Roof junction/combiner box for RV?

System
System Posts: 2,511 admin
in General Solar Power Topics #1
I'm awaiting delivery of 4 135W panels and am trying to decide how I'm going to get the wiring through the roof of my camper and down to where the controller will be mounted. With how I plan to wire the panels (12v 540w array, 4 into 2 into 1 wiring) I will need a box with 4 knock-outs for weather-tight fittings. I'm aware of the box that amsolar sells but from pictures I've found I see that it has two holes on one side and the other two each by themselves on opposing sides. I would much rather all 4 holes on one side of the box, but have not been able to source such a creature.

Does anyone here have any leads for me?
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #2
    Re: Roof junction/combiner box for RV?

    It would help to know exactly which panels you have, as that might make a considerable difference.

    Aside from that, this is the most popular one we sell for smaller systems http://store.solar-electric.com/baby-box.html
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #3
    Re: Roof junction/combiner box for RV?
    WhiskeyTF wrote: »
    I'm awaiting delivery of 4 135W panels and am trying to decide how I'm going to get the wiring through the roof of my camper and down to where the controller will be mounted. With how I plan to wire the panels (12v 540w array, 4 into 2 into 1 wiring) I will need a box with 4 knock-outs for weather-tight fittings. I'm aware of the box that amsolar sells but from pictures I've found I see that it has two holes on one side and the other two each by themselves on opposing sides. I would much rather all 4 holes on one side of the box, but have not been able to source such a creature.

    Does anyone here have any leads for me?


    You could ask an electrician to make a couple of new holes for you.

    Any electrician worth his salt will have both hole-saws and slugbusters on his truck. Making new holes in boxes is an extremely common thing for electricians to do. Slugbusters are for stamped sheet metal only; for plastic or cast metal boxes new holes are made with hole-saws.

    http://www.toolup.com/greenlee/holemaking/metal/slugbuster-kits/manual-kits/

    Or...you could buy a small hole-saw for your own tool collection and DIY.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Re: Roof junction/combiner box for RV?

    Consider wiring the panels in series (less loss in the copper wire at high voltages) and use a MPPT controller.

    Look for an existing hole in the bed of the truck, and run the wire up thorough it, it wont leak till you are in a flood.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Roof junction/combiner box for RV?

    I'm using 4 Kyocera 135W panels on a BlueSky 3024iL. The specs of the panels and MPPT controller require that I wire them for 12V as I am maxing out it's capacity, if I wire for higher voltage I will exceed the listed specs. However the run from this box down to the controller will be ~5' of 6ga so I don't expect losses to be an issue.

    This just needs to be a weather-tight box to cover the hole through the camper roof as well as enclose the buss bars. I don't need any disconnects up there, just a cleaner version of the box I linked above, preferably plastic. That "baby box" is not a weather-tight enclosure. The amsolar box does not have room to make new holes, it is a very small box.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #6
    Re: Roof junction/combiner box for RV?

    Okay, so find a distributor who sells these and then buy a hole-saw:

    http://www.pactecenclosures.com/Plastic-Enclosures/OD-Series.html
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  • System2
    System2 Posts: 6,290 admin
    #7
    Re: Roof junction/combiner box for RV?

    Thanks, that's close but it really needs to have a removable cover for access if there's any future issues with the wiring. With the nature of RV rubber roofing, this box is going to be nearly permanently glued down to the substrate with sealant. I've been searching high and low for this box for months now throughout my planning without any luck. Maybe it really doesn't exist... :cry:

    I think part of my problem is I'm a bit anal/OCD about how cleanly things are wired. :blush: I'm a network guy by day and just got home from of full day worth of server rack cleanup. Seeing a big loop of poorly routed cable absolutely kills me, and I can just see a low hanging branch on a back road slipping under the loop and ripping my expensive panels to pieces. I'm fully capable of making something *work*, but I'd much rather use the proper solution if I can find it.
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  • System2
    System2 Posts: 6,290 admin
    #8
    Re: Roof junction/combiner box for RV?

    Ok, I'll bite.
    I just installed 4 BP125's on our older Airstream. I used a Pelican dry box as a junction box and hot glued 2 Bus bars in the bottom. I then used a Uni-bit drill bit, they look like a cone, to drill the holes. The bit makes nice work out of plastic and thin metal. Just use a smaller bit for a pilot hole first!
    I removed the rubber liner and made the holes, then put the liner back in and hot glued the bus bars to the bottom. When running the wire through, I used a thin sharp pocket knife to make an X in the rubber and ran the wire inside. When it was all said and done and fit like I wanted I used some clear silicone around the wire going in as I did not have any outdoor or waterproof grommets.
    I ran the 2 leads down through the fridge vent/exhaust port back to the charge controller at the rear.
    Oh yeah... I used a big square of Velcro on the roof to attach the box to. She hasn't budged yet!

    Regards,

    Erik

    Sales/Install
    Solar/Wind
    Alaska Wind Industries
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #9
    Re: Roof junction/combiner box for RV?
    WhiskeyTF wrote: »
    Seeing a big loop of poorly routed cable absolutely kills me

    Never, ever, look at my computer wires. Scanner, printers, monitors, speakers, 3 towers.... mice, keyboards, "wireless" routers, it's even worse then you thought.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • System2
    System2 Posts: 6,290 admin
    #10
    Re: Roof junction/combiner box for RV?

    Erik, excellent idea!!! I just happen to have a few spare 1200s here too. Unfortunately I don't have a roof vent for my refrigerator, mine is side vented because it's in the slide-out so I can't sneak wires down that way. If it did have that style vent I'd just use the box amsolar designed which fits right into the vent housing. So, I'll just have to put a hole in the bottom of the case for the wiring to run through the roof and down to the controller, no big deal.

    I found another solution that I will go with if the Pelican case idea doesn't work out. I totally forgot that these exist, and I think my local McLendon's hardware might even carry them.

    http://www.solarpanelstore.com/solar-power.wire.cable_grip.two-wire-cable-grip.info.2.html

    Thanks guys! :cool: I'll reward your time with some pics of the system as I build it.
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  • theno1katzman
    theno1katzman Registered Users Posts: 9 ✭
    #11
    Re: Roof junction/combiner box for RV?

    Hi,
    I was looking for a way to combine 4 panels and mount the connections to the roof. I needed to connect the positive and negative wires of the 4 panels inside a box in parallel to sit atop the van. I wanted them to connect and combine to bring the amps up to 22 amps for my charging needs. Then in order to run the cables through the top of the van, you need something like this:
    http://www.heyco.com/Liquid_Tight_Cordgrips/product.cfm?product=Liquid-Tight-Cordgrips-PG&section=Liquid_Tight_Cordgrips
    Not sure if other people sell these, this was what was recommended for me because their company is located in my state.
    Thanks for your post,
    Seth
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