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Old 07-26-2021, 02:11 PM   #1
Mini-Skoolie
 
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Need some basic Skoolie wiring info

I have a friend that is gutting a bus to build himself a Skoolie. He knows nothing about wiring and I have offered to help him out. What I know about wiring comes from wiring my home, some sailboats and an RV.

My friend's plan is to use a free role of Romex, install solar and a generator, run Romex and put a cheap $100 Craigslist fridge to be run off a 3000w inverter.

My instinct is to design a system that relies on DC powered items as much as possible and avoid a reliance on an inverter and or generator and run stranded wires.

I am going to guess there is all levels of build quality, is there a consensus of the best way to wire a Skoolie?

What is a reasonable budget for wiring and components for a Skoolie?

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Old 07-26-2021, 02:49 PM   #2
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Invite him into this forum to get first hand feedback.

What kind of battery?
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Old 07-26-2021, 03:14 PM   #3
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Thanks already have

I did invite him here, but decided to pave the way for him by asking a question first. We only chatted briefly last night via a messaging app. It sounds like he watched a YT vid and is trying to emulate what he saw there. I have watched enough bad YT videos to know there is a lot of bad advice out there, and felt a forum was a better place to get good advice and maybe a variety of options and opinions.

I saw your post on another question and was going to direct him to it that thread, as you were giving sage advice.
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Old 07-26-2021, 03:26 PM   #4
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I think we all appreciate your desire to help your friend but there are so many unknowns that I don't think anybody here can give you really helpful information. Is he going to run this off solar? How big is the battery bank and what type? What is the idle current draw of that inverter? What's the draw of the fridge? There are probably 15 more relevant questions we would need answers to, but I'm trying to guide this a bit from my phone. See what you can find out and share it here.
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Old 07-26-2021, 03:27 PM   #5
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The first thing necessary in designing any aspect of a skoolie, including the electrical system, is to determine the MISSION GOALS of the end project.


Is the MISSION the occasional weekend trip to a full hookup camp ground?
Is the MISSION full time off grid self sufficiency?
Or is it something in between.


The MISSION will determine what's needed and what "will do". For instance, that $100 craigslist fridge is likely to be very inefficient. If planning long term off grid it's probably no good but if the plan is to spend the occasional weekend with full hookups it might be perfectly acceptable.


Every decision should have a MISSION fulfillment factor involved.


So first step, determine what's the MISSION. THEN start figuring out the electrical.
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Old 07-26-2021, 05:07 PM   #6
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Quote:
Originally Posted by HamSkoolie View Post
So first step, determine what's the MISSION. THEN start figuring out the electrical.
I don't know his actual plans but his idea of using a $100 fridge to save money and free Romex to save money. I don't get the feeling he plans to be plugged in at a resort often, which is why my initial suggestion was to steer him away from using $100 fridge but he is "going to have solar, a generator and a huge battery bank."

I want to set him up for success and give him some reasonable expectations.

Is it likely he could wire his bus for less than $5000?

Is using Romex on a Skoolie up to code?
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Old 07-26-2021, 11:07 PM   #7
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Originally Posted by Photobug View Post
... I don't get the feeling he plans to be plugged in at a resort often, which is why my initial suggestion was to steer him away from using $100 fridge but he is "going to have solar, a generator and a huge battery bank."

I want to set him up for success and give him some reasonable expectations.

Is it likely he could wire his bus for less than $5000?

Is using Romex on a Skoolie up to code?

"...solar, a generator and a huge battery bank" is subjective. Some call those little lithium power packs with a built in 110 outlet a "generator" (some differentiate and call them "solar generators"). "solar" could mean anything.... I've seen systems described as "massive" that had 300W. And a "huge battery bank" doesn't mean it will be a good one.



I think you CAN wire a bus for less than 5k, probably a lot less, but you're not going to have large (efficient) battery banks, efficient inverters and solar systems, and you're going to need to do a lot more work to get the most out of it than if yo buy some expensive components with the bells and whistles.


