Seems to be lot of knowledgeable folks here on Electrical circuits. Feed back would be much appreciated on this one.
I have a question..what wire size should I use?
Situation : Replacing underground wiring … ciruit has five yard lights..on a 60 amp circuit ( 60 amp fuse).
Distant from Fuse Panel to Lights..
Fuse – 60′ – 1st light – 175′ – 2nd light – 175′ – 3rd light – 190′ – 4th light – 220′ – 5th light
For a total cable length of 820′
Lights have 120v – 100W Balast w/Metal Haylide Bulbs. The present underground wiring is either #2 OR #4 Aluminum.
This is the way the devopler built it. The underground wiring was placed 6″ deep along the roads concrete curb , and isn’t in conduit. We have had wiring issues through the years and are done doing splicing repairs and want to trench and lay conduit and replace all the wiring.
We had one section replaced , between the 3rd and 4th Light ..a couple years back and the Electricial we hired to help..calculated the size we needed was # 10, which is what we used. But I ran these figures through a calculator tool
http://www.elec-toolbox.com/calculators/voltdrop.htm
and I get #4 …. and the tables in my Ref Book also indicate #4.
I wonder, maybe the electrician based the calculation on the fact that the other wire segments being as they were # 2 or # 4 and the voltage drop was so low that, maybe he thought #10 would be okay for the one segment?
So anyway the 60A fuse is just insane…I was thinking put in a 15A or 20A fuse and then go with #4 copper.
When we finish this we would like to do the same on our other Yard Light circuit …which is a 60A with 3 lights , and 560 ‘ of #2 or #4. I was thinking same thing 15 or 20A with #4 wiring?
Thoughts please. And thanks for reading!
Edited 9/17/2008 8:44 pm ET by Cuyahoga
Replies
60 Amp fuse?
What do the metal halides draw on start up?
Unfortunately your question is one I would not feel comfortable answering but hopefully one of the knowledgeable people will chime in.
you're both right, if your assumption is correct,
if you had one light at the end of that long run you would need to pull large wire all the way, but you can pull whatever you need as you get farther away from the source in order to keep VD low enough to run the lights
as for the 60A fuse? it was most likely used since #4 won't fit under a 15A lug
and one thing we do on pole lighting and roadway stuff, is use inline fuse holders similar to this:
http://host1.publiquik.com/bussmann_web/family.cgi?familyUid=558
at each light sized for the smaller load of course, and then the whole fixture doesn't become a fusible link
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This is an interesting arithmatic problem. You want a maximun voltage drop of 5% or maybe 3%. The entire equation revolves around the total amperage of the fixture -- not just the "100 watt" ballast. [The bulbs use electricity too.]
So the first step is to determine the actual amp draw of each fixture [ampmeter, google the maker, whatever...]. For now, let's assume that each of the five fixtures uses 1 amp. Therefore, the first 60' of run would carry 5 amps. The run between 1 & 2 would carry 4 amps; the run between 2 & 3 would carry 3 amps; the 190' run between 3 & 4 would carry 2 amps and the final run of 220' would have to carry 1 amp.
As you can see, each run will probably require a different size of wire and corresponding conduit.
The 60 amp fuse is very wrong. Somebody probably looked at the #4 wiring and assumed it was a high amp circuit. 6' is way too deep for the burial depth. You would need shoring for a trench over 5'.
~Peter
Vivaldi cheated. There are really five seasons.
opps i meant 6" , I edited my original post, thanks for bringing that to my attention...I'll put a clamp meter on there tonight or tomorrow and see what the actual current draw is ans post my findings.
Okay..the clamped on an meter last night and we are drawing 2A.
Note that because we have some bad wiring ( there is an open in the ground) we only have the first two lights in the circuit. We disconnect the wirings leaving the second light.
So that would be 2) 100 Watt lights with a total run of 350 feet .
Edited 9/18/2008 9:35 am ET by Cuyahoga
I'm not clear on this: "We disconnect the wirings leaving the second light." I don't know what the "6"" refers to?
Your meter shows 2 amps, but is this two light or one light fixture? This makes a lot of difference.
By the way, I used the calculator you referred to. Using Aluminum and 820' for the last light, I got #8 wire. I think for a 1 amp light. If you go to that site and click on "return to main page", then click on "Tricks of the Trade". Lots of nifty ideas there.
~Peter
Original I did a typo, I said the wire was 6' deep...I edited my initial posting to say, it was buried 6" deep.
As for the circuit in my original post I gave all the dimensions for all the lights....but then you wanted me to take a current reading...and at that point I wanted to make clear, that , since we had wiring issues after the 2nd light , we disconnected the wires feeding the the thrid light .
We did that at the second light, so I'm reading 2 A on a two light circuit.
