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08-07-2020, 06:58 PM
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#1
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Skoolie
Join Date: Jun 2020
Posts: 145
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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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08-07-2020, 07:13 PM
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#2
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Bus Geek
Join Date: Sep 2018
Posts: 2,831
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
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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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08-07-2020, 08:11 PM
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#3
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Bus Crazy
Join Date: May 2017
Location: Athens, TN
Posts: 1,574
Year: 1999
Coachwork: Amtran
Chassis: International RE
Engine: International T444e
Rated Cap: 76
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Quote:
Originally Posted by dj2109
I have a 12k BTU mini split, should I use 10AWG?
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Is it 110V or 220V?
Quote:
Originally Posted by dj2109
I'm very confused on how to wire the 12v system.
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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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08-07-2020, 09:30 PM
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#4
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Skoolie
Join Date: Jun 2020
Posts: 145
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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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08-08-2020, 07:33 AM
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#5
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Bus Crazy
Join Date: Mar 2017
Location: arkensas
Posts: 1,071
Year: 1997
Coachwork: bluebird
Chassis: chevy
Engine: 3116 catapillar
Rated Cap: 71 now 2 humans 1 cat
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Quote:
Originally Posted by dj2109
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that would only be 90 feet for the last lite? or are they all at the of the wire?
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08-08-2020, 08:05 PM
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#6
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Skoolie
Join Date: Jun 2020
Posts: 145
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90 feet all around, connecting all four of the lights
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08-08-2020, 08:57 PM
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#7
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Bus Crazy
Join Date: Mar 2017
Location: arkensas
Posts: 1,071
Year: 1997
Coachwork: bluebird
Chassis: chevy
Engine: 3116 catapillar
Rated Cap: 71 now 2 humans 1 cat
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Quote:
Originally Posted by dj2109
90 feet all around, connecting all four of the lights
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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
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08-08-2020, 11:28 PM
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#8
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Bus Geek
Join Date: Sep 2018
Posts: 2,831
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
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Quote:
Originally Posted by mmoore6856
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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Huh?
I’d 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? I’m no electrical engineer, but I’d would say it’s 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 doesn’t travel well so you need to increase the wire size. You could do these calculations by hand. Here’s 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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08-08-2020, 11:32 PM
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#9
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Skoolie
Join Date: Jun 2020
Posts: 145
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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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08-08-2020, 11:51 PM
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#10
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Bus Geek
Join Date: Sep 2018
Posts: 2,831
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
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Quote:
Originally Posted by dj2109
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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I used 10% allowable voltage drop. You used 3%
Minimum voltage on those lights is 10V. If you drop 10% you’re still delivering 10.8V
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08-10-2020, 07:36 AM
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#11
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Bus Crazy
Join Date: Feb 2017
Location: The West
Posts: 1,210
Year: 1998
Coachwork: MCI
Chassis: 102 EL3
Engine: DD 60
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Quote:
Originally Posted by dj2109
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).
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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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08-10-2020, 08:01 AM
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#12
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Bus Crazy
Join Date: Mar 2017
Location: arkensas
Posts: 1,071
Year: 1997
Coachwork: bluebird
Chassis: chevy
Engine: 3116 catapillar
Rated Cap: 71 now 2 humans 1 cat
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Quote:
Originally Posted by Danjo
Huh?
I’d 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? I’m no electrical engineer, but I’d would say it’s 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 doesn’t travel well so you need to increase the wire size. You could do these calculations by hand. Here’s 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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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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08-10-2020, 11:13 AM
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#13
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Skoolie
Join Date: Jun 2020
Posts: 145
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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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08-12-2020, 08:25 PM
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#14
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Bus Nut
Join Date: Sep 2017
Location: Cerrillos, NM
Posts: 393
Year: 2002
Coachwork: Amtran
Chassis: Front Engine
Engine: DT466E
Rated Cap: 72
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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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09-03-2020, 12:33 PM
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#15
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Mini-Skoolie
Join Date: Nov 2014
Location: Texas
Posts: 48
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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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