120v vs 12v outdoor lighting

[stmlandplan]

We have a street frontage (900 lf) where we are trying to light a pathway using downlights from trees spaced 40' O.C. as well as uplighting them. My total fixture count is (22) Downlights mounted at 12' in addition to another (46) uplights. I am concerned about the long frontage and trying to do this with multiple transformers and photo sensors. The wattage of the 12v LED downlights is 13w and the uplights are 5.5w for a total of 540w. Given the long distance and the total load should I be looking at 120v rather than 12v?

The first attachment shows the entire frontage and the second a zoom in of the lighting plan.

 

[ruxton.stanislaw]

Low voltage lighting, especially in common areas and outdoors, is always going to be much better for safety and liability.

There are a couple solutions that come to mind here. The most simple is probably to run a few separate 120 - 12v transformers to reduce the length and load of the low voltage strings, like you mentioned, and control that entire circuit with a single photo sensor.

One other option could be to use a center tapped 24v transformer with additional conductor or more ideally, three phase (three regular 12 volt transformers wired for such) if the LED drivers accept AC current and that is available to you. That gets you down from 45A to 22.5A (center tapped transformer) or 15A (three phase wye) on each conductor respectively. The requirement would be more conductors for the length of the complete string, but a much smaller wire size that is easier to work with.

DC-DC converters can also come in handy to regulate voltage or still stay within the low voltage safety margins (e.g. 48 - 12v DC).

 

[stmlandplan]

Thanks so much for the reply ruxton.stanislaw. I see 3 conductors atop the adjacent line so I have to believe that we could get 3-phase with no problem. Not being an electrician or electrical engineer, I am unclear how I would need to write the specifications for a bidder to know what they are bidding. Care to elaborate with this in mind? The products I had selected for use are shown below. I was planning on using a Vista Pro Lighting transformer (or equal).

 

[mhanson]

Just an observation, The Model 3106 appears to be a "UP Light". Double check, But I don't believe this fixture is suitable for pointing down.
It usually has to do with drain holes in the fixture.
Good Luck

 

[stmlandplan]

good point. Thanks, I will verify.

 

[Fred B]

Not being an electrician or electrical engineer

Spec out the number of lights and spacing and what your desired outcome or look would be and leave it to the Electrical professional to how best to get it done.

 

[stmlandplan]

Great recommendation Fred B! ...I actually got to that point yesterday and forwarded our design intent to an Electrical Engineer to review and develop the best plan for implementing it.

 

[PaulMmn]

Where possible, feed each segment of a run from the center, not the end... voltage drop is cut in half at the 2 ends.

 

[Mystic Pools]

Great recommendation Fred B! ...I actually got to that point yesterday and forwarded our design intent to an Electrical Engineer to review and develop the best plan for implementing it.

That's a good move.
I have some experience over the years where my projects will have landscape lighting. Usually my landscape contractor handles that. Power is provided where needed for transformers.

But I'll bet Vista has tech/design department that will take your plan and design/spec accordingly. Especially if you will be using their products.