LED 12vdc amps, consumption

[cptbeyond]

Im installing some LED strip light at my house as to become familiar with the install. A 16' strip draws 24 watts at 12vdc. According to PIE this is 2 amps. On a 15amp circuit one can power 180 watts 12vdc total. I understand according to PIE this is all that is allowed. Vs. Lighting on a 120vac circuit which allows for much more wattage. Im just finding this hard to believe considering LED lighting is to be far more efficient and energy saving. Does it truly consume 15amps quicker than 120vac lighting would? Am I to understand that if I was to power a 12vdc 30amp power supply i need to run 10gauge and protect with A 30amp breaker?

 

[iwire]

A 16' strip draws 24 watts at 12vdc. According to PIE this is 2 amps.

Yes

On a 15amp circuit one can power 180 watts 12vdc total.

More or less, that would be 15 amps and would not overload the circuit but voltage drop could be an issue.

I understand according to PIE this is all that is allowed. Vs. Lighting on a 120vac circuit which allows for much more wattage.

10 times as many watts on a 15 amp 12 volt circuit vs a 15 amp 120 volt circuit.

Im just finding this hard to believe considering LED lighting is to be far more efficient and energy saving.

Ohms law is not lying.

Watts is still watts and you are charged for watts not current.

Does it truly consume 15amps quicker than 120vac lighting would?

It really uses more current at 12 volts vs 120 volts, the watts remain the same.

Am I to understand that if I was to power a 12vdc 30amp power supply i need to run 10gauge and protect with A 30amp breaker?

Yes if that was allowed but low voltage lighting is limited to 25 amps per circuit.

 

[cptbeyond]

Yes if that was allowed but low voltage lighting is limited to 25 amps per circuit.[/QUOTE]

Low Voltage Lighting is limited to 25 amps per circuit? Is this a code? Thank you for your response

 

[augie47]

We just make this stuff up
No it IS CODE along with a number of other restrictions.
See Art 411

 

[iwire]

Low Voltage Lighting is limited to 25 amps per circuit? Is this a code? Thank you for your response

Sure is, which at 12 volts means no more than 300 watts per circuit.

I agree with Gus, take a few minutes to read article 411, it is short but has a lot of info you need to be aware of such as the wire types you can use.

If you conceal the wiring in the walls etc it will have to be done with line voltage type wiring.

Also keep in mind voltage drop is a huge issue, don't expect to run bare minimum sized conductors without having voltage drop problems.

 

[cptbeyond]

Great! Will take a look. Appreciate the input.

 

[jcassity]

thats a crap load of watts for that small of a strip!!

Remember, efficiency is in the eye of the beholder.

you gain in a possible infinate back up lighting time proportional to your qty of battery string size / AH run time.

you do lose at that voltage.

Right now as we speak i am engineering -48v LED tube lamps powered directly back to my customers dc plant.
These lights will supplement thier existing lighting and meet the max illumination they asked for.
They gain in that if the genset and / or utility fails, they can see!

These tube lights spec sheets (only two companies make them) say they draw about 150mA ea and are called 18W~something doesnt add up so thats why im setting up a test bench in my garage with a -48v rectifier
I was also told they are *NOT* polarity sensitive,, i will be doing come clamp on readings and also run the input voltage up to -60vdc and down to -40vdc and observe / document.

 

[iwire]

Right now as we speak i am engineering -48v LED tube lamps powered directly back to my customers dc plant.
These lights will supplement thier existing lighting and meet the max illumination they asked for.
They gain in that if the genset and / or utility fails, they can see!

If you are engineering them you will need to have them tested and listed if your customer is under the NEC.

 

[jcassity]

i am struggling with that very thing right now ,, i do need help with this if someone could guide me, been thinking of how to ask the question over at UL headquarters and such.
if you have advise,, 304 772 3411,, thats me.

im amazed at the fact that only one company i can find makes these -48v bulbs,, they do have all other voltages in AC & DC...

good prices to!!

 

[broadgage]

Regarding the code limit of 25 amp circuits for low voltage lighting, remember that the suppliers instructions also have to be followed, and that in the case of LED lighting strip these instructions will normally call for much smaller circuits.

The limit is often 2.5 amps, or 30 watts.

It would be usual to use a line powered LED driver for each length of LED strip, with an output limited to 2.5 amps at 12 volts.
A large number of these line powered LED drivers can be connected to the same 120 volt, 15 amp branch circuit.
AFAIK, a much larger 12 volt DC supply, up to the code limit of 25 amps, could be used provided that each length of LED strip was protected by a fuse or breaker not exceeding 2.5 amps.

The reason is that the conductors within the LED tape are very small and become dangerously heated at significant currents.

 

[James L]

Im installing some LED strip light at my house as to become familiar with the install. A 16' strip draws 24 watts at 12vdc. According to PIE this is 2 amps. On a 15amp circuit one can power 180 watts 12vdc total. I understand according to PIE this is all that is allowed. Vs. Lighting on a 120vac circuit which allows for much more wattage. Im just finding this hard to believe considering LED lighting is to be far more efficient and energy saving. Does it truly consume 15amps quicker than 120vac lighting would? Am I to understand that if I was to power a 12vdc 30amp power supply i need to run 10gauge and protect with A 30amp breaker?

I think what you're not taking into account is which side of the driver you're talking about - line vs. load
15 amps on the load side of your driver is not anywhere close to 15 amps at the breaker

Your driver (transformer) is changing the voltage on the load side, not the line side. 180 watts at 12 volts is 15 amps on the load side, but that same 180 watts at 120 volts is only 1.5 amps on the line side. The wiring to the driver is going to be whatever you're running for all your lighting (12 or 14 gauge). But the wire from the driver to the strips needs to be sized for the load at 12 volts

Just as important as the wattage load is voltage drop.

I have installed LED strip on numerous occasions, the most recently in a menu board at a fast food restaurant. I NEVER run a full strip in a single piece, because by the time you add cable length plus the length of the strip (16 feet), you have the potential for quite a bit of voltage drop at the end of the strip. I cut strips in half (8ft. long).

I would not install 7 or 8 strips off a single feed, either. If you run a circuit of only 35 ft., you would need a 2-guage wire to carry 360 watts (30 amps) with less than 3% voltage drop. Yes, a 2-gauge wire.

3% may not seem like much, but that's about 1/2 volt, which can adversely affect lighting performance.