Would it be a bad idea to use a fuse block like below as a way to combine the wiring from my panels (parallel). Of course it would have to be mounted in a waterproof container but it would be handy if I chose to fuse each individual leg (I know that may not be strictly necessary but I'm a belt and suspenders kind of guy).The one thing i don't like is that it would need ring terminals on the wires, not sure how much resistance they would add.thoughts?

Sounds fine. Panels don't need fuses. There are no pants.

hedge wrote:Would it be a bad idea to use a fuse block like below as a way to combine the wiring from my panels (parallel). Of course it would have to be mounted in a waterproof container but it would be handy if I chose to fuse each individual leg (I know that may not be strictly necessary but I'm a belt and suspenders kind of guy).The one thing i don't like is that it would need ring terminals on the wires, not sure how much resistance they would add.thoughts?I agree with 2oldman ... should work fine, but overkill. Something like this still provides convienence, without the fuss of fuses:http://www.ceshowroom.com/ProductDetails.asp?ProductCode=CWR20224My thinking is, although designed for marine, all those fuse connections provide more places for corrosion to set in and rob you of precious solar power. You only need one inline fuse, before the charge controller, to protect the feed in from the roof.I would not use a waterproof box, as it will trap humidity inside, aiding corrosion. Just use a plain junction box, so any water that makes it in will also make it out. Mount it such that if water pools on the roof, it will not pool inside the junction box.

With proper crimp the spade terminal should add no measurable resistance.Only 3+ panels in parallel could ever need a fuse.

thanks. I'm kind of having a hard time finding the parts I need up here. I happen to have the fuse box already was why I was thinking of using it. I'd have a max of 4 100w panels.

hedge wrote:thanks. I'm kind of having a hard time finding the parts I need up here. I happen to have the fuse box already was why I was thinking of using it. I'd have a max of 4 100w panels.You don't really need any "parts" ... just brass or stainless steel bolt, nuts and some washers. Two "sets", one for positive, one for negative.Crimp ring terminals onto your solar panel feeds, then stack them together on the bolt along with the feed to your controller, add a washer and tighten down the nut. You could drill the bolts through a piece of plastic or wood first, so they don't flop around or risk touching each other. Finish with spray paint or use battery terminal coating to keep corrosion at bay.

Fuse block used in reverse as combiner? | Good Sam Community

17 Replies

hedge
Explorer
Jul 20, 2016
GordonThree wrote:
wa8yxm wrote:
I see no problems other than the additional resistance of the fuses. which in that configuration is not going to be much.

Also heaven forbid a panel shorts out.. Might just save the rest of 'em if the fuse is properly sized.

If a panel shorts out, how could that damage the other panels?

The only way I could see the fuses "saving" the panels at all is if somehow a very high voltage was applied to the wiring from the charge controller, maybe it got connected to shore power or something.

From doing a bit of research, it seems it would be possible for the other panels to try push their current through the bad panel, seems to only be an issue if you have 3+ panels. I'm just learning this stuff so I'm just providing the link.

https://www.civicsolar.com/support/installer/articles/when-fuse-when-not-fuse
RedRocket204
Explorer
Jul 20, 2016
GordonThree wrote:
I would not use a waterproof box, as it will trap humidity inside, aiding corrosion. Just use a plain junction box, so any water that makes it in will also make it out. Mount it such that if water pools on the roof, it will not pool inside the junction box.

Just a FYI on those Blue Sea Systems fuse boxes... yes they are designed for marine applications but no, they do not trap water inside. I have the first Blue Sea Systems fuse box listed in this thread on my atv and can tell you that clear top is not water tight, water proof or anything of the sorts so no way for water to be trapped. Very good quality on the Blue Sea Systems fuse box I have.
red31
Explorer
Jul 20, 2016
Does array max Isc exceed continuous current rating of conductor selected?

4 panels minus 1 = 3, 3 X Isc (~5.5A) = 16.5A, 16.5A exceed wire rating?

If no, no PV fuse needed
GordonThree
Explorer
Jul 20, 2016
wa8yxm wrote:
I see no problems other than the additional resistance of the fuses. which in that configuration is not going to be much.

Also heaven forbid a panel shorts out.. Might just save the rest of 'em if the fuse is properly sized.

If a panel shorts out, how could that damage the other panels?

The only way I could see the fuses "saving" the panels at all is if somehow a very high voltage was applied to the wiring from the charge controller, maybe it got connected to shore power or something.
wa8yxm
Explorer III
Jul 20, 2016
I see no problems other than the additional resistance of the fuses. which in that configuration is not going to be much.

Also heaven forbid a panel shorts out.. Might just save the rest of 'em if the fuse is properly sized.
All_I_could_aff
Explorer
Jul 20, 2016
smkettner wrote:
Not much going on with solar at night...

The man speaks the truth
westend
Explorer
Jul 20, 2016
I made my own combiner box from off-the-shelf parts. A plastic exterior rated box with a gasket and two lug strips pulled from an abandoned load center. The run to the controller is interrupted by a manual resettable circuit breaker. The function of the circuit breaker is to interrupt power from the module so that I can work during the day, downstream, without any current present.

Here is the combiner box, an LB. I have the wires in conduit to the controller location:

Watertight box entry:

Here is the manual breaker used as a switch:
Cooper-Bussmann manual circuit breaker
Searching_Ut
Explorer
Jul 19, 2016
The setup you're describing is how I built my combiner box. Fuse panel that holds 6 fuses put into plastic junction box with a bus bar for the negative connections, waterproof strain reliefs for the wires coming in. I currently have 5 100 watt solar panels combining in my junction box, but recently ordered a 6th panel which I'll be installing when I get the chance.

The way solar panels work, if you short the output wiring out, the current flow doesn't increase enough to where a fuse would be likely to blow anyway. On the other hand, should power feed back through the panel for some reason the fuse could be of benefit to prevent a feed from the other panels in parallel, or the battery. I debated going without fuses, but after asking for recommendations on these forums decided to go with my initial instincts of adding them in.
Chris_Bryant
Explorer II
Jul 19, 2016
The fuses would add more resistance than a ring terminal.
doughere
Explorer
Jul 19, 2016
Kinda overkill, but I think its a great idea. Keeps everything nice and neat, and if you ever need to troubleshoot, makes it easy.

Doug