Combining solar panels with a busbar - Advice needed

[theHouserHouse]

We're serious newbies working on putting solar on our travel trailer and need some guidance. Right now we are trying to connect our eight 100w solar panels together.
They are set up 2 together in series
Each series has a 15amp in-line fuse on the positive wire
Then the 4 sets are going to be connected together in parallel at busbars in a waterproof box up on the roof of the trailer.
That's 4 positive and 4 negative 10g wires coming in to the box
One positive and 1 negative 6g wire will go from the box down into the camper. On the positive wire there will be a 30amp fuse. The wires then go on to the solar charge controller
We're struggling with picking out the correct busbars and corresponding ring terminal connectors.
We have a 5.5x7.5" waterproof box that has 10 port holes. It looks like it will hold two 4" busbars and the wires nicely, I think? We have to account for the gland entries (or nipples) that need to be added on to the box as well.

I forgot to mention the volts and amps of our array...
Each set in series 41.2 volts and 4.85 amps
Four sets in parallel 41.2 volts and 19.4 amps

Any thoughts on the busbars and terminal connectors we should be buying?

 

[snoobler]

There are combiner boxes designed for exactly what you're doing. Here's a DIY version:

Your fusing sounds good.

 

[Zil]

Obvious you need two bus bars. One positive and one negative. They could be on the same base or not. They each need enough screws to take the number of panel wires and one more for the combined cable into the van. You do not need the last fuse before the CC. Use a switch so you can disconnect the panels.

 

[theHouserHouse]

There are combiner boxes designed for exactly what you're doing. Here's a DIY version:

Your fusing sounds good.

Thanks. We checked this out and liked it but cannot get the parts until November. :/ A local friend just found this combiner box and circut breakers for RV solar. It looks like it will be easier than DIY. Fingers crossed.

Amazon.com

 

[theHouserHouse]

Obvious you need two bus bars. One positive and one negative. They could be on the same base or not. They each need enough screws to take the number of panel wires and one more for the combined cable into the van. You do not need the last fuse before the CC. Use a switch so you can disconnect the panels.

Yes, our problem was finding the correct parts. Nothing local and we were not finding the right size busbars for our setup on Amazon. I hope the ready made combiner box our friend found will work out.

 

[snoobler]

This was is a little cheaper and has a perimeter seal:

https://www.amazon.com/ECO-WORTHY-Combiner-Breakers-Lightning-Arrester/dp/B07F5HDP2W

The other one only had a visible rubber seal on the 3 non-hinged sides.

 

[theHouserHouse]

This was is a little cheaper and has a perimeter seal:

https://www.amazon.com/ECO-WORTHY-Combiner-Breakers-Lightning-Arrester/dp/B07F5HDP2W

The other one only had a visible rubber seal on the 3 non-hinged sides.

Our setup is too large for the cheaper unit.

 

[snoobler]

You said you have 4 strings of two. Why won't it work?

 

[Zil]

Do not go cheap. Go quality. As paralleled panels do need fuses, I built a combiner box using this fuse block from Blue Sea. It handles the 4 parallel positives. They also have a 8 circuit block. The negatives are just fastened together as a common negative. https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits

 

[theHouserHouse]

You said you have 4 strings of two. Why won't it work?

We have 800 watts of panels, the smaller box is not rated for that many watts.

Do not go cheap. Go quality. As paralleled panels do need fuses, I built a combiner box using this fuse block from Blue Sea. It handles the 4 parallel positives. They also have a 8 circuit block. The negatives are just fastened together as a common negative. https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits

Thanks for the link. I will check this out. I'm not really excited about the Eco-Worthy 6-string combiner box. Our friends ordered it for us without our input. I'd rather build our own.
One question - we have 15 amp fuses in-line on the positive wire for each set of panels in series. Once the 4 sets of series are combined in parallel, there will be a 30 amp fuse. So, wouldn't the fuses in this 4-circut fuse block be redundant? I don't think that matters, just asking.

 

[snoobler]

We have 800 watts of panels, the smaller box is not rated for that many watts.

