Reply
 
Thread Tools Display Modes
 
Old 07-14-2019, 08:23 AM   #1
Bus Nut
 
ComfortEagle's Avatar
 
Join Date: Dec 2017
Location: Southern Maryland
Posts: 337
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: Cat 3208/Allison MT643
DIY Combiner Box

I used this generic junction box, a couple of these buss bars, and this bushing for the hole thru the roof...

The box will combine a 2S4P set of solar panels. So there will be 4 positive and 4 negative leads in, and one set coming into the bus. The buss bars are a bit too long, but once trimmed down they fit securely into the slots in the box. A hole had to be drilled into the bottom of the box to install the bushing for mounting thru the roof.




The split loom is for mock up only. I will be using a heavier duty and weather proof solution for the permanent install. Also once I clean up the roof I will be applying Dicor around box for an additional level of protection.


__________________
Rick <>< - Comfort Eagle (Bird Strike) - Solar/Batteries - Seat - Door - Dash - Mini Split - Fuse Box - Wood Stove
ComfortEagle is offline   Reply With Quote
Old 07-14-2019, 09:01 AM   #2
Bus Nut
 
TheHubbardBus's Avatar
 
Join Date: Apr 2019
Location: Hotzona
Posts: 269
Year: 2003
Coachwork: IC
Chassis: 3800
Engine: Navistar T444e
Rated Cap: 24
Looks good! Nice work.

One question: What prevents water from entering through the inlet?

FYI, We've used similar wire loom before for roof-mounted lighting on our truck, and before long (well... a couple years) it became brittle and cracked from UV & heat exposure. I'm pretty sure it was supposedly UV resistant - as I'd think that's something I'd have looked for. Just a heads-up. Don't know if there aren't other products out there that might give you both better life and a waterproof seal.
__________________
- Sharon & Jody
TheHubbardBus is offline   Reply With Quote
Old 07-14-2019, 09:39 AM   #3
Bus Nut
 
ComfortEagle's Avatar
 
Join Date: Dec 2017
Location: Southern Maryland
Posts: 337
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: Cat 3208/Allison MT643
Quote:
Originally Posted by TheHubbardBus View Post
Looks good! Nice work.

One question: What prevents water from entering through the inlet?

FYI, We've used similar wire loom before for roof-mounted lighting on our truck, and before long (well... a couple years) it became brittle and cracked from UV & heat exposure. I'm pretty sure it was supposedly UV resistant - as I'd think that's something I'd have looked for. Just a heads-up. Don't know if there aren't other products out there that might give you both better life and a waterproof seal.
Thank you for your feedback. As for your question regarding water intrusion, I haven't decided what route to take yet.

And again, the split loom is for mock up only. I will be using a heavier duty and weather proof solution for the permanent install.
ComfortEagle is offline   Reply With Quote
Old 07-14-2019, 11:15 AM   #4
Bus Nut
 
TheHubbardBus's Avatar
 
Join Date: Apr 2019
Location: Hotzona
Posts: 269
Year: 2003
Coachwork: IC
Chassis: 3800
Engine: Navistar T444e
Rated Cap: 24
Oh, gotcha.

Well, whatever you use in the place of the split-loom will hopefully kill both those birds with the same stone.

Don't know if you've seen this, but below the combiner-box on the following website (the $80 version of what you're building) there are water-tight strain-relief fittings. Probably rebranded versions of commonly-sourced items, but not sure. Appear to fit a standard e-box cutout (you'd obviously need a different weatherproof box w/o the female outlets).

Also, the video on that page shows their 10/2 weatherproof cable - which you can find elsewhere on the site - which they say is custom made for them (may or may not be). Either way, it appears to offer a really clean solution, and might be good additions to your project, either directly from them or the equivalent found elsewhere.

https://amsolar.com/rv-combiner-box/20-roof
__________________
- Sharon & Jody
TheHubbardBus is offline   Reply With Quote
Old 07-14-2019, 11:41 AM   #5
Bus Nut
 
Rivetboy's Avatar
 
Join Date: Jul 2017
Location: Huntington beach
Posts: 523
Year: 1991
Coachwork: Bluebird
Chassis: T/C 2000 28 foot Handy Bus
Engine: Cummins 5.9 Mechanical
Rated Cap: 2
Quote:
Originally Posted by ComfortEagle View Post
Thank you for your feedback. As for your question regarding water intrusion, I haven't decided what route to take yet.

