Wander the West: Electrical Questions for a total rebuild - Wander the West

I'm helping a friend completely rebuild a 1980 Fleet. For now, there a couple of questions I need to figure out before we work on it this weekend. Any advice is appreciated.



First, what gauge wire to use from the battery to lights, sink, furnace, etc?

All we are doing this weekend is laying the wiring into the cabinet and ceiling so that we can finish the interior built. I'm wondering how to bring power from the battery to fuse panel (passing through a cutoff switch I suppose) and then go from the fuse panel to each device (lights, sink, 12v plug, furnace). Use 10gauge from battery to fuse panel? Any diagrams, suggestions or tips?

Thanks.

You should be able to find on-line wire size calculators. Look for a marine specific one because those will consider the ground wire's length as well. In campers this is an important thing, rarely is the chassis used for grounding, there's nearly always ground wire back to a buss or the battery and it's length is part of the circuit's length. I'm not convinced that those based on the NEC consider the ground wire's length. Ancor Marine used to publish a good one as part of their catalog, they may have it posted to their page.

The wire feeding the power panel will need to be big enough to support all of the loads at the same time with a little margin. If the panel is some distance away from the battery then you need a fuse or a breaker at the battery.

If solar is even remotely on the horizon I recommend reading White Dog's link in the "Multiple Charging Sources" thread as it is an eye opener. At least it was for me. Now would be a good time to address the wiring for that, even if the panels etc themselves are quite a ways off.

As mentioned you can do wire calculations for the various users. Below are the calcs I did for planning out some of my camper wiring. From doing so I can easily say for most all users if you're not trying to save a few pennies then running 14ga should cover your needs and then some in most cases. It isn't that much more costly, is a common size, etc. You could likely down size things to 16ga or 18ga depending and manufactures looking to minimize their costs do so, your call. If you've got any larger loads that aren't close to the battery then you may need to go larger.

Note on the below I'm under sizing the fuses based on my actual loads. I know what I wired with and know what I can upgrade them to if I'm looking to just protect the wiring (the true job of a fuse) but I'm going to start with them closer to the design loads actually on the circuits to take a conservative approach.

Excellent break-down of the circuits and their loads! If starting from scratch I would veer away from the typical RV type load panels that have a charger built in. Mine happens to be one of the worst possible examples, but in reading up on them none look very good about proper battery charging. I'll be disabling the charger in mine and going with an Iota 15A charger. Ordered with the IQ4 option it is a true 3 stage smart charger. (Having never been happy with general utility battery chargers I'm considering one of the Iota 30A units for the garage.)

<hijack> Pods, did you include the ground wire length in your truck to camper wire length? The numbers look screwy to me. I measured the actual wire run on mine and it came out to nearly 12' one way ('96 Club Cab Dodge 2500), so ~25' total circuit length. I used Ancor's 3% Voltage Drop chart to arrive at 6ga. for an arbitrary 80A (alt is ~100A, but with normal running loads.... ) figuring that I'd rarely ever push that hard on the camper battery. Not doubting, just concerned that you might be under-wired due to an over-sight when I've the impression it's contrary to your goals.
After reading the link that I mentioned above I'd go with 8ga. or even 6ga. on the solar feed. 20A x 17V (approx. solar panel voltage) = ~340W. That author has 345W fed thru 6ga. and he plans to re-wire up to 4ga. to further reduce the voltage drop. After reading his blog I understand and agree with why, though I'm not so sure that his needs match most of ours.</hijack>

The PD4045 is a stage charger (link if interested: http://www.progressi...ne_pd4000.html), I figured I'd give it a shot, not the end of the world to rework it later if needed since it'll be located on a panel right in front of the battery.

I used this calc http://www.nooutage.com/vdrop.htm and it asks for a one way distance so I've interpreted that (perhaps incorrectly) that the return let is already built in so we're talking similar distance of wiring I believe.

I'll put in a larger breaker but amps that high will never flow due to voltage drop, I was looking at what I'd get with something like a 2% drop for each wire gauge which still should be in the charging voltage. In the end that part will be what it'll be.

I think you misread on the solar, I have a 20' run not a 20amp load, its just a 100watt panel I was rounding up to 6amps for calculation purposes. Since I'm going with a PWM controller I'm figuring the voltage gets chopped to lower it anyways so there isn't as much value in running large gauge to maximize watts hitting the controller (after the controller its important) verse MPPT. That said I ended up running 3/4" conduit through my roof so I'll be able to pull larger gauge when the time comes to wire things if I want.

All the above stuff is still just on paper, I'm unfortunately not to that stage yet.

Thanks for all the (too much) information!

Different question: where does one get the distribution panel from? I'm having trouble finding one like that in my ATC.

brett13, on 23 June 2012 - 11:00 PM, said:

If you want just fuses look at bluesea.com, they've got a variety.