landscape wiring

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  #1  
Old 04-18-14, 06:57 AM
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landscape wiring

I am getting my driveway redone and I want to install some 24V low voltage lights on the retaining walls and path leading to the house. But I can't afford to do it now, so I just want to lay out the groundwork so I can do it later. It'll be really simple, maybe 3 lights on each side of the driveway in the retaining walls. And 3 lights on each side of the path. The path lights would ideally be in the pavers.

My questions are:
1. I need to use pvc to hold the cables correct? What size?
2. What kind of wire do I need and how much. I am guessing 16/2 for each side. So 4 in total. 1 on each side of the walls and 1 on each side of the path.
3. Where do I place the pvc? I can assume I need to run it to the head of each retaining wall and the head of the pathway. But do I need to run it the length of the walls and path? I guess I should just to protect the wires.
4. To connect the lights. I would cut the 16/2 cable at each light and splice it to the light?
5. When connecting the wires to the lights. I would make a hole in pvc right? So the wiring would be exposed to the soil and gravel at that point? And water/dirt could get into the pvc. Is that okay? I guess this relates to question #3.
6. Whats a quality brand to use for the lights?

Any others tips would be great.
 
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  #2  
Old 04-18-14, 07:33 AM
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For this low voltage application, you can use direct burial Romex (I think the technical term is UF) with no depth requirements and no conduit. I think you would need at least 14 gauge, possibly 12 gauge depending on the wattage of the lights and length of the run. I don't have the numbers handy but in terms of voltage drop you do not want to lose more than 1-1/2 volts (6%) at the farthest light compared with the nearest since more than that and you will see a noticeable difference in brightness among the lights.

The calculations can be more complex although not that much more difficult given that you may have something like 10 amps between light 1 and light 2, 8 amps between light 2 and light 3, 6 amps between etc. compared with one calculation for the entire run that may produce a larger wire size.

Wires in buried conduit, no matter how well the conduit is sealed, must be wet rated, for example THWN and not THHN.

It is better to bring the wires up to the surface, perhaps into each fixture, to make connections and splices.
 
  #3  
Old 04-18-14, 08:21 AM
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I think I need to use a conduit because some of the run is going underneath an asphalt driveway. So I will never be able to dig that out once the driveway is paved. Does that make sense?

Doing some more research I read that if using the conduit, then I need to run individual THWN wires. So I am currently thinking, I'll run 1" PVC throughtout and put 8 pairs of 12 AWG wires. Each wire should be a different color correct?

Heres a rough sketch of my project. Name:  pvc.jpg
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Like I said, this isn't set in stone, so I want to lay the groundwork with the most versatility do when I do get this done, everythign will be easy.
 
  #4  
Old 04-18-14, 08:25 AM
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Use schedule 80 PVC or IMC under the driveway.
 
  #5  
Old 04-18-14, 11:30 AM
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I found some lights and realized 12v LED is the more common standard (not 24). They also come with 18/2 connectors. I guess that makes sense, since the LED light is about 13 watts and so the current is 13/12 or about 1 amp. If I put 3 lights on one run, that is 3 amps?

So am I over doing it by running 12/2? I guess 12/2 is more future proof. But it seems like overkill.

Also, how deep should the pvc be under the ground?
 
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