Outdoor Lighting Woes

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Old 12-02-08, 06:33 PM
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Outdoor Lighting Woes

Hello, all...I need a little help! My wife and I bought a little horse farm in Texas, and the Thanksgiving break was a chance for me to get the arena lights working. I'm not an electrician, but I do have a number of years experience with basic farm/ranch/home wiring. Anyhow, I'm sure I'm not alone in my hatred for "going over" what someone else has already done. However, I dug up, and inspected most of the 6-3 direct burial, and fixed only one break. On the first flip of the breaker to power up the lights, it trips immediately. Upon resetting, everything works, for about 5 minutes...then the breaker trips again.

Here are the rough specs:

-8 total 500w halogen lights; 2 per pole x 4 poles.

-6-3 direct burial: from source (approximately) 10 feet to the first j-box, 50 feet to the 2nd j-box, 60 feet to the 3rd j-box, and 50 feet to the last box.

-Each j-box has less than 15 feet of 12-2 from the j-box to the pair of lights.

My first thought is that I have the correct wire, but my breaker is too small for the amp load. However, I don't want to just throw a bigger breaker in. The kicker is, I couldn't find the amperage info anywhere; no the box, the instuction sheet...even the product help-line guy couldn't find it. I was estimating 2 amps each, but I think I may have figured a bit low. The only info I could find online was generic at 2-3 amp load/per fixture. Any help is appreciated.
 

Last edited by LunchBoxmtbr; 12-02-08 at 07:19 PM.
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Old 12-02-08, 06:56 PM
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Originally Posted by LunchBoxmtbr View Post
Upon resetting, everything works, for about 5 minutes...then the breaker trips again. Here are the rough specs: -8 total 500w halogen lights; 2 per pole x 4 poles. -6-3 direct burial: from source (approximately) 10 feet to the first j-box, 50 feet to the 2nd j-box, 60 feet to the 3rd j-box, and 50 feet to the last box. -Each j-box has less than 15 feet of 12-2 from the j-box to the pair of lights. My first thought is that I have the correct wire, but my breaker is too small for the amp load.
You have about 4000 watts. At 120 volts that equals 33.3 amps. You would need a 40 amp breaker for that load. Since you put that it is feed with a 6/3 I'm guessing it is a multiwire circuit which would be 16.6 amps so it would have to be a 25 (or 30) amp circuit. I am guessing that these lights are 120 volt.
However since it tripped right away the first time I would suspect you have fault some ware.
Can you disconnect the lights on the circuit? That will tell you if the circuit is overloaded and if there is a fault in a light. If the breaker still trips, then you have a fault in your #6 feed.
Your wire is plenty big.
 
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Old 12-02-08, 07:06 PM
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Thanks for the fast reply. Pulling the bulbs out is the only way I can think of disconnecting the lights from the circuit. I normally wouldn't jump to increasing the breaker size as a solution, but I was afraid I under-estimated the amperage. Your analysis of the amp load (for those fixtures) is a little higher than what I've found from the internet (which is always 100% accurate )...so maybe this is one of those rare situations where upping the breaker size is appropriate.

Also, by "multiwire circuit" are you asking if I'm running one half on the black lead, and the other half on the red lead? *Sorry, my knowledge is somewhat limited!

*I've capped off the red wire, and running the entire circuit on the black wire @ 120v.
 
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Old 12-02-08, 08:17 PM
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With a multiwire circuit you have two hots (black and red) that share the same neutral (white) If your feeder (your #6/3) is on a 2 pole breaker you can divide the load between the hots cutting your amp draw in half because you have basically two 120 volt circuits sharing the same neutral.

*I've capped off the red wire, and running the entire circuit on the black wire @ 120v.
That may be your issue right there. Heres my math. 8 lights @ 500 watts = 4000 watts / 120 volts = 33.33 amps. Your breaker would need to be a single 40 amp (which you will have a hard time finding). If you divide the lights between the two hots you get 4000 watts / 240 volts = 16.7 which is over 80% of 20 amps so you would have to go one size larger breaker. 25 amps. This would be a 2 pole, 25 amp breaker BTW. Your wire is rated for 55 amps but I see not need to go there. I would suggest splitting them up between the two hots.

What size breaker is in there now? This is just for your lights correct? No outlets?
 
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Old 12-02-08, 09:46 PM
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Originally Posted by Tolyn Ironhand View Post
With a multiwire circuit you have two hots (black and red) that share the same neutral (white) If your feeder (your #6/3) is on a 2 pole breaker you can divide the load between the hots cutting your amp draw in half because you have basically two 120 volt circuits sharing the same neutral.
That's what I figured...but that would mean cracking open every j-box, and rewiring...oh man...I don't even want to think about it! Although <thinking out loud mode [on]>...if I get a 2 pole 25A, hook up the second leg with the red line, then connect the reds in the first j-box...I can hook up the red to the outgoing black in the second box, (making the 2nd box the end of that circuit) thus only really having to tap into 2 boxes. And, with #6 hooked to only 4 lights, voltage drop wouldn't be an issue. Hmmm...

Originally Posted by Tolyn Ironhand View Post
That may be your issue right there. Heres my math. 8 lights @ 500 watts = 4000 watts / 120 volts = 33.33 amps. Your breaker would need to be a single 40 amp (which you will have a hard time finding). If you divide the lights between the two hots you get 4000 watts / 240 volts = 16.7 which is over 80% of 20 amps so you would have to go one size larger breaker. 25 amps. This would be a 2 pole, 25 amp breaker BTW. Your wire is rated for 55 amps but I see not need to go there. I would suggest splitting them up between the two hots.

What size breaker is in there now? This is just for your lights correct? No outlets?

You are correct...just lights, no outlets, on a 20 amp SqD (Q).

I may go with your suggestion above. I'm going to install a cutoff switch this weekend anyway, so I'll be taking the breaker out already.

Thanks, and I'll let you know how it turns out.
 
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Old 12-03-08, 04:35 PM
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OK...another question...I have a double wide 30 amp breaker (for 240), but it only has one lever on it. I'm assuming this would still be ok, because the breaker affords protection up to 30 amps, over 2 circuits...it could care less what each leg is goint to. Am I correct?
 
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Old 12-03-08, 06:16 PM
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From what you describe you have a Square D QO panel.

Yes, it protects each leg of the circuit to 30 amps. If (such as your case) the black is pulling 33 amps and the red is pulling 0 amps the breaker will trip. If you divide the load between both the black and red, each will draw around 17 amps. No trip.

Of course, do not hook your 120 volt lights to both the black and the red. That will run 240 to them and they won't last very long!
 
 

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