Lighting question

[volcamp]

I am an electrical dummy. We are just finishing our riding arena and I need to install four 175W mercury vapor security lights. Due to logistics, I need to tap off of an existing line in our barn. This will require a run of about 100 yards to the arena. the existing line only has four electrical outlets on it with only a small refrigerator on the circuit. What size breaker/wire would i need to run the arena lights or is this even feasible with the existing circuit? Any and all help/ideas welcome. Thanks.

 

[Soundguy]

I'm flat on my back with acute bronchitis and don't have access to my manuals.. but look at your electrical load.. 4x175 = 700w.. almost 6a on a 120v line.

Is that a 20a circuit you have? Call the store you are buying the elec supplies from.. even box stores like HD/lowes should have a chart on the box showing wire size / run length. I'd be surprised if it was under 10/3..maybee 8.. etc..

I'm sure an electricain/inspector will post in with the exact info soon.. probably saving you the phone call.. etc.

soundguy

 

[tallyho8]

I recommend that you use four 100 watt high pressure sodium lights instead. You will get more light, use less electricity and be able to use smaller, cheaper wiring. I run mine on 240 volts instead of 120v so that the amperage draw is lower requiring lighter wire.

 

[Wayne County Hose]

I'm flat on my back with acute bronchitis....

soundguy

Wow, hope you feel better. One good thing, the bronchitis has improved your typing.

 

[ray66v]

High Pressure Sodium is the way to go, and you get a warmer more pleasing color of light. Mercury lamps have cold green tones, and will tend to be less effecient.
That is a long run for #12-2 wire at 120vac. But to run 4 lamps, 400-700 watts, if you want to save money, its NOT by the book, but, it will work. We have a pump running on that much wire drawing 10 amps and it works fine, (8 years). If you want to do it "right", go with #10-2 or More. If you can get 220vac from your source, and 220vac lights, then as a previous poster said #12-2 is plenty, But, remember with 220vac, if you ever want 110vac out there, you need #12-3.
Fuses/ Breakers for #12 is 20 amps (max), #10 is 30 amps (max).
If you bury the wire spend a couple bucks more and put it in plastic conduit.
it only takes 1 rock in the fill to possibly damage the line in the future. I think its cheap insurance. If it is damaged the hot conductors can "leak" to the ground and you will pay for electric you are not using. If you don't get frost, you could possibly go with direct burial.

 

[lovemytoys]

100 yards??rule of tumb is every 100 feet go up a size in wire.why not run a pipe with three #6 and put a sub panel ,this give you room to grow .but 4 175 watt light (i dont think)will hold by them selves.

 

[ray66v]

The "up a size for each 100 feet rule" is to get the full capacity out of the wire.
If you don't need that much power than it is not relevant.
If I did the math correctly the 4 lights even if they are 175 watts, (and HPS would be more like 100 watts), equals 6 amps. 6 amps at 300 ft. on #12 at 120vac is around a 5% voltage drop. The lights will work fine at that voltage.
If he goes with the 400 watt HPS he only has around a 3% drop, If it is a dedicated circuit, just for the lights, he does not need to get the whole 20 amps from the circuit he is tapping into back there. How much does he want to spend? I say buy the biggest wire you can afford. But, the least you can use is #12.
Sure, I think he should run #2 and put 220vac back there.
Its up to him.

 

[Soundguy]

Wow, hope you feel better. One good thing, the bronchitis has improved your typing.

I told you guys it was the cats making me type bad by walking along my desk and in my lap while I read/reply email... you didn't believe me! While I am convalescing with lung problems, I'm in bed.. and no cats are allowed inthe room.. just me and the laptop... and thus.. better typing....

soundguy

 

[lovemytoys]

175watt light are 1.6 amp at least .and he has a ref on it to that needs all it needs

 

[ray66v]

175watt light are 1.6 amp at least .and he has a ref on it to that needs all it needs

I'm sure I don't have any idea what this means? Please clarify

 

[lovemytoys]

ok 4 lights at about 1.6 amps=6.4 amps and a small refrigerator is about 4maybe 5 amps=11.4 amps at 110 volts .but when you have voltage loss your amps go up .then added the small power surge when the compressor comes on .now you are pushing it.

 

[ray66v]

ok 4 lights at about 1.6 amps=6.4 amps and a small refrigerator is about 4maybe 5 amps=11.4 amps at 110 volts .but when you have voltage loss your amps go up .then added the small power surge when the compressor comes on .now you are pushing it.

Good, I understand perfectly.
?Question, why are you including the refrigerator in the calculation? it is already wired, it will not be on the new line it it will not have much of any effect.
and the lights at 6 amps will not have much effect on the frige because it is up stream.
If amps=watts / volts , 175 /120=1.46 amps not to split hairs. and again if he uses HPS it will only be 400w and thats a no brainer.
If your still worried then, when you do it, use what ever you want.

 

[mopacman]

When you have voltage loss on lamps the amps goes down. The only time the amps goes up is when you keep doing the same work when you have voltage loss.....Larry

 

[lovemytoys]

Good, I understand perfectly.
?Question, why are you including the refrigerator in the calculation? it is already wired, it will not be on the new line it it will not have much of any effect.
and the lights at 6 amps will not have much effect on the frige because it is up stream.
If amps=watts / volts , 175 /120=1.46 amps not to split hairs. and again if he uses HPS it will only be 400w and thats a no brainer.
If your still worried then, when you do it, use what ever you want.

it all count it total load .the ref is going to be on the same feed .If amps=watts / volts , 175 /120=1.46 amps not to split hairs,that not with the voltage drop!i been doing this for enough years to know

 

[lovemytoys]

ok let see votage drop .now you have 98 volts x4-175 watt bulbs now we are at 1.78 amps

 

[mopacman]

when voltage drops the wattage goes down. The only time a bulb uses its rated wattage is when it is at rated voltage......Larry

 

[ray66v]

Yes, the frig, does count for total load on the front at the breaker but the voltge drop is at the end of the curcuit. It is going to drop after the frig. So, don't see it adding to the drop

 

[lovemytoys]

when voltage drops the wattage goes down. The only time a bulb uses its rated wattage is when it is at rated voltage......Larry

but the amps goes up

 

[Soundguy]

Hate to burst any bubbles here.. but at least for incandescent lamps.. we are looking at a fixed resistance that becomes stable when the filament is hot... that's the 1 fixed variable of ohms law you can then plug the rest in and play.... use a fixed 'r' and plug in different values of 'e'

Remember.. wattage is not constant... a 12v car battery and a house outlet don't make a 100w 120v bulb glow the same... by some of the logic I've seen thrown around here... they would glow the same.. but the car battery would be sourcing some big amperage....... which.. in practice... it won't.... due to the resistance of the filament.. once it settles down..

soundguy

 

[wedge40]

I'm by no means an expert, but I would agree with lovemytoys. With a panel out at the arena you can run your lights and if you need something else once in awhile you have the extra to do it. I'm not sure what the cost difference would be though.

Wedge