Help sizing wire

[tigerwoodKhorns]

I need soem help sizing some wires for an outdoor project.  I am adding 12v LED outdoor lighting.  The runs will be about 75 feet (need to emasure, maybe 100').  Each transformer will have about 10 1.5 watt LEDs, so figure 20 watts (I will upsize for a margin of safety).  I know that 14 awg will do is because the house is already wired with that for lighing circuits that are all loaded up (but at 120v). 

 

I just want to know if 16 ga or 18 will handle it. 

 

EDIT: Found this, looks like 16 ga will work for 100' runs wit the 2 88 watt transformers I am using.  I will be using less than 20 watts on each but this should solve the issue.

 

http://www.sprinklerwarehouse.com/Determining-Cable-Size-s/7929.htm

Edited November 3, 2014 by tigerwoodKhorns

[JL Sargent]

I think you've got it figured out with the chart. Actually a little voltage drop might be good for the lights themselves.

 

I'm working on a 120v outdoor LED conversion project myself. These lights had previously been high pressure sodium.  I'm going with the 14/2 direct burial wire. I'm installing four 14' decorative streetlights about 25' apart. 

[tigerwoodKhorns]

Nice.

 

I am putting stone veneer on the house and planning to repurpose my lights by changing to LEDs and putting them under the roof overhangs.  They should last forever there and look really good shinng down in the house's stonework. 

 

I know that you are going direct burial, but are you running conduit anyway?  Its low voltage so it doesn't need an inspection.  1/2" grey conduit is cheap and can make a future repair very easy if ever needed.

[tigerwoodKhorns]

Check these out.  Really simple to convert 120V lights to LEDs. 

 

I have lights next to my garage door that I am using these to convert to the small 2 pin bulbs (E4  / MR16).  I want less light out of these and more spotlights. 

 

http://www.amazon.com/Coromose-Socket-Holder-Adapter-Converter/dp/B00NKWYC4K

 

Then, here is a cool project to repaint your garage doors:

 

http://www.everythingicreate.com/p/garage-door-tutorial.html

[minermark]

Id run 12Ga period.

Do it once, do it Beefy, no worries.

[dtel]

Look around, sometimes the low voltage wire is sold in 100' rolls and is cheaper than most other wire, in the past I found some for the same price as 50' rolls, and think it was 14ga, but it's been a while.

 

I like the garage paint, looks much better.

Edited November 3, 2014 by dtel

[tigerwoodKhorns]

Id run 12Ga period.

Do it once, do it Beefy, no worries.

 

I always overdo it when building and try to never do things 2 times.  I just bought mortar that was 4 times as expensive as the cheap stuff because it has the polymers added. 

 

Here, I actually have a bunch of used 12 ga, but I will save it for the backyard. 

 

Remember that I am going from 150 watts down to about 15 or so with the LEDs, so the 14 ga (which is only a little more than the 16 ga) is complete overkill for this system. 

Edited November 3, 2014 by tigerwoodKhorns

[minermark]

 

Id run 12Ga period.

Do it once, do it Beefy, no worries.

 

I always overdo it when building and try to never do things 2 times.  I just bought mortat that was 4 times as expensive as the cheap stuff because it has the polymers added. 

 

Here, I actually have a bunch of used 12 ga, but remmeber I will save it for the backyard. 

 

Remember that I am going from 150 watts down to about 15 or so with the LEDs, so the 14 ga (which si only a little more than the 16 ga) is complete overkill for this system. 

 

"Remember that I am going from 150 watts down to about 15"

Yes, you are indeed going from whatever to whatever, I learned as a youngin, spend a little more/extra when doing the project the first time, that way no matter what kind of lighting you wish in the future, the wiring you do now gives you more flexabilty in the future. just my two cents learned from well over 1K houses in Irvine back in the day.

 

Just a side note:

Working/Leaning 40+ years ago, im on the job one day and ask my Boss why in the hell are we doing 14 for lighting and 12 for outlets? He stated it's the Minimum code, he was correct. so i ask him one day why not just wire the hole dam house in 12? simple obvious anser, was expense, so i ask just how much more expense? he says $100 per house minimum.

A year or so later im Lic and on my own, got some Irvine contracts, when the inspector shows up he see's i dont even carry 14Ga, he was impressed, some time later stopping by my jobs he would just walk up grab the permit sign off and leave, never looking at any of my work, old school goes a long way, do the extra mile.   

[dtel]

Working/Leaning 40+ years ago, im on the job one day and ask my Boss why in the hell are we doing 14 for lighting and 12 for outlets? He stated it's the Minimum code, he was correct. so i ask him one day why not just wire the hole dam house in 12? simple obvious anser, was expense, so i ask just how much more expense? he says $100 per house minimum.

 

Your right, when I wired ours I only used 12, it was really much easier to not even bother with another size, just keep pulling off the same roll. Now there even different colors to make the inspectors job easier.

[Fjd]

 

Working/Leaning 40+ years ago, im on the job one day and ask my Boss why in the hell are we doing 14 for lighting and 12 for outlets? He stated it's the Minimum code, he was correct. so i ask him one day why not just wire the hole dam house in 12? simple obvious anser, was expense, so i ask just how much more expense? he says $100 per house minimum.

 

Your right, when I wired ours I only used 12, it was really much easier to not even bother with another size, just keep pulling off the same roll. Now there even different colors to make the inspectors job easier.

 

 

 

I believe that the dynamic that probably comes into play in pushing for the 14ga over 12ga when 14ga is the minimum requirement is probably more related to the person that gets to put that additional $100 per house in their pocket.  If they can't bill for the additional cost and a markup they aren't interested and saving an additional $100 per job for using 14ga over 12ga for 1,000 jobs is an easy $100,000 in pocket.   