As for romex, it's not optimum but there are lots of mobile 110 installs out there using it and a good number of them are manufactured by the RV industry. Just be sure to account for bouncing and movement..... protect against abrasion, connection contamination, and pulling as well as GFCI everything that can be (some motors can't be on a GFCI and an external outlet for say a welder probably won't work. THHN would be better but it will also cost more....and thus we see romex in mobile installations, many of them very nice installations.
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Old 07-27-2021, 02:32 AM   #8
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A two cents input:

Plan out your needs as already suggested. use wire that can carry the current you wish to use. follow guides for commercial wiring (use conduit, good electrical panels) plan your layout to minimize your wire lengths (also plumbing) Protect ALL circuits with circuit breakers. For 12 v wiring also protect all circuits with circuit breakers or fuses.

If you wish to operate from multiple sources (shore, generator, solar battery, inverter) design your system to NOT use outside/generator/inverter at the same time. Assure that no two sources can be connected at the same time. If using solar its OK to charge batteries anytime in daylight and have RV charger also charging batteries If the battery voltage get to full charge levels the solar charge controller should not overcharge, nor should the RV charger.

Once again, use large enough wire. Conduit will protect the wiring from chaffing.

Figure out in advance what lighting you want, and determine how much current is needed to support that. larger gauge wire is better than smaller gauge wire.



Can you do all of your electrical for less than $5K ? Probably. (generator, inverter solar)
I think the electrical system is the most expensive part of your conversion. But size it to your needs.
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Old 07-27-2021, 01:39 PM   #9
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Originally Posted by HamSkoolie View Post
As for romex, it's not optimum but there are lots of mobile 110 installs out there using it and a good number of them are manufactured by the RV industry. .

So you are saying not great but you can run romex for 110 in an Skoolie? I am pretty sure it is either a code violation or at least you need to de-rate romex if it is in conduit.

My friend was not aware romex had 3 conductors and normal DC runs only needs two wires. I think he was expecting to use Romex for all his wiring. Does anyone run romex for DC and just ignore the ground wire?
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Old 07-27-2021, 02:59 PM   #10
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AC can be used, more or less, for longer distances with smaller wire sizes. YOU MUST DO YOU HOMEWORK to see if the wire size you have is suitable for what you are using it for. Romex is fine for AC

DC wire sizes are much more dependent on wire diameter and length. Solid wire is not recommended for DC. YOU MUST DO YOUR HOMEWORK.

If you friend is going to do solar he needs to do a lot of studying to get it right. It isn't particularly hard but, you do need to know what you are doing.
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Old 07-27-2021, 04:20 PM   #11
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Quote:
Originally Posted by Photobug View Post
So you are saying not great but you can run romex for 110 in an Skoolie? I am pretty sure it is either a code violation or at least you need to de-rate romex if it is in conduit.

My friend was not aware romex had 3 conductors and normal DC runs only needs two wires. I think he was expecting to use Romex for all his wiring. Does anyone run romex for DC and just ignore the ground wire?
Look, don't run Romex just because you have it.

Before I got our bus I collected things I thought I could use. I quickly learned that doing my homework and doing the math gave me greater confidence that the wire and plumbing I install is not going to be ripped out because I missed something.

The primary wiring between batteries, inverters and solar charge controllers should be well-designed and none of it should be Romex.

That leaves the DC branch circuits for devices like lights, pumps, fans and other things. On my rig I calculate the wire size for every wire, and use that size or better. Being in the know on what the current needs are, and what the current-carrying capacity of the wire is, those are vital bits of information.

For AC circuits, yes, I have Romex left over from building my house and I'll use that for the branch circuits. There's some debate elsewhere here in the forum about using Romex at all; similar to the debate on gas piping (flex, black iron, or other). Not sure we'll have full consensus ever, but for DC circuits I draw the line: don't use Romex.

And while I'm at it, don't use switches or circuit breakers designed for AC circuits either (except on AC circuits). There are very good technical reasons why, and they boil down to premature failure of the switches and breakers.
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Old 07-27-2021, 04:55 PM   #12
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Look, don't run Romex just because you have it.
Thanks that is what I want to hear. I think my friend thinks a roll of Romex has his wiring needs covered. I want to make sure the build is done right, not something that gives trouble or brings down the value of the build. I have wired my entire house so I know how to use romex. It is fine for a home but when I see it in a boat or RV I realize someone has cheaped out on the electrical build.