If we had good wiring ( but we don't ) then all the lights would be up and functioning and then I could take a reading. But I'm assuming that if all 5 lights were hooked up, then it would be a 5 amp draw.
And then is it correct that I would need #4 wire? I mean someone mentioned that each segment of wire from Light to Light could be smaller guage..and the next segment a smaller guage and so on. But I thought that the calculator meant to use #4 on the whole circuit ( obviously the wire from the terminal thing to the Ballast ( at each post ) would be a much smaller guage.
Thanks for your feedback!
Edited 9/18/2008 10:51 pm ET by Cuyahoga
Edited 9/18/2008 10:53 pm ET by Cuyahoga
Edited 9/18/2008 10:54 pm ET by Cuyahoga
Edited 9/18/2008 10:59 pm ET by Cuyahoga
If at all possible I would replace the lights, or at least the ballast, with 240 volt units.That will drastically cut down the size of the wireAnd I would allow 5% voltage drop for this. You aren't starting a motor at the fair end and they lights don't need to be that matched, unlike runway lights.And I don't know the layout, but is there any possibility of getting a power drop put in at the mid point. Combined those ideas you can use #14 AL."I mean someone mentioned that each segment of wire from Light to Light could be smaller guage..and the next segment a smaller guage and so on. But I thought that the calculator meant to use #4 on the whole circuit ( obviously the wire from the terminal thing to the Ballast ( at each post ) would be a much smaller guage."Yes, the calculator assumes that there is the full load at the end of the circuit.You have a much different situation. You would need to break it up into individual segments and figure the load and amount of voltage drop that you will accept on each segment.BTW, 6" is way to shallow unless it is under a concret slab.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I see , thanks for the explanation...figure load at end of each segment and use the capculator tool for each segment....
I appreciate your time to explain!
And the 240 v is good idea, I'll look at pricing for 240 Ballast and figure it that way..could save a lot 0f $ in copper and also get down to a size where we can get a x-2 , G type cable which would save us money and be easier to run.
Edited 9/20/2008 6:40 pm ET by Cuyahoga
take a look at the ballasts you already have, they may be multi-tap s and you don't have to buy new onesI was doing some figuring and if you change the voltage to 240 and you can dig in a handhole j-box midway between #3 and #4 fixtures, you could run #10 all the way to that and then use #12 for the last two lightsone more question, how are these lights controlled ? time clock ? dusk-to-dawn ?.
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a photo-sensor at each light post
you will need to make sure those P/E are rated for 240 Volts, or install just one at the source of the circuit and eliminate all on the posts.
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well I re worked my calcs.. I forgot to halve the current..... and if you can rewire for 240 volts following the original feeder route you can run #12 Copper all the way to the last light ! #14 is just a bit too small for that long run if you take Hartmanns suggestion though and run a new feeder to that 3rd light ...... you could then run #14 from there to the other lights...... even using Aluminum but FYI #14 Aluminum was NEVER available even when houses were wired with the stuff, the smallest gauge was #12 The most practical would be to run #12,
change the voltage if the ballasts can be rewired,
and use just one photoeye or even something exotic like a solid state relay, which an electrician should wire up.
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". you could then run #14 from there to the other lights...... even using Aluminum"Now you done it. Fireball is going make you give up your union membership because you aren't a "real electrican"..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
hahaha ... just wanted to share in the fun !.
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One of my secret advisors did some "calculus" and came up with --
In the example case the last 220 ft. section can be replaced with 10 AWG copper to result in a voltage drop of 3.45 Volts and only 7% more copper than if the optimum (and unobtainable) conductors are used.
I think he used #8 for the rest of the runs. [But then he used copper.]
~Peter
Today two seasons start.
According to that voltage drop calculator, a 50’ run (one way) of wire for a 20 amp circuit should use 10 gauge wire.
But I’ve been in many modern houses where the kitchen is 60’ or more from the circuit breaker panel, and all of the kitchens' 20 amp branches (microwave, dishwasher, small appliance outlets, etc.) are always wired with 12 gauge. Why is that?<!----><!----><!---->
Edited 9/21/2008 12:18 pm ET by JDLee
Most times when I have check voltage drop up sizing is not needed untill you get to 75 to 100 ft.But you need to realize that none of the dedicate loads approach 20 amps and most can be run on 15 amp circuits.The except being the small applicance circuit as it needs to allow for multiple different devices.And there is no requirement in the code for max voltage drop. Just a recommendation..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Why would you think that going to a 240v ballast would drastically reduce the size of the wire? If he has 5 lights drawing 2 amps a piece and he cuts it in half by going from a 120v to a 240v ballast,or a quad tap for that matter,it's not going to change the size of the wire at all. I'm not sure how far a distance he is actually talking about here,he says it's 220' from the panel to the last light,but +800'of wire? You really didn't say he should pull #14 aluminum though right? No electrician would do that.
