Low Voltage Landscape Qs

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Old 06-22-09, 06:00 PM
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Low Voltage Landscape Qs

I'm a novice Elelctric DIY'er and am looking at putting in some low voltage landscape lighting. A few questions:

- i'm thinking the same basic principals apply in that i can splice different runs of wire together? Or does this stuff have to be wired in seqence? i was hoping to design a few different runs out fro mone main "junction" box.

- just add up the wattage of the fixtures, multiply by somethign like 80%, and that tells me the wattage of the transformer needed?

- anything with length of the run of wire that might affect the performance? like a voltage drop or anything?


thats all i can think of now -- couldnt find these q's online here.
 
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Old 06-22-09, 06:58 PM
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Originally Posted by bheron View Post
- i'm thinking the same basic principals apply in that i can splice different runs of wire together? Or does this stuff have to be wired in seqence? i was hoping to design a few different runs out fro mone main "junction" box.
I suggest running a "feeder" off the transformer and then tap off that for each light. Most low voltage kits come with a running tap just for such purpose or you can buy them separately. Low voltage lighting does not require splices to be in a box. Just use connectors rated for outside.


Originally Posted by bheron View Post
- just add up the wattage of the fixtures, multiply by somethign like 80%, and that tells me the wattage of the transformer needed?
No need for 80%. Just add up the max watts of the fixtures and choose a transformer to handle at least that much. I suggest getting an over sized one unless your sure you will never add any more.


Originally Posted by bheron View Post
- anything with length of the run of wire that might affect the performance? like a voltage drop or anything?
Low voltage is more susceptible to voltage drop. If your doing a long run you will just need to up the size of the main feeder wire (cable)
 
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Old 06-22-09, 07:02 PM
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thanks for the feedback. the reason I was asking about running splices is that i dont want to do one long single line of wire. im thinking i can use much less wire if i connect multiple runs together?
 
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Old 06-22-09, 08:33 PM
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I agree with multiplying the total light load by 80% to rate the power supply. Generally accepted practice for low voltage installations of any kind is to allow for 20% headroom on the power supply. If your lights total 200 watts, opt for a 240-watt transformer. It will run cooler and allow for some additions in the future.

You also have the right idea to keep the wiring runs short. They don't have to daisy-chain from one light to the next. They can all home run, or you can run several "feeders" to each power a few lights.

Voltage drop is a major consideration. All of the landscape manufacturers have calculators on their websites, and the packages of landscape cabling that are available at the big box stores have charts on the packages.
 
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Old 06-23-09, 01:32 AM
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The other thing let me add in here which I deal with them from time to time majorty of the Low Voltage transfomer must be outdoor per manufacter instruction.

As far for other question all the guys hit right on the spot with their answer.

As you may noticed some of the Low Voltage transfomer do have multi tap on secondary side so you can able finetune the luminarie brightness depending on the type of cable / conductor size that is very impoart to remember that.

Merci,Marc
 
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Old 06-23-09, 08:20 AM
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Originally Posted by bheron View Post
i'm thinking the same basic principals apply in that i can splice different runs of wire together?
Yes, your lighting vendor will sell tap and splice kits which essentially just snap onto the two wires to allow you to extend it in any direction.

- just add up the wattage of the fixtures, multiply by somethign like 80%, and that tells me the wattage of the transformer needed?
Add up the wattages of the lamps and multiply by something like 120% -- 100W of lamps would need a 120W transformer or larger.

- anything with length of the run of wire that might affect the performance? like a voltage drop or anything?
Yes, low voltage is very sensitive to long distances. Your lighting vendor should publish a chart which tells you what size wire to use for the distance and the watts. If you skimp on wire size, the lights at the end of the run will be noticeably dimmer than the ones at the beginning.
 
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Old 06-23-09, 09:45 AM
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ok, this is really good info. im looking at home depot and amazon.com and havent seen anything tap and splice kits. Both places I'm looking at malibu lighting. the only thing I noticed in their directions was that the first receptacle had to be 10 feet or more from the box.

this is good to know b/c I have a fairly large area - am thinking I may need over 400W. Right now I have 1 run of 100' of 12 gague wire. I'd rather have a bunch of short runs coming from the transformer.
 
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Old 06-23-09, 10:58 AM
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UPDATE: from the Malibu Lights website FAQ, some good stuff:

Wattage Range and Wire Guage
217-300 watts - 12 Guage
157-216 watts - 14 Guage
121-156 watts - 16 Guage
0-120 watts - 18 Guage


- They dont mention the 400-600 watts range. I've purchased 12 guage so far.


"Can more than one run be attached to my power pack?" Yes, only two seperate runs are recommended. Both runs attach under A and B terminals and may not exceed the total power pack wattage rating.
- Im guessing the larger packs have more than one terminal set.


"Is there a postitive or negative in the wires or cable?"
There is no polarity in the wires or cable unless you loop it to the transformer wich is not necessary.


And then, just as everyone has said on here:

"What is the maximum length of cable I can attach to my transformer?"

There is no maximum cable lenght, however, longer runs of cable can result in lower light output near the end of the cable. Therefore, you should use heavier cable or shorter runs to ensure maximum light output. Most important, you must never use cable that is smaller than that listed in the table for your transformer.


So, nothing on tap/splice kits but I have no problem with splicing the wires and using caps to secure the twists of 12 guage wire. Looks like I have a single run form the transformer spliced out to a coupld of smaller runs to minimize the total amount of wire used.
 
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Old 06-23-09, 12:03 PM
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You shouldn't run more than 300W through a single length of wire. Split it such that no more than 300W is on each leg.

The bigger transformers usually have two or three sets of terminals capable of supplying about 300W each. Pick out a specific transformer and download the instruction manual PDF. It will have more detailed information about the terminals and wiring sizes particular to that unit.

For example, Malibu 600W transformer description on Amazon:
Product Description
...600W, Power Pack With Timer, Contains Two 300W Circuits, 2 Sets Of Trip...


I thought Malibu sold splice kits, but it looks like they recommend soldering splices instead. That makes sense as mechanical connections aren't that reliable underground. Solder and heavy duty tape will probably make the best connection. Don't use wirenuts (caps) as they will not hold up underground. At the very least use automotive style crimp connectors.
 
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Old 06-23-09, 05:33 PM
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Originally Posted by ibpooks View Post
I thought Malibu sold splice kits, but it looks like they recommend soldering splices instead. That makes sense as mechanical connections aren't that reliable underground. Solder and heavy duty tape will probably make the best connection. Don't use wirenuts (caps) as they will not hold up underground. At the very least use automotive style crimp connectors.
I agree with the crimp on connector assessment. Although I have used them and they worked fine, I don't know how long they would last being in the ground. I have used wire nuts listed for underground ( IDEAL INDUSTRIES, INC. - UnderGround Twist-on Wire Connector ) which have worked well. I would personally use them before automotive crimp connectors in the ground.
 
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Old 06-24-09, 05:06 AM
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Solder and shrink-tube is the best way to do it. If you use wirenuts, butt-spice, or other mechanical connectors, seal the splices with silicone caulk.
 
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Old 06-26-09, 06:44 AM
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ok, i'll try some of those approaches for connecting the wires. will have to look up the automotive crimp connectors and see what they are.

ipbooks - i'll look for a PDF manual for the transformer. the only thing i was able to find on malibu's website was the same skimpy instructions I found in the box in the store.
 
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