I am hoping to help him build a quality electrical system. If budget is a concern, pull the correct wires where needed then add systems as budget allows.
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Old 07-27-2021, 05:57 PM   #13
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So you are saying not great but you can run romex for 110 in an Skoolie? I am pretty sure it is either a code violation or at least you need to de-rate romex if it is in conduit.
I would never consider putting romex inside conduit so I've never even considered that question. As for romex in an RV (skoolie in this case), FOR AC circuits, it's in use in the RV industry so unless they are all building out of code coaches, it's not a code violation.





Quote:
Originally Posted by Photobug View Post
My friend was not aware romex had 3 conductors and normal DC runs only needs two wires.
Your friend does not have the necessary knowledge/skills to design and build a safe, efficient, and working electrical system. He needs to get the "green book" (which is for houses but has a lot of basic info he will need) and spend a good amount of time learning the basics because once it's built he will be the one making repairs and needs to know what he's doing.



Quote:
Originally Posted by Photobug View Post
I think he was expecting to use Romex for all his wiring.
NNNNoooooooooooo It might save some money but the safety aspects alone make it a super bad idea.


Quote:
Originally Posted by Photobug View Post
Does anyone run romex for DC and just ignore the ground wire?
In an emergency to but never in the design and installation phases.


In the beginning there were two electrical systems competing to bring energy into the home. The DC system of Thomas Edison and the AC system of Nikola Tesla. The AC in our homes today is there because DC is more dangerous and less efficient than AC. It's fine for short runs and things like lights and fans but when you need some JUICE, to do some work, AC prevails because it can use smaller wires, produce less heat, and is more efficient.
However, new technological changes may well flip the switch (pun intended) back to DC.
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Old 07-27-2021, 06:01 PM   #14
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... On my rig I calculate the wire size for every wire, and use that size or better. B...
Good methodology. Also, larger conductors (of the same material) for a given load, will be more efficient thus saving those precious watts in the battery bank. Probably a miniscule factor in the short runs of a skoolie and all the other mechanisms of loss.
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Old 07-27-2021, 06:56 PM   #15
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Originally Posted by HamSkoolie View Post
Good methodology. Also, larger conductors (of the same material) for a given load, will be more efficient thus saving those precious watts in the battery bank. Probably a miniscule factor in the short runs of a skoolie and all the other mechanisms of loss.
[Geekin' out on conductor sizing]

Conductor: a 16' branch from the main panel to a subpanel on the other side of the bus carrying a max of 28A.

Wire Sizing: 2 x 12.9 x Amps x Length in feet/Acceptable voltage drop = CMils (from table https://ihiconnectors.com/AWG%20wire%20sizes.htm)

So 2 x 12/9 x 28 x 16/.24 [acceptable voltage drop] or 48,160 CMils. From the table, a #4 is a bit too small but #3 works. I happen to have a bunch of #2 so #2 stranded copper it is.

Fuse is based on the wire (max 95-115 Amps). I think I put a 50A circuit breaker on it.

THAT is how we avoid turning our buses into Roman Candles.
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Old 07-27-2021, 08:19 PM   #16
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I got back into this late and everything I've read others say, above, is spot on...and it's going to save your friend his bus and, perhaps, injury or death.

Romex, not in a conduit (except for short tubes where it passes through a bulkhead), has been permitted by the RVIA for some time for AC circuits, but never for DC since it's not rated for that. The RVIA follows the applicable portions of the National Electrical Code. I'm not clear on their stance on wire nuts in a bus or RV, though, but I'd stay away from those...or, if I *had* to use them inside a suitable junction box I'd make sure they were taped (in the proper direction) so they couldn't unscrew. But I'd go out of my way to avoid those.
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Old 07-27-2021, 09:12 PM   #17
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Thanks guys we are on the same page here. I want to do this right and would rather not install the A.C. circuit using Romex or install a $100 used fridge. I feel doing so is a false economy.

