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diy solar

Do I need a fuse here?

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I use a Midnite Solar PV Combiner that combines 4 series connected strings of panels into one paralleled output. Each string has its own fuse in the combiner box. The output goes to a 60 amp Epever charge controller, which also has a fuse. I'm not sure if the CC fuse protects the input or output. My question is, do I still need a fuse/breaker between the combiner output and the charge controller? Thanks for any advice.
 
YES ... sort of ... but not really ....

YES because anytime someone asks "do I need a fuse here" the best answer is always YES .. even without looking

SORT OF - because "IF" the fuse does fail then you can have a runaway and a second fuse down the line will stop that ....

NOT REALLY because each of the producers (panels) are already fused and the odds of a first fuse failing is very small ...

I would however have a CUTOFF switch between the combiner and the SCC ... for sure ...

SO from where I sit .. NO I would not put yet another fuse there ... but a switch ....
 
Schlagger said:
I use a Midnite Solar PV Combiner that combines 4 series connected strings of panels into one paralleled output. Each string has its own fuse in the combiner box. The output goes to a 60 amp Epever charge controller, which also has a fuse. I'm not sure if the CC fuse protects the input or output. My question is, do I still need a fuse/breaker between the combiner output and the charge controller? Thanks for any advice.
Click to expand...

Hey how do you like the 60A model of the EPSOLAR .. I have been playing with a 100A version and it fricking ROCKS .. the step up from 40A to 60A is huge in their design ...
 
Thanks ghostwriter, I'm going to squeeze a couple bluee sea breakers into the combiner box. Yours looks like the Ecoworthy, which is definitely less expensive. Mine was $400 from Northern Arizona Wind & Sun, prewired.
 
Good practice says all the cabling etc on the PV side should be rated to handle the full current the array can produce continuously, partly because typically you want to be able to get full power from the array. In what circumstance can any fuse here blow that will also offer protection to the cabling and/or SCC in a fault condition that doesn't involve the SCC getting some internal fault that manages to connect battery direct to the PV side combined with simultaneous fault appearing on the PV side that allows it pass destructive levels of battery current?

There isn't one.

If you are into over-panelling then potentially the SCC could have more current available at its input than it is design to cope with under fault conditions so a fuse could be useful in this circumstance.

An isolating switch of some type is always recommended, and in many cases required to get the installation certified.
 
gnubie said:
Good practice says all the cabling etc on the PV side should be rated to handle the full current the array can produce continuously, partly because typically you want to be able to get full power from the array. In what circumstance can any fuse here blow that will also offer protection to the cabling and/or SCC in a fault condition that doesn't involve the SCC getting some internal fault that manages to connect battery direct to the PV side combined with simultaneous fault appearing on the PV side that allows it pass destructive levels of battery current?

There isn't one.

If you are into over-panelling then potentially the SCC could have more current available at its input than it is design to cope with under fault conditions so a fuse could be useful in this circumstance.

An isolating switch of some type is always recommended, and in many cases required to get the installation certified.
Click to expand...

Do you see any issue with adding dc breakers in the combiner box? It's a tight squeeze, but I can do it. Rewiring inside would be a PITA. I most definitely am not over paneling. I always buy equpment rated for double what I plan on using. These CCs will never see more than 25 amps. Having the installation certified gave me a good belly laugh. There isn't anyone within 200 miles of me that co u ld do that. I live in a world without codes or permits of any kind-couldnt get one if I wanted to, so I just try to do things as safely as I can. Thank dog for this forum or I'd be screwed. Thanks for the reply.
 
These aren't the ones I would use, but ok to mount like this? I don't see any issues with it, but I'm not sure.

20200620_123809.jpg
 
If you can fit it in and have good clearance and accessibility that's fine IMO. I'm no engineer though. :)

*edit since post appeared above while I was typing*

I'm not a fan of putting the breakers there as the wiring above them makes access difficult. Are those things the real deal? So many fakes in that style. Although you probably already know, they need to be rated to break the PV Voc etc.
 
Last edited:
gnubie said:
If you can fit it in and have good clearance and accessibility that's fine IMO. I'm no engineer though. :)

*edit since post appeared above while I was typing*

I'm not a fan of putting the breakers there as the wiring above them makes access difficult. Are those things the real deal? So many fakes in that style. Although you probably already know, they need to be rated to break the PV Voc etc.
Click to expand...

No, these are crappy ones, I will get Eastman Buss in the same style and proper amperage. As long as it's safe, this is where I'd really prefer to put them. Otherwise I have to pull apart way too much stuff inside.
 
Actually, I could add a small disco box inside. That would be fairly easy. Maybe that's the ticket.
 
I already have some of these SquareD boxes. Do you know of a DC breaker I can use in these?

20200620_125337.jpg
 
Sorry no, not familiar with the mounting standards over there, ie how the breaker makes contact with the wiring, kept in place etc.
 
Thanks Gnubie. I really appