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AssuredElectrical
AssuredElectrical, Master Electrician
Category: Electrical
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Experience:  Contractor-42+ Years in the ElectricalTrade
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Interesting question that I cant seem to find via Google search. Is

This answer was rated:

Interesting question that I can't seem to find via Google search.

Is it possible to use a standard 110vac lamp for a 12vdc light?

The plan would be to wire the 110vac lamp to 12vdc power, and then screw in a standard E27 base 12v LED bulb. The 12vdc power would come from a standard landscape lighting transformer.

Why I'm doing this? ... I'm installing outside lighting and have many more lamp options for 110vac 'outside wet location' lamps than if I look for 12vac landscape lighting lamps. The purpose of 12vdc power is for the ease of running direct burial cable, avoiding city permitting, etc.

It seems to me that the converted 110vac outside fixture should be able to power the 12vdc led lamp. But I just can't find any confirmation for that.

Please confirm and let me know what I should watch for in this conversion, or why I should not do it.

Thanks.

AssuredElectrical :

Welcome. My name is XXXXX XXXXX would be glad to assist.

Customer:

Hello Tommy.

AssuredElectrical :

hello

AssuredElectrical :

Read your information,

AssuredElectrical :

Most of the installations I do, I use a standard outside landscape fixture, rated at 120 volt and connect the low voltage. There is so much of a better selection as you have already noticed.

AssuredElectrical :

There is no problem doing this at all because the fixtures are rated for higher voltage than you are using, so all is fine

Customer:

OK, so I think you are confirming my belief then.

Customer:

But I have heard that led has polarity that needs to be adhered.

AssuredElectrical :

With the LED, you need to purchase Bulbs that have an INTERNAL resistor already inside

AssuredElectrical :

In other words, a bulb that is ready to go'

Customer:

Well, these are the bulbs that I can buy at normal retail outlets - correct?

AssuredElectrical :

Correct

Customer:

OK, so the most outside fixtures I see have standard e27 bases.

AssuredElectrical :

Yes and no, depends on the manufacturer.

AssuredElectrical :

I use E-27 and MR-16 personally depending on location and light level needed

Customer:

I'm thinking that I just need to buy a 12 volt, e27 base.

AssuredElectrical :

Good reflectors help to use the E-27

Customer:

12v e27 base.

AssuredElectrical :

Yes, correct

Customer:

ok good. I'll look up the mr-16.

Customer:

Just looking for something around 40-watt lumens equivalent in led. I like light around 3000 color.

AssuredElectrical :

I have some really bright MR16 LED's in my kitchen that really are amazing on light output.

AssuredElectrical :

Many manufacturers are misleading on their Lumens output, so be cautious and use a single trial before buying many of the bulbs

Customer:

So, once again (sorry), I am going to simply connect both wires from the transformer to EITHER of the 110vac wire leads which connect to the bulb base. The ground wire on the 110vac fixture is ignored. Correct?

AssuredElectrical :

Yes, the low voltage cable is only 2 wires.

Customer:

I can connect this way because an internal resister handles the polarity.

AssuredElectrical :

The white on your 120 volt fixture would be equal to the negative side of low voltage

Customer:

OK, I see the MR16 is 2-pin.

AssuredElectrical :

Correct and so is an E-27

AssuredElectrical :

the outside shell is negative

Customer:

But these have internal resisters also? Or would I have to pay attention to polarity with them?

AssuredElectrical :

The bulbs you buy will have the resistors built into them, so they are ready to go. Polarity is connect your white wire to the negative lead on the 120 volts fixtures

AssuredElectrical :

white negative, black positive

AssuredElectrical :

That way you are uniform

Customer:

OK, I can do that. Sorry I might have E27 wrong. For simplicity I was going to use a screw-in bulb. Thought that base was E27.

AssuredElectrical :

Be sure to use heavy gauge wire on the low voltage , they have calculators out for the distances and wattages to keep from getting voltage drops.

Customer:

Yes, I am studying the voltage charts.

AssuredElectrical :

Yes, E-27 is a screw in bulb. The shell is negative and the point on the end is positive

Customer:

The bulbs are ~120 feet from the transformer. But I am installing very few bulbs ...probably consuming less than 80 watts among all of them.

Customer:

I bought 12 gauge wire, and can buy heavier guage if needed.

Customer:

So far, the math I've done shows that 12 gauge is sufficient for such a low run.

AssuredElectrical :

Ok, still get a chart for wire length for the wattage to be safe and add for future

Customer:

low wattage run

AssuredElectrical :

Ok, great

Customer:

One of the information sheets I saw showed a 'closed loop' type of arrangement which was interesting.

AssuredElectrical :

Looping back to the transformer so if the cable is broken?

Customer:

No. Something to do with reducing voltage drop at the end.

Customer:

But ... my application is simple and over-engineered anyway. So I ignored the advice.

AssuredElectrical :

Yea, I just take time and get it all installed properly with no problems

Customer:

Tommy, you have been very helpful and I thank you for your clear and informative answers.

AssuredElectrical :

You are very welcome, glad to assist

Customer:

We're done - great job! Thank you.

AssuredElectrical :

thanks

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