Using Romex is likely going to be more work than it's worth. And installing a cheap AC fridge will likely be way more power-intensive requiring a larger battery bank, solar bank and generator.

I just ordered wiring to finish up two sailboats.

I use this to calculate my wiring size. Circuit Wizard - Blue Sea Systems

and order my wires from here.

https://www.delcity.net/store/10-Gau...81402.h_181953
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Old 07-27-2021, 11:50 PM   #18
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Nice-I had been skeptical of marine sites because I started with a wire selection chart from some boat site that seriously derated the wires. Not sure which site now, just a lesson to check the source before relying on it.

This link seems to provide pretty good wire sizing and comments.
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Old 07-28-2021, 01:30 AM   #19
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Another chart

This is another chart from the same company. The one thing to recognize about a marine ampacity chart is there are two standards. 3 and 10 % voltage chart. Things like (off the top of my head may not be right) Navigation lights and communications radios, etc need to only have a 3% or less voltage drop. Your life depends on the nav lights are seen 2 miles away.

So you might see different numbers in a marine wiring chart to accommodate meeting these higher standards. You may not need this level of efficiency for a Skoolie build but the worst case scenario is you oversize the wires and ended up with a more efficient electrical system.

http://assets.bluesea.com/files/reso...on_chartlg.jpg

https://www.bluesea.com/resources/1437
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Old 08-10-2021, 01:10 AM   #20
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Quote:
Originally Posted by Photobug View Post
.
[edited for brevity]
.
...I just ordered wiring to finish up two sailboats.

I use this to calculate my wiring size. Circuit Wizard - Blue Sea Systems

and order my wires from here.

https://www.delcity.net/store/10-Gau...81402.h_181953
.
a)
Seconded on marine cable.
.
On our land-based rigs, I use marine cable exclusively.
The stuff I get is tinned over braided for extreme corrosion resistance.
.
Wire size:
Code might say '10-gauge for x feet to carry x amperage'.
I automatically go a size larger... in this example, I would spring for the bulk and weight of 8-gauge.
Why?
Our rig is constantly evolving, I have no way to predict future draws.
.
Draws:
As we grow and our rig evolves, we notice we use fewer appliances... reducing our electric needs.
.
For example, our chums offered us their barely-used expedition fridge, a SnoMaster 61qt.
They barely used it after the novelty wore thin.
Oddly, we fiddled with it for a couple-three weeks, then it joined the category of a NordicTrack clothes-rack in the corner of the bedroom.
.
I tend to think vibrations of a vehicle warrant braided cable instead of solid such as Romex 12/2.
A minor ability to absorb flexing could be the difference between a cool outlet and an outlet warmed by resistance.
.
b)
Lastly, I accept a significant reduction in flex/vibration absorption in my tinned cable compared to non-tinned or traditional automotive wire.
By compensating during the design phase, I believe I am probably good.
.
c)
Last:
Any words I write are the result of my experience, and may be the opposite of your needs.
If you do not know -- or if you do not trust your knowledge -- hire a professional.
Use the completed project for a few, and if you are satisfied, tip your professional generously.
.
d)
I mentioned investing in heavier cable than Code requires.
That weight quickly accumulates... particularly outside the center-of-mass such as the photovoltaic system on a roof.
.
Concluding that thought, I have no way to prove this, but I think a diesel pusher concentrates an enormous mass outside the center-of-mass, and has the potential to radically affect handling of a vehicle in motion.
As kids, we played crack-the-whip, a line of kids holding hands with one brave soul at the end of the line holding on for dear life.
.
A weight the size of a diesel engine plus auxiliary components such as radiator is a powerful motivator to follow Sir Isaac Newton's Laws (object in motion tends to stay in motion, etcetera)
Newton added a supplemental law after he retired to a BillionBuxBus conversion, following his dream of a life of relaxed travel:
* a diesel-pusher bus on a curving road tends to want to keep wagging that tail
.
And 'yes', weight as small as a few pounds of copper has an impact on vehicle handling, fuel mileage, and stopping ability.
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