[bhenry]

............oh wait, there's also a little thing called "box fill" to consider when wiring an entire house with #12.

Just sayin'.

[minermark]

............oh wait, there's also a little thing called "box fill" to consider when wiring an entire house with #12.

Just sayin'.

in the 70s i paid no where near $100 difference, i was more projecting what it might be now.

As far as box fill? WTF? , i was never presented with the problem, and never had the problem.

12awg is not more than a 1/16 bigger than #14 OD anyway, conductor size is what it is, a few CM bigger.

Likely you have far more codes to deal with now then i had in the 70s.

[dtel]

I was never worried about box fill, keep it neat and there is plenty room, well it will fit put it that way.

 

Anyway I use 90% of the space anyway as far a breakers went, I always had way less on each breaker than normal so there is no chance of being even close to how they would normally wire a house. This came in handy later, if I wanted to add another outlet somewhere it was no problem to run it off the closest one, and this only happened once behind a counter. 

 

Wire got expensive, a 250' roll 12-2  wire went from well under $25 to over $125, the price of copped has come down some but it's still not cheap.

[JL Sargent]

Lots of good reasons to go with 14ga wire over 12ga or larger if it is the correct size. FIrst and foremost it is cheaper. Second it is much easier to work with! Third and don't ask me how I know this. The backhoe doesn't give a crap what gauge it is when cutting right through it.

 

I used wire rated for direct burial. I bought 250 ft of it for $75.00. Didn't use conduit but it's all good if you do. I posted this photo in the photography thread but since it's relevant here I will share again. I retrofitted these fixtures to 30w LEDs from High pressure sodium. So total 120W.

[dtel]

The backhoe doesn't give a crap what gauge it is when cutting right through it.

 

The backhoe don't care if it's in pipe either, one thing I will say I hate to strip the end of a wire when it's direct burial wire, it's a pain.

 

I haven't cut a wire with a backhoe yet but I did cut someone's 1 1/2" gas line in half with a trencher once.  I smelled the gas and took off running to the truck, got a wrench and cut it off before it found a spark. His contractor cut corners and buried it about 6" deep so he not mad at me.

[Taz]

I'm of the "Old School" where everything should be built to outlast my Grand Kids.  When I built my house, the smallest wire was #12.  It's my understanding that it will pay for itself in time over the #14.  Besides if you or someone else should decide to put something else in it would be nice to have wire large enough to handle whatever might become in use.  

 

I have run up against too much wire and too many connectors with power going through the box.  I prefer oversized boxes as they are easier for me to wire.

 

Gentleman I knew wired #10 for plug in's and lights.  He stated this was a mistake and made wireing much more difficult for him.

 

Remember;  Code is "Bare Minimum."  of what's legal.  If you're building for yourself I'd advise overkill.  I've been known to run wires inside a house for future electrical additions I might want to add in the future.  

[bhenry]

Yes, the codes are vastly different now than they were in the 70's (before I was an electrician).

There's no reason that you CAN'T oversize your conductors, but as someone who does this for a living (the original post is about low-voltage lighting and I'm not including that in this case) there are many reasons NOT to oversize your conductors.

In 99.99% percent of residential applications, #14 is more than adequate. I have been in houses that have been converted from gas lighting to electric lighting (original wiring) that was run with #14 and is still in fine working order.

I put the old, "I wired my house with 12 gauge" comment in the same league as the volunteer firemen that drive around in red pickup trucks with an a$$load of strobe lights all over them but then put their laptop in the passenger seat and head off to their office cubicle.

I'm not saying there is anything wrong with either of those ways of thinking (and I have total respect for ALL firefighters!), and you can wire your own house however you chose. But I would charge significantly more that an additional $100 if someone hired me to wire their house using #12 minimum and it would take too long to explain why.

[Taz]

I figure that if I should need to run a long cord that needs to be #12, I should have that size wiring in the house.Not real uncommon to use 2 one hundred ft cords around the house.   Of course you can go overboard with it.  Daughter had ceiling lamp that burn out.  Maybe I should state that the wire to the light looked smaller then any speaker wire I ever used.  Also the wire had gotten pretty hot by the looks of the insulation around the wire.  We got her a new light put in,  And told her no more 100 w  bulbs in a fixture rated for 60 w.  It's difficult to find good fixtures for more than 60 w.

 

Now I can understand that contractors have to make money.  It's the paper that allows most of us to eat.  But when it's my house I opt for #12 as the bottom of the barrel.  I don't buy it any lighter 

 

My brother has an electric Jack hammer.  He kept burning it up with 12 # cords.  So I gave him a hundred foot of 10 # 4 wire cord.  Now thats a heavy cord to pack around, but his Hammer lasts much longer between rebuilds.  If you rent his hammer you have to agree to use only his cord.  And if he catches you using a lighter cord on it, could be Fight on,  Don always did like to fight.

[tigerwoodKhorns]

Oh man, I turn my back and look what happens. 

 

I know that this has gotten off topic, but in my situation, I am going to run 14 AWG where 16 will be over kill.  Remember, I am using LED's which draw a fraction of what was drawn in the past.  If I draw 20 watts I have gone too far. 

 

These wires will also be in conduit and installed under my roof overhangs (I am putting accent lighting in) so they can be repulled at any time. 

 

The 14 AWG is a few bucks more.  The 12 AWG is way more expensive.  If I do any burried wire in my back yar, I will probably go with the 12 because they cannot be re-pulled.  I already have it pre-wired with 12 GA around the perimeter. 

Edited November 8, 2014 by tigerwoodKhorns

[twistedcrankcammer]

I recommend 8.5mm Wire with an MSD 7-AL Box

 

Roger

Edited November 8, 2014 by twistedcrankcammer