Thanks for the link. I will check this out. I'm not really excited about the Eco-Worthy 6-string combiner box. Our friends ordered it for us without our input. I'd rather build our own.
One question - we have 15 amp fuses in-line on the positive wire for each set of panels in series. Once the 4 sets of series are combined in parallel, there will be a 30 amp fuse. So, wouldn't the fuses in this 4-circut fuse block be redundant? I don't think that matters, just asking.

Only 1 fuse/breaker is needed per conductor. 1 for each series string and 1 for the conductors between the combiner box and the charge controller.

I prefer breakers as it allows me to isolate strings easily.

 

[Zil]

Fusing solar panels. Fuses protect wires. Fuses effect voltage drop. Solar panels are limited power supplies. If we short the panel wires together the amperes will be limited by the solar panel maximum output. Panels in series, 4.5 amps will never hurt a 10 awg cable. No fuse needed. Panels in parallel, if one panel-set has a failure, the other three panel-sets can feed 15 amperes into the failure. While that can not stress the 10 awg cable, there are lighter circuits inside the shorted panel-set that could be a problem. But beside that. If one panel-set shorts the other panel-sets, the whole system goes down. No more charge until you maybe find the problem. If each panel-set has a 10 or 12 amp fuse before feeding the combined cable to the CC. 15 amp short in one panel pops the fuse. The remaining panels continue to supply the CC. The 6 awg from combiner connections will never be stressed by the amperes from the panels up to over 100 amps. But each fuse provides more voltage drop. Voltage drop is very very bad in solar charging system. It is good to disconnect panels from CC. Use a switch that will have very low voltage drop. https://www.bluesea.com/products/6004/Single_Circuit_ON-OFF_with_Locking_Key_-_Red
On the output side of the CC. You need a fuse at the battery positive terminal or buss bar if that is the connection point of the CC. Size the fuse to protect the wire. Fuse is not sized to the CC except that the fuse is not too small.

 

[chrisski]

I bought a midnite solar combiner box, which is great, but prior to that I had plan on using a 10 Gang Box Connector (https://www.amazon.com/gp/product/B01BSPR4PO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) to make a combiner, which I was going to place in a 9" X 6" junction box (https://www.amazon.com/gp/product/B00HG7FM26/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) .

For the breakers with for each string of parallel panels were going to be placed in a separate 9" X 6" box and then sent to the gang box.

What stopped me from this is the wire size I needed to run from my combiner down to my SCC. the 15' or so of 36 amps ended up requiring thicker wire than I wanted to use.

The Midnite solar combiner box is not designed to lay flat on an RV roof, but I got the 10 Gang Box idea from RV with Tito https://www.rvwithtito.com/. He's got some great YouTube Videos.

 

[theHouserHouse]

Time to move but wthe panels are not connected to anything yet.

We are going to keep looking at these options, but right now it's time to get outta Dodge. Temperatures are dropping here in Iowa and we need to move on. We'll be traveling for about a week. Our panels are installed on the roof and not connected to anything. We've had them covered with cardboard since mounting while trying to sort this out. Figure we can't drive with the cardboard up there. LoL The sets are connected in series and the rest of the wires are capped with mc4 dust caps. Any suggestions? Is it safe to uncover the panels for a week of travel?

 

[snoobler]

Uncovering the panels is fine. Touching the leads to your tongue? That's a bad idea.

If you really care, break the series connections, and you just have a bunch of low voltage panels up there.

 

[theHouserHouse]

Uncovering the panels is fine. Touching the leads to your tongue? That's a bad idea.

If you really care, break the series connections, and you just have a bunch of low voltage panels up there.

I will pick up some more dust caps and break the series before we go. Thanks

 

[snoobler]

sandwich bags and rubber bands.

 

[theHouserHouse]

Should I get these grounded before we leave too?

 

[snoobler]

Nope. Your entire RV is insulated from ground via the tires.

 

[Gould]

Do not go cheap. Go quality. As paralleled panels do need fuses, I built a combiner box using this fuse block from Blue Sea. It handles the 4 parallel positives. They also have a 8 circuit block. The negatives are just fastened together as a common negative. https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits

Resurrecting this post as I’m at the same point in my build. The circuit block has a rating of 32v, is that for the entire bus or per connection?