10-2007, 06:30 PM   #5
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Calculating Amps draw for low voltage


I agree low voltage light does not save you any money. However, a 100 watt transformer does not draw 100 watts all the time. That is only the maximum it can supply. It has some losses do to efficiency but I doubt very much that is is only 50% efficient.
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Old 09-10-2007, 07:51 PM   #6
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Calculating Amps draw for low voltage


Quote:
Originally Posted by joed View Post
I agree low voltage light does not save you any money. However, a 100 watt transformer does not draw 100 watts all the time. That is only the maximum it can supply. It has some losses do to efficiency but I doubt very much that is is only 50% efficient.
With these particular transformers, it is the case. This is the main reason why people are changing to the electronic type.
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Old 09-16-2007, 04:37 PM   #7
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Calculating Amps draw for low voltage


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Originally Posted by elkangorito View Post
With these particular transformers, it is the case. This is the main reason why people are changing to the electronic type.
I just found a weblink that may be of some interest. Please note that it is stated that the older inductive type transformers use 10% to 30% more energy than the actual lamp. I stated 50% because generally, the efficiency is relative to the amount of money you spend on each of these type of transformers. Still, it's much better to use the electronic type.

http://www.greenhouse.gov.au/yourhom...nical/fs45.htm

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