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Old 08-21-2009, 03:57 PM
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East Coast Lawn Choppers East Coast Lawn Choppers is offline
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Light bulbs not lasting... Help

We did a patio for a customer. They had a transformer that they bought somewhere. We put lights in the patio (that match the cobble) , and a few step lights. Then an electrician came in and put lights all over the place. Now my question....
Are AC and DC and DC bulbs interchangable and to what extent. A few of the lights had halogen or xenon bulbs, the patio lights have what looks like a normal incadesent bulb (like a large 194 style). The step lights use a 194 sylvania which is the same as what a car takes 12v dc. No LED's in the circuit....
The transformer is a 12v AC 1200w with a few cuircuts and a eye and also a programable timer. The problem we had is the 194 12v bulbs all blew out in less than a year. Then the xenon or halogen bulbs got so hot the one melted the socket... I measured the voltage with the whole circuit energized and it is right at 12V AC. Almost the same right at the bulbs because we ran 12 ga wire to all of the lights.
As far as my background I have an electronics degree and spent ten years working on lasers that cut ceramic along with all other machinery, but never had to mess with low voltage lighting...
I know this probably sounds dumb but....
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Old 08-21-2009, 04:03 PM
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where are you measuring the voltage at ? How many watts are on the 12ga circuit ? Something tells me your using the wrong lamps or over volted. This is what happens when you supply some stuff... the electrician supplies some stuff and the homeowner supplies some stuff.

Could also be some of the lights were hooked up in series vs a more suitible method ? If thats the case your lamps could esentially be working as fuses.
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Old 08-21-2009, 04:19 PM
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I measured the 12v at the transformer and it is the same at the bulbs. The wiring is only 10-20 feet long and it is 12 ga. wire. They are all in parallel, one circuit has 3 12v 3.9w bulbs and 2 12v 6w bulbs all in parallel in on a 15' 12 ga. then the second has 4 12v xenon bulbs in parallel on a 12 ga. wire they are spaced at 4' 8' 12' and 16' on the wire. The third circuit has 8 12v 6w bulbs on a 12 ga wire they are wired in parallel 1st at 8' 2nd at 12' third at 16' 4th about 20' they each have two bulbs in each light.
They shouldn't be able to pull more current then they need should they ? If you put one bulb on a 1200w transformer it won't pull 1200w thru the one bulb correct ?
Hope this info helps...
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Old 08-21-2009, 05:08 PM
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No it will not pull more than it "needs" IF it is wired properly.

You said you have 4 lamps at 12v... what is the wattage tho. How are you checking the voltage at the lamps ? Under load or at no load ? Sounds to me like you have crappy lamps and since its so close to the transformer and such a small wattage lamp you might be over volted.

You say you have 12v... Are you SURE you dont have 12.5 or 12.8 etc... If so your over volted thus causing permature failures in the system. Typically we try to run in the low to mid 11v but alot of guys say 10.8 to 12v is acceptable. I never push the 12v envelope and stick to mid 11's and my lamps last 2 years or more.

NOW... it seems to me and in my experience the smaller the wattage the more delicate the lamp is. This is why I run my 10w mr16 lamps at a lower voltage. This is the only way I have found to get them to last longer.

If your over volted and there is no tap lower on the trans to lower the voltage you would need to either use a dimmer on the 120v side (ASSUMING THE TRANS IS DIMMABLE) or... increase the load/wire lenght on the low voltage side to increase your voltage drop.

Sounds like that 1200w trans they bought is way overkill for the tiny 3.9w lamps... I mean what kind of useable light would you get out of that anyways. Further something more that would concearn me is you mentioned melted sockets ??? Sounds like they are in need of a new system before it becomes a fire hazzard.
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Old 08-21-2009, 05:45 PM
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Beings it is a timer transformer I doubt I can dimmer the input. How can I put either more of a load on it or can I just put a dimmer or resitor inline on the output side ?
The 4 lights 12v on the one string are Pinnacle GL-120's w/ 12volt 35w jc pin bulbs. That is the one that melted the socket. The owner said that they get so hot you can't touch them, they will take your skin off... They look like half a ball with the bottom half having a lens, and are mounted on a wall. The way we wired it (soldered and heat shrinked the connections I really can't get my meter on the light bulb itself to get a true voltage reading at the light socket, but it can't be more than 12v because that is all I'm measuring at the transformer. Is a 35w too much for inside such a small aluminum light ? It would have to get hot wouldn't it ?
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Old 08-21-2009, 06:01 PM
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I am not familiar with that fixture... is it rated for that lamp and 35w or is it rated for something else.