"Why would you think that going to a 240v ballast would drastically reduce the size of the wire?"Basic electrical engineering.First you cut the current in 1/2 you reduce the voltage drop by 1/2 for any wire size. Or you can use wire of 1/2 the area.Second by doubling the supply voltage you can have twice the voltage drop and still have the same percentage of reduction. Again allowing wire 1/2 the size.And last, but not least I said if they could change it to a center feed systems so that the length is reduced by 1/2. Again allowing wire of 1/2 the size."You really didn't say he should pull #14 aluminum though right? No electrician would do that."Well a good one will. Or at least see what is needed for the application. In fact UNDER THE CONDITIONS I GAVE #14 al would work. But I don't believe that there is any availalbe in small guage.All of those changes allow a wire of 1/8 the area of the orginal. Now I might have made a mistake, in the quick numbers, but it would be much, much less than had been used..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill, Again,if he has a load of 10 amps and he reduces it to 5 amps he's going to end up pulling the same size wire,not "drastically reducing the size" as you stated. I don't think #14 aluminum is even sold or manufactured.Let alone used by electricians. Your claim that a "a good one"(electrician) would use #14 aluminum is another example of you having some knowledge of theory and the NEC, but being absolutely clueless about how electrical work is actually done.I know you helped the neighbor lady with some wiring one time,but you're out in left field here.
" Your claim that a "a good one"(electrician) would use #14 aluminum "I NEVER SAID THAT."I don't think #14 aluminum is even sold or manufactured"What did I say..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"Bill, Again,if he has a load of 10 amps and he reduces it to 5 amps "You need to go back and READ IT.First the load is 5 amps. And the changes that I was suggesting would drop it to 2 amps."Bill, Again,if he has a load of 10 amps and he reduces it to 5 amps he's going to end up pulling the same size wire,not "drastically reducing the size" as you stated."Then YOU tell HOW the wire size is calculated.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The calculator the original poster provided a link for seems to work fine,so let's say he takes your suggestion and runs a feed out to the middle of the run,he would need #8 copper on 120v 1a fixtures.If he spends the time,effort, and money to replace the ballasts with ones that draw .5 amps he could pull # 10 copper out to the middle and drop to #12 copper going out to the ends.Not much of a savings let alone a "drastic" one.
I don't know how you figured #14 aluminum but that is what you said the guy could use.And when I said no electrician would actually do that,you quoted my words and then said that a good one would.I've done lots of parking lot lighting and have pulled actual miles of #4,8,10,(12's only when they were 480v poles) but never an inch of #14 or aluminum wire.
See, here's the thing about Breaktime the readers should understand: There ARE guys that DO framing,or drywall,or finish carpentry, or plumbing everyday and I myself have learned a lot from them. But there are also a LOT of people who have never done the work and offer all kinds of advice anyway.There's one guy(who hasn't offered his opinion in this thread thank God) who does offer advice in all kinds of threads here,including electrical, and is absolutely dumb as a post.
You do try to help people Bill, and I'll give you credit for that, but sometimes you bury your nose in the codebook and engineering websites,and you miss the mark, like here when this man is looking at replacing 800' of wiring and you tell him he can use #14 aluminum.
Sorry to ruin your fun. I do all those things you mention every week. I am in my third year for the electrical, and spent my last four weekends rebuilding dormer roofs.
I may be dumb as a post, but I'm laughing all the way to the bank.
Edited 9/23/2008 10:44 pm ET by arcflash
Arc, you're not the person I said was dumb as a post.
Good luck to you in your career.
You never said how going from #4 to #12 is not a drastic reduction in wire size..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Apparently the description fit. You certainly flushed him out.Why don't you hang around and post more. We need more people with real world practical experience.I didn't find out how little I knew about the electrical trade until I decided to get my master's certification. I was a graduate of an IBEW/NECA apprenticeship and had worked as a journeyman, foreman, and general foreman for fifteen years at that time.The studying that I did for the master's exam sure did open my eyes to a lot of things. Common practice in the field involved a lot of guessing when it came to figuring voltage drop or sizing wire.Chuck
Sure would, but I might not ever get the chance. My house is single phase 120/240. My job is 3 phase 110/208 four wire delta. I might see an industrial application for a 240V ballast, but most lighting circuits are wired on the "low leg" meaning A phase or C phase for a 3 phase system. If you think that you can just tie in to the 240V side of the multi-voltage ballast on a twenty amp single pole breaker, you might be in for a little surprise. I hope you've got extra ballasts.
Ohm's Law doesn't mention wire length. Voltage drop isn't even an issue until about 200ft. Then, a general rule is to go up a size. You guys are over thinking it.
