? about low-voltage lighting wiring

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Got a client with an outdoor low-voltage lighting system in need of repair. Basically just 7 surface-mount lights on a stairway outside.
It's currently wired with some kind of zip cord, which may or may not be the right stuff. (Looks like 12-14 ga.) Here's what I'm proposing to do:
Tear out most or all of the existing wiring, which is partially buried, partially above ground. Using the existing fixtures where possible (see below), rewire using new wire of the correct type, burying cable as needed.
What I'm not sure about is the following:
1. Correct type of cable to use: Checked at Home Despot, which sells something identified as "landscape lighting cable" in the form of 2-conductor zip cord, black, in several gauges. I'll probably use 12, as the run is less than 200' total, and voltage drop isn't currently an issue (when the system was working, all lights were equally bright).
Is this stuff OK to use outside? Two issues I can think of: buriabilty and resistance to sunlight. Parts of the existing wiring have deteriorated to the point of shorting out.
I understand from some online sources (like this one: http://www.iaei.org/magazine/?p"90) that what I should be looking for is type SPT-3 cable. Is that right? According to this article, it needs to be buried 6" (except under driveways and such, which isn't an issue here).
I realize I could use UF for this project, but that would be more difficult for several reasons, and much more expensive (UF is about twice the cost of the zip cord for the same gauge). So I think I want to stick with the zip-cord stuff. With UF, I'd either have to use junction boxes at each light, or figure out some Rube Goldberg way of connecting the lamps to the UF.
2. Connections: The replacement lights I've looked at all have what I consider to be cheesy connectors on them, the type that stab into the cable and pierce the insulation. Not much better than those quick plugs that squeeze down on the cord and pierce it.
So I'm planning on going either with wire-nut connections or soldered connections. I'm thinking that soldering, which probably the best solution, is probably overkill, and makes later maintenance more difficult. So it seems to me that a good wire-nutted connection, wrapped in lots of electrical tape to keep out moisture, would be acceptable.
3. Light fixtures: Currently the fixtures are those little round surface-mount ones that take a 7-watt halogen bulb, made of plastic. These appear to be all that's available today, at least easily: on a recent grueling research trip I visited both Orchard and Home Despot, which both have those Malibu units. Home Despot wins here because they also have these in metal instead of plastic. However, the metal ones aren't really much better, because in all of these fixtures, the weak point is the lamp socket, which appears to be identical in all types, just a simple push-in type of socket.
If anyone knows of better fixtures (that don't cost an arm and a leg), I'd appreciate knowing of them. These ones can be had for about $12 for the metal ones.
And no, the homeowners don't want different lights, like those upward-pointing ones or ones on stakes on the ground.
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The low voltage stuff is designed to work with an oversized zip cord. That is all it needs.
Dim lights can be caused by corroded contact where the wire is bitten.
A 200 foot run sounds a little long for most of those units.
--
Colbyt
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On 7/25/2010 2:56 PM Colbyt spake thus:

Well, OK, but what about burying it? exposure to sunlight?

Problem is not dim lights. But that's just more confirmation why I don't like those cheesy connectors that come with the LV fixtures.

I said the run was less than 200'; I just mentioned that because the page I referred to (http://www.iaei.org/magazine/?p"90) said that "12 AWG is recommended for runs up to 200 feet". So I should be fine with 12 ga.
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Never had any problems over 10 years with either. Burying the cheap clamp connectors can lead to problems much sooner.
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If you object to the cheesy connectors, go out and buy REAL connectors like Scotchlok IDC connectors which seal the connection with a sealant when you crimp the connection...
A real electrical supply house is where you would have to go to find "real" electrical supplies...
~~ Evan
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On 7/25/2010 3:55 PM Evan spake thus:

So how would you rate these compared to wire nuts and solder plus electrical tape?

I'm quite aware of this. I go to HD because it's close to me and (sometimes) cheaper. But the real supply house ('round heah it's Emperor Electric Supply in downtown Oakland, a Chinese-owned business) is the place to go.
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Well, you wouldn't be using wire nuts AND solder... So which connection method did you have in mind ?
Wire nuts and tape will eventually leak unless they are protected within an enclosure... Soldering every connection is overkill...
You complained about the cheesy IDC connectors included with the lighting kits, my recommendation is to seek out more expensive IDC connectors which seal the connection with a sealant which has been tested for use with electrical devices...
~~ Evan
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now you only have 49 watts of lights, but if in the future more or stronger lights are added, you might have some visible differences. These can be avoided by connecting both ends of the wire to the transformer terminals, making a continuous loop. New timers/transformers should have more detailed instructions on this in their information sheets.
There is also a lot of information at http://www.residential-landscape-lighting-design.com /, which also covers the loop method.
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David Nebenzahl wrote:

On the other hand, how long has this "crappy" configuration worked without a problem?
If more than five years or so, I'd just duplicate it. Maybe seal the contacts with Silicone.caulk.
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wrote:

Yes. Skin the wires past corrosion. Wire cap it and fill the cap with silicone. No moisture in the connection.
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David Nebenzahl wrote:

I don't know with modern day zip cord, but some old stuff was good in uv light and some was really bad (florescent lights inside) . Working on old/antique juke boxes the one brand "AMI" was always known for the insulation almost falling off the wires. Other brands the same age and similar lights were just fine.
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The black 12ga cord is what they all use. It's fine. The stab connectors are ok for a while but do eventually corrode. Moving them to another spot on the wire fixes that. A better connection would last longer but is more work. Don't bury the connections if at all possible. Most of the light fixtures have a way to loop the cord inside the fixture so you do no thave to bury the connection.
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While we are on this subject, is there such a thing as high-quality low voltage outdoor lighting ??? The stuff at the big box stores is SO cheap, and the bulb sockets are so crude, always causing problems over time....
thanks !!
James
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wrote:

Short answer is NO.
Honestly I didn't check on what QVC is touting.
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"> While we are on this subject, is there such a thing as high-quality low

*Check out Kichler and also Hadco. I recently installed a bunch of Kichler lights around some steps. I was very impressed with the durability. Of course they listed for around $300.00 for each fixture.
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With that price you can install a complete new cheap set every 5 years for the next 30 years. Hadco still has a "quick connector". Is that a crimp on that breaks the insulation? Cause that's the same thing the cheap ones have and the problem is long term they corrode.
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John Grabowski wrote:

At that price I think I'd run 120VAC and forget the low voltage stuff.
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Good point. 120 is far less affected by connection resistance than low voltage. The main problem I find with all the outdoor low voltage stuff is long term the connections and the bulb sockets develop tarnish or corrosion.
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Home Depot has some good high quality 12v fixtures. I did a 250' driveway with 12 fixtures. List price on the fixture was $120/ea, HD had them for 1/2 that and ran a sale for a while for less than $30.
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I like bayonet. I put marine grease on the bayonet bulbs in my motorcycle. That solves the corrosion issues. I thiink you can use other greases as well, just that I have marine grease around for the boat. I think the base of the wedge ones would get too hot to do this.
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