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Old 08-07-2020, 06:58 PM   #1
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Wiring Gauge

Hello, thanks for reading my post.

I'm very new to electrical wiring and wondering if anyone had any tips for wire size/guage.

I understand that all my 110v appliances use 12/2(?), or is that only for outlets?

I have a 12k BTU mini split, should I use 10AWG?

I used a calculator to determine what wire size I should use for some 12W flood lights. I need four total, one on each side of the bus (front/back/side/side). The calculator told me I would need 6AWG. I don't believe that's correct.

I'm very confused on how to wire the 12v system.

Can anyone help? Thanks.
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Old 08-07-2020, 07:13 PM   #2
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Use a 15A circuit for loads up to 12A. Use a 20A circuit for loads up to 16A.

You don’t want to exceed 80% of the ampacity of the circuit

A=W/V

15A use 14 GA wire
20A use 12 GA wire

For DC loads you’ll also need to account for voltage drop. Get the Blue Sea Systems wire gauge calculator.
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Old 08-07-2020, 08:11 PM   #3
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Originally Posted by dj2109 View Post
I have a 12k BTU mini split, should I use 10AWG?
Is it 110V or 220V?


Quote:
Originally Posted by dj2109 View Post
I'm very confused on how to wire the 12v system.
12W at 12V is 1A. Four of them would be 4A. Are the ratings of those flood lights correct? Doesn't seem right. What cable length did you enter into the calculator?
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Old 08-07-2020, 09:30 PM   #4
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The MiniSplit is 115v.

Something like this: https://www.amazon.com/Cutequeen-Lum...4&sr=8-37&th=1

I figured if I had to run them all on one circuit around the bus, that would be about 90 feet of wire, correct?
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Old 08-08-2020, 07:33 AM   #5
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The MiniSplit is 115v.

Something like this: https://www.amazon.com/Cutequeen-Lum...4&sr=8-37&th=1

I figured if I had to run them all on one circuit around the bus, that would be about 90 feet of wire, correct?
that would only be 90 feet for the last lite? or are they all at the of the wire?
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Old 08-08-2020, 08:05 PM   #6
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90 feet all around, connecting all four of the lights
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Old 08-08-2020, 08:57 PM   #7
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90 feet all around, connecting all four of the lights
the first part of the wire carries current for the 4 lites after the first lite the wire only carries current for 3 lites then after the 3rd lite the wire only carries current for 2 lites them 1 so the wire you are sizing for 4 lites will be overkill after the first lite. you should really talk to a electrician if your in over your head as you make a mistake you can burn it down while your sleeping in it
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Old 08-08-2020, 11:28 PM   #8
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the first part of the wire carries current for the 4 lites after the first lite the wire only carries current for 3 lites then after the 3rd lite the wire only carries current for 2 lites them 1 so the wire you are sizing for 4 lites will be overkill after the first lite. you should really talk to a electrician if your in over your head as you make a mistake you can burn it down while your sleeping in it
Huh?

Iíd just leave it at that, but I guess I should add some more commentary.

Mmore, are you saying that the circuit is carrying more load at the beginning than at the end? Iím no electrical engineer, but Iíd would say itís wise to treat the entire circuit as One and calculate accordingly.

4x36W=144W/12v=12A

For a short run like 10 feet or so you could do this on 14GA wire, but DC voltage doesnít travel well so you need to increase the wire size. You could do these calculations by hand. Hereís a good example

http://www.adamselectric.coop/wp-con...ltage-Drop.pdf

But for those of us that want the easy way out, are bad at math or want to get on with our day, get the blue sea system circuit wizard app for your phone.

After plugging in a few values, using the 90 foot RT it told me you need 10GA wire

And yes, always be safe with electricity. Always fuse your positive wires.
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Old 08-08-2020, 11:32 PM   #9
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I'm getting 4AWG when I plug in those values. Which I know is way too overkill for some LED lights
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Old 08-08-2020, 11:51 PM   #10
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I'm getting 4AWG when I plug in those values. Which I know is way too overkill for some LED lights
I used 10% allowable voltage drop. You used 3%

Minimum voltage on those lights is 10V. If you drop 10% youíre still delivering 10.8V
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Old 08-10-2020, 07:36 AM   #11
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I used a calculator to determine what wire size I should use for some 12W flood lights. I need four total, one on each side of the bus (front/back/side/side).
I believe you are asking about LED/SMD lights (12-24VDC). If so...

I've never understood the rating of these lights (9, 12, 18 watt, etc...) as they draw milliamps, not the .75 amp, 1 amp, 1.5 amp that the "watt rating" would imply (at least not in my experience). Here is an example/test that I performed several years ago.

I'd suggest get one and perform your own tests. You will find that you do not need "cable" (e.g. 6GA) to power them.
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Old 08-10-2020, 08:01 AM   #12
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Huh?

Iíd just leave it at that, but I guess I should add some more commentary.

Mmore, are you saying that the circuit is carrying more load at the beginning than at the end? Iím no electrical engineer, but Iíd would say itís wise to treat the entire circuit as One and calculate accordingly.

4x36W=144W/12v=12A

For a short run like 10 feet or so you could do this on 14GA wire, but DC voltage doesnít travel well so you need to increase the wire size. You could do these calculations by hand. Hereís a good example

http://www.adamselectric.coop/wp-con...ltage-Drop.pdf

But for those of us that want the easy way out, are bad at math or want to get on with our day, get the blue sea system circuit wizard app for your phone.

After plugging in a few values, using the 90 foot RT it told me you need 10GA wire

And yes, always be safe with electricity. Always fuse your positive wires.
the wire before the first lite is carrying current for 144 watts but after the first lite the demand drops to 108 as its only feeding 3 friggin lites. then after the second lite it drops to 72 as that wire is not feeding 4 lites only 2 so the current draw decreases after each load. this post is a good example of why he needs a electrician not this crap
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Old 08-10-2020, 11:13 AM   #13
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Whoa if anyone is going to be rude, please leave this thread

I’m looking for all angles of advice, not dispute. Thanks
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Old 08-12-2020, 08:25 PM   #14
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A couple of thoughts: You've gotten some good advice but in general AC power from the inverter doesn't care how far it goes, but DC battery voltage does. If you have AC powered things that are up to 15 amps you can use 14/2. 20 amps requires 12/2. Most AC systems for the roof are less than 20 amps but I would wire that on its own breaker, 20 amps, with 12/2 wire. I would wire pretty much everything else as 14/2 on 15 amp circuits unless you have specific needs.

DC is a bit different because of voltage drop. You can look at the chart and look at things to see what you need based on rated voltage and wire distance and figure it out. That being said, as long as you protect your wire with appropriate fuses you'll at least not burn anything down. If you have 14 awg wire, make sure your fuse is 15 amps or smaller. if you have larger or smaller wire you have to make sure that the fuse will pop before the wire burns, and that's the whole key to safety. Keep the fuses smaller than the wire and you'll blow fuses instead of burn down. Over-rate the wire for the devices a little bit and you'll be happier in the long run most likely.
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Old 09-03-2020, 12:33 PM   #15
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Higher voltages travel better over longer distances. This is because the voltage lost is the result of the resistance in the wire times the current. A higher voltage means smaller current for the same power. Thays why utility companies use transformers to boost line voltages to thousands of volts for transmission.

A 120W light pulls only 1A on a 120VAC circuit. A 120W light on a 12VDC circuit will pull 10A and need a larger wire.

If you want to learn basic electricity and have a resource for wire ampacity and formulas, get an "Ugly's Electrical Reference Book" at any building supply store. Its pocket sized.
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