Blowing It On LV Landscape Lighting

Nailbird

Folks,

Okay, I'm learning that low voltage landscape lighting isn't so easy.

I've installed pathway lighting and am having trouble with blown bulbs. The path involves 12 fixtures, each fixtures uses a 12v 20w MR-11 halogen bulb. I'm using 2 circuits wired with 12-2 with 6 fixtures each; the first circuit is 50 feet long with the fixtures distributed equally along its length, the second circuit is 100 feet long with the wire running past the first circuit then picking up the same spacing of the fixtures. Each circuit has a dedicated 12vac electronic transformer rated at 30-150 watts; the bulbs are rated 12v AC/DC. I'm using AC transformers to avoid voltage drop issues associated with DC circuitry, and when the bulbs are working they all seem equally bright. The transformers are mounted in a plastic electrical box in the crawlspace with wires running out to the garden path. Nothing seems to be overheating.

I installed everything, connected up the light switch, and voila - a beautifully illiuminated path... for a few hours. Later that night I noticed a couple of lights were out; some infant mortality on the bulbs I figured. So I replaced them and the next night everything worked fine... but at the end of the night I'd lost 6 bulbs.

Clearly I'm doing something wrong! HELP!!

Cheers,
TY

Tiger

What is the voltage at the fixtures?

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www.TigerElectrical.com

Nailbird

A little over 12v - that was my first thought too. I'm using a good quality MR-11 bulb and they're rated AC or DC. I'm stumped.

ampman

framers should not do wiring electricians can do any thing

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an army of sheep lead by a lion will defeat an army of lions lead by a sheep

willworkforbeer

Do a little electricity 101. Dont be clueless.

Nailbird

Hey 'ampman' and 'willworkforbeer' - thank God you're working with electrons because neurons are definitely in short supply! If you don't have something productive to say STFU.

ampman

what do you expect you are a framer with a simple low volt question ,stick to your trade unless you cant make it as a framer

__________________
an army of sheep lead by a lion will defeat an army of lions lead by a sheep

willworkforbeer

Framers...

Tinstaafl

Who died and made you boss o' the board? You're in a construction zone, guy; grow some skin.

I'm not a low voltage guy per se, but I do have an electronics background. I've encountered similar early failure when running AC to lamps intended for DC. My solution was to slap a couple of diodes in with a center-tapped xformer and a cap to provide DC instead. You could even series a resistor to drop the voltage a bit for even longer life.

Or simply use transformers with a lower output voltage. Sometimes the specs on lamps like that are less than optimal.

Nailbird

Tinstaafl - it sounds like you suspect it's a frequency problem with the electronics of the AC-AC transformers? I checked the specs of the bulb manufacturer, Higuchi, and they are rated for AC. I'm running an interior setup in a media room with the same transformers and bulbs and it's working flawlessly; the only difference is the length of the run and the fact they are outside. But I'm not having a voltage drop issue...

Tinstaafl

Try putting those lamps in the outside fixtures. Maybe you did get a bad batch. If the transformers are indeed identical, about the only other possibility I can think of is that maybe the outdoor fixtures are trapping heat, leading to premature failure of the lamps.

FWIW, running 12V AC instead of 12V DC does nothing to avoid voltage drop issues. Your heavy gauge wire is the only thing helping you in that respect.

Nailbird

Sorted it... the problem was moisture. The fixtures have a drain hole to allow condensate to get out, but we've had so much rain on the east coast water was flooding into the fixture and shorting out the bulbs. I'm using bollard fixtures and they have a design flaw that allows water to build up inside the lens. It's a waterfront house and it's salt water which aggrevates the problem. Not all fixtures were leaking, but the ones that were blew the bulbs. I sealed the fixtures with silicon and this morning all lights were on.

Thanks for setting me straight on the voltage drop issue - actually drop in an LV AC circuit should slightly more that the DC equivalent.

Tinstaafl

Thanks for letting us know!