a 35w halogen lamp can easily burn skin. One night a couple months ago I was adjusting a system and happened to be in flip flops because we know the clients well and I happened to drop a hot mr16 35w lamp on the ball of my ankle. In all of 2 seconds it burned down 2 layers of skin and I still have a quarter sized scar from it.

Sounds to me like the system was constructed using substandard mix and match components with too many people involved.

What transformer are you using ?
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Old 08-21-2009, 06:48 PM
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The light came with that bulb. Just for the heck of it I put the one I have here onto a small 12v transformer I have here (wall transformer) it does get very very hot... no wonder it melted the rubber coating on the wire... I think it is a cheap light fixture... that is probably the biggest problem. What I think actually happened was one bulb blew out and within about a week another then once two went out she said another one went each day. So I figure the load decreasse voltaqge rose and caused the problem. What started it was the one patio paver light (hi dollar light) had the stupid crimp on connector from the factory. Well after about 11 months one of them lost connection and then a few days later another did at that pinot it lost 4 bulbs decreasing the load on the system that took out the three 194 bulbs.... I didn't think back on all that... you just reminded me of it asking the questions... I didn't measure the voltage of the system with a few bulbs out of it. Tomorrow weather permiting I'll try to remove three of the circuts and see what the voltage is with only one for a load. I'll also check here and find out what transformer it is. I think it is a good one becauseit is a stainless steel box with a nice photo cell and a timer so that you can set it to stay on all the time it is dark or have it turn off after 1-? hours after it turns on which is nice. I'll get the name and let you know...
Thanks
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Kubota loader, mikasa plate tamper 7600#
Kobelco mini excavator
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Old 08-21-2009, 06:53 PM
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Sounds like a combination of over voltage and cheap import bulbs. Most of those bulbs are more comfortable and last longer volted in the mid to low 11s.
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Old 08-21-2009, 07:14 PM
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any time you start losing lamps on a run the voltage will increase. This is why I still preffer low to mid 11's even with a quality lamp. I have a few systems out there with fixtures within spitting range of the trans. These always eat lamps fastest because I am stuck with 12v.

Another solution might be to find a trans with an 11 or 11.5 volt tap.

a note on fixtures... a quality well designed fixture is made to take the heat in which it is rated. Still really curious to know which trans your running. Sounds to me like you only have a 12v out put and not multiple taps.
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Old 08-21-2009, 10:26 PM
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It has 12v 13v 14v and 15v taps. nothing lower than 12v
It is a Best Pro Lighting Transformer... but my bad on the watts.... It says 600VA which is total I thought looking at it that it was 600 ea. 1200 total. I have the website for it but don't know if I am allowed to put that in here. I went out and looked at it and found that they are two 300W transformers and only one is being used so it is only 300W's but it is 12,13,14,15 multi tap and I looked at the wire I used and he used and it is all 10ga. not 12 as I thought previously. So it'll even be harder to get a voltage drop with AC traveling 20' or less thru 10ga. wire and only putting a total of 230W's load on it.
Can I just put a dimmer or resistor in series with it to drop voltage ?
Incandesent bulb is a pure resitive load correct ?
Kind of having a brain fart right now but.... Voltage squared divided by 60W (the 60W would take me to 290W load) would come out to a 2.4 ohm resistor with the resistor dropping 2.5V roughly or is my brain out to lunch right now... been about ten years since I did any ohm's law since I left electronics and went back to landscaping... I'm thinking the parallel load is a combined 230W load so the resistor in series if it was a pot I could adjust it to the desired voltage but the pot would have to have up to a 70W rating. Correct me if I'm wrong...
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Kobelco mini excavator
Bobcat T190, Rockhound, ambusher, auger, jackhammer
Ingersoll Rand 185 air comp.
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Last edited by East Coast Lawn Choppers; 08-21-2009 at 10:33 PM.
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