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offgrididaho
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# Posted: 1 Jan 2019 05:38pm
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As I work on my schematic for power for our cabin (24v, solar and generator as inputs to charge batteries, through inverter/charger to regular household panel) it sure looks like I will have some relatively high current DC wires crossing over each other as I wire all the parts together mounted on the wall.
Is there a "best practice" for how to do this? Do I have to worry about it? It's an issue on boats (where my limited electrical knowledge comes from) because of chafe that can harm the insulation and then you have high current positive and negative wires touching, mucho bad. But maybe it's not an issue for a cabin since there's basically no movement and no chafe potential? Or should I be considering using conduit where positive and negative DC have to go over/under each other?
Anyone have good pictures of their final installation for where all your components (solar charge controller, inverter/charger, batteries, switches, fuses etc) are actually wired and mounted for your system?
I'm attaching my (current) schematic so you can get an idea of what I'm trying to wire all together.
-- Bass
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Cowracer
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# Posted: 1 Jan 2019 05:49pm
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Cabins don't move.
You don't have to worry about them chafing, but to be sure, give them a couple turns of Vulko-wrap to ease your mind
Tim
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offgrididaho
Member
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# Posted: 1 Jan 2019 06:01pm
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Quoting: Cowracer Cabins don't move.
You've never seen my shed 
Thanks...
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toyota_mdt_tech
Member
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# Posted: 1 Jan 2019 06:10pm
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High and low voltage cant run together in the same box or conduit.
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Atlincabin
Member
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# Posted: 2 Jan 2019 10:07am
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I have my solar DC wires in conduit together. Typically around 400V DC going through them. Standard 10ga solar wire. As noted, cabins don't move much so chafe points are not an issue, especially in conduit. Perhaps if the wires were hanging in the wind it could be a potential worry.
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toyota_mdt_tech
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# Posted: 2 Jan 2019 01:33pm
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Not saying it cant be done, its not code. And can be a hazard. As long as one knows it going it, aware of the hazards and if you ever sell it...
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Atlincabin
Member
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# Posted: 2 Jan 2019 06:12pm
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Toyota, are you saying my installation is not to code? If so, can you point me to the appropriate section of the NEC? Most solar installations have a maximum DC voltage of 600 is my understanding of the NEC.
Thanks,
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toyota_mdt_tech
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# Posted: 2 Jan 2019 10:00pm
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NEC code may have changed too. I have been getting several different answers.
https://www.homepower.com/articles/solar-electricity/design-installation/code-corner- wiring-systems-nec
This one might be the best. Not sure if it has the exact answer either.
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Atlincabin
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# Posted: 2 Jan 2019 11:00pm
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You're right, not a clear answer there. My basic (the caveat here is that I'm not an electrician, but I have done a lot of wiring over the years) understanding is that a lot of folks don't like a combination of AC and DC in the same conduit and I agree with that because its too easy to make a mistake and cross wires or otherwise hurt oneself. The current system I just installed is on my roof and the power cables (10AWG) go from the panels (actually from the SolarEdge optimizer boxes) in series into a junction box through a waterproof grommet and from there down the outside of the house in 3/4" flexible PVC conduit into the inverter. I also have a #6 ground wire from the array that goes into the conduit and to the inverter. This was as designed by my solar provider and was recently approved by the state inspector. I am presuming they know what they are doing, and therefore under the assumption that it is to code. It seems reasonably safe to me, but I'm always open to learning something new that is potentially safer/better.
Cheers,
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toyota_mdt_tech
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# Posted: 3 Jan 2019 08:29am
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If your solar guy designed it, I bet its all good. I am sure those guys have all this stuff down. They would know the latest code for this stuff.
Cheers back at ya atlincabin.
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Cowracer
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# Posted: 3 Jan 2019 09:10am
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FYI, In industrial plants that I usually work in NFPA 70E allows running anything under 600v in the same conduit. I have 460vac lines and a 24vdc line in the same conduit all over my plant. We try to segregate them when possible, but sometimes its simply not possible.
Now... Low voltage signal wires (i.e. communications cables, sensor cables, etc) are usually segregated to eliminate the small possibility of cross talk induced spurious readings.
Tim
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ICC
Member
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# Posted: 3 Jan 2019 09:55am
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Tim is on the right track. NEC places wiring into types that determine whether or not the can be together or not. They have Class 1, Class 2 and Class 3. It's the class more than being AC or DC or high or low voltage. It can get very confusing. I understand some and the rest is above my head. some info
another
And to make things more confusing there are Class I, Class II and Class III rules which are to do with types of hazardous locations.
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beachman
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# Posted: 3 Jan 2019 10:21am
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I am certainly no electrician and I have tried very hard to keep things safe so...I have everything in 12 volt going into one box, then for anything on AC, on to my inverter - then from the inverter, to a second box with breakers of their own to the various plugs, lights around the cabin. The first box has breakers for my CC, the main to the batteries, and to my 12 volt water pump in my loft. My 12 and higher voltage stuff is completely separate. Cabins do not generally move, but little vermin do - tend to take a shine to insulated wire.
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Cowracer
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# Posted: 3 Jan 2019 11:28am
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Quoting: ICC nd to make things more confusing there are Class I, Class II and Class III rules which are to do with types of hazardous locations.
Those deal with locations more than wiring. Class 1 deals with hazardous gasses, Class 2 is hazardous dust or particulate, and Class 3 is combustible fibers. Each class is broken up further by dividing in to 2 divisions. Div. 1 is the combustible material is present in ignitable quantities as a normal part of operation. Think oil refinery. Div. 2 is the materials only exist in ignitable quantities due to a process upset or failure. Think Self-Serve gas pumps.
I have spent way too much of my life tying to get sensors and other equipment safe for Class 1 Div 1 areas. What a huge PITA, but I guess it's better than blowing the hell up.
Tim
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toyota_mdt_tech
Member
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# Posted: 4 Jan 2019 09:09pm
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Cowracer, thanks for all the good info. 
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