Speaking of posts, my neighbor wants me to build her a fence. She saw mine and liked it. She liked the window I was putting in too, so now I'm replacing one for her. I like posts, I only buy magic ones that turn into cash.
whoooops, "My job is 3 phase 110/208 four wire delta "tell me that was a typo.as far as the present discussion goes, most of it has been merely an exercise with most of the responses being nothing more than suggestive, there has been very little overthinking.
and hopefully you have learned something from all of this, because it would be a real shame if you didn't, I have every confidence that the OP is now drinking heavily and banging his head on the bar wondering why he asked for help .......... in the meantime double check to be sure of the voltages you ARE working with.
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Did you mean to post to someone else?
I am sorry. I was wrong.It actually #16 AL.How this calulator only goes down to #14.http://www.elec-toolbox.com/calculators/voltdrop.htmBut this one goes down to #18http://www.csgnetwork.com/voltagedropcalc.htmlNow put in 410 ft, 1 amp load, and 240 volt supply, AL, and you get a 2.4% voltage drop with #16.But that same information into the first calculator and it comes up with #14."ou quoted my words and then said that a good one would.""Well a good one will. Or at least see what is needed for the application."Or determine what is needed.And I just showed where the calculator agrees with me.Anyway the whole thing was not an attempt to give a detailed How To.It was a list of a bunch of things that could be done to reduce the size of the wire. As I said I don't know if any of those could be done. But if it was done then that is when you need.I don't know what kind lights these are so no way of determinine what ballast where available. And even more probably is the possibility of center feed. Where is the POCO feed? Can a separate meter be used? Etc etc?I also said that by going to 240 ballast and relaxing the voltage drop a bit and unlike run way lights they don't have to be that exactly matched you might get even better.When looking at going from from 120 to 240 and keeping it in a linear layout we see that #12 CU gives up a 3.3% VD which is certain acceptable.And I don't know what you definition of DRASTIC is, but going from #4 to #12 is to me a DRASTIC REDUCTION IN SIZE.I also mention that he could be helped by computing the wire size in segments.All of it is an excersize in reducing the wire size. Not a step by step how to wire it.So get off you high horse..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Voltage drop has is only slightly related to Ohm's Law. That relatation is restistance, but is not in the Law itself. Voltage drop is a reduction in voltage or current due to resistance increased by an increase in the lenght of conductor. Voltage drop and resistance cannot be used interchangibly.
Also, the type of ballast used is determined by the voltage that supplies it, not the other way around. Ballasts are wired to common electrical service lighting supplies, and I have never wired a ballast to 240V.
"Also, the type of ballast used is determined by the voltage that supplies it, not the other way around. Ballasts are wired to common electrical service lighting supplies, and I have never wired a ballast to 240V."Now I have not idea what kind of lights these are. That is way I said if they are available.But I quickly found these.http://www.lightingsupply.com/ballasts/mercury_vapor_mv_ballasts.aspx"Mercury Vapor (MV) Ballasts
Print Page print viewMercury Vapor (MV) Ballasts imageLighting Supply does not carry Mercury Vapor ballasts at this time. However Mercury Vapor lamps will run on Metal Halide Ballasts. * Please see our selection of Metal Halide Ballasts listed below.
o 4-Tap includes 120V 208V 240V 277V
o 5-Tap includes 120V 208V 240V 277V 480V"http://www.superiorlighting.com/000010-Mercury%20Vapor%20Fixtures.htm"Voltage drop has is only slightly related to Ohm's Law. "WHAT????http://en.wikipedia.org/wiki/Ohm's_lawV (voltage) - I(current)x R(resistance).Change the amount of the current and the voltage drop changes.Change the resistance and the voltage drop changes.But this is the absolute voltage drop in the wiring.The amount of voltage drop that can be allowed in a circuit depends on the supply voltage.Assuming a 3% allowable drop then for 120 volt circuit you can have upto 3.6v drop.But on a 240 circuit you can have a 7.2 volt drop..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
uh, go back and reread the chapter(s) on Ohms Law VD has everything to do with Voltage Current, and circular milsand I think the reason you haven't hooked any ballasts up for 240 is only because you haven't worked on any old Delta services yet.....but I will grant you that putting a 400W pole light in somebodys yard isn't that common either.
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Arc, I have several florescent fixtures with 240v ballasts in them, if you'd like to try one for the first time.
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I knew you'd be here!!!
I was gonna say "ask billhartmann
I'm almost sorry I got into this mess. But using that calculator, there is no way that #4 wire is needed. What I got was: [assuming 1 amp per luminaire]
15 amp breaker
60' 5 amps #14
235' 4 amps #12
410' 3 amps #10
600' 2 amps #8
820' 1 amp #10
This is obviously wrong because these are fixed voltage drops for the given distances. Without more detailed calculations [Excel?], it would seem that running #8 to the fourth fixture and then #10 to the last one should do it.
Copper would give lower sizes. I would suggest using PVC at least 3/4".
~Peter