And again, the split loom is for mock up only. I will be using a heavier duty and weather proof solution for the permanent install.
Sealtite 1/2" You will get sticker shock at the price of the connectors but ... Hopefully, your j-box has 1/2 fem threads.
Rivetboy is offline   Reply With Quote
Old 07-14-2019, 12:08 PM   #6
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 1,407
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
4 pos and 4 neg coming in on two terminal strips? .... I assume you are connecting the panels in parallel..
Are your individual solar panel wires capable of taking the short circuit of three parallel solar panels incase one gets shorted out?


How about your CC frying and a short circuit in one solar panel... shorting one panel thru the main breaker ??



Normally a combiner box has a fuse or breaker for each string.


Murphy never sleeps.
joeblack5 is offline   Reply With Quote
Old 07-14-2019, 05:52 PM   #7
Bus Nut
 
ComfortEagle's Avatar
 
Join Date: Dec 2017
Location: Southern Maryland
Posts: 337
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: Cat 3208/Allison MT643
Quote:
Originally Posted by joeblack5 View Post
Normally a combiner box has a fuse or breaker for each string.
Was going to fuse at the panels with these.

Here is the current plan; if it's gooned up, please let me know...
__________________
Rick <>< - Comfort Eagle (Bird Strike) - Solar/Batteries - Seat - Door - Dash - Mini Split - Fuse Box - Wood Stove
ComfortEagle is offline   Reply With Quote
Old 07-14-2019, 09:12 PM   #8
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 4,538
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
Looks slick.

With more than two parallel strings I would recommend overcurrent protection on each string at the combiner.

I have never attempted to build my own. I am a bit partial to the way it's done in the Midnite Solar combiner boxes.
PNW_Steve is offline   Reply With Quote
Old 07-14-2019, 09:29 PM   #9
Bus Crazy
 
joeblack5's Avatar
 
Join Date: Dec 2015
Location: pa
Posts: 1,407
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
That is good but still does not take care of murphy in full force.
The wire from your solar panel is probably 12 gauge. That limits the current to 20 Amps. Now if any of the wire is exposed before the inline fuse ( abrasion of insulation) to a short then how many amps can come out of your remaining solar panels or how many amps can come out of your fried CC.


In your diagram the CC shows 60 amp fuses in pos and neg. Only one is required, normally on the pos conducter assuming that you have your neg dc tied to ground.


So your inline fuses are acceptable if you would directly after your combiner box and / or the wire between the combiner box and the inline fuse can handle the largest short circuit current of all the other panels combined.


This is mostly done by integrating the breakers directly in the combiner box. Most likely also less expensive then the inline fuses.


I do like your clever use of lower cost materials to make your own combiner box but I do not think it is handy to have the inline fuses outside with your panels. And that is besides the potential of non current protected wire under worst case situation.


Johan
joeblack5 is offline   Reply With Quote
Old Yesterday, 06:21 AM   #10
Bus Nut
 
ComfortEagle's Avatar
 
Join Date: Dec 2017
Location: Southern Maryland
Posts: 337
Year: 1986
Coachwork: Gillig
Chassis: Phantom
Engine: Cat 3208/Allison MT643
BLUF:For the setup to be safe, the panel fuses need to be on/in/intergated into the combiner box, yes?

Quote:
Originally Posted by joeblack5 View Post
The wire from your solar panel is probably 12 gauge. That limits the current to 20 Amps. Now if any of the wire is exposed before the inline fuse ( abrasion of insulation) to a short then how many amps can come out of your remaining solar panels or how many amps can come out of your fried CC... So your inline fuses are acceptable if you would directly after your combiner box and / or the wire between the combiner box and the inline fuse can handle the largest short circuit current of all the other panels combined. This is mostly done by integrating the breakers directly in the combiner box. Most likely also less expensive then the inline fuses.
So I think I finally understand... Just to restate: the concern with fusing anywhere other than at the combiner box is that even if a fuse pops at the panel, the possibility still exists for an unprotected short between the combiner box and the blown fuse (or a non-blown fuse for that matter).

Quote:
Originally Posted by joeblack5 View Post
In your diagram the CC shows 60 amp fuses in pos and neg. Only one is required, normally on the pos conducter assuming that you have your neg dc tied to ground.
I had read that a breaker on both sides, while not required, is a nice to have in terms of ability to easily and fully disconnect the panels from the rest of the system.

Quote:
Originally Posted by joeblack5 View Post
...Most likely also less expensive then the inline fuses... I do like your clever use of lower cost materials to make your own combiner box but I do not think it is handy to have the inline fuses outside with your panels...
I disagree that it would be less expensive, however, it is not only about cost...
__________________
Rick <>< - Comfort Eagle (Bird Strike) - Solar/Batteries - Seat - Door - Dash - Mini Split - Fuse Box - Wood Stove
ComfortEagle is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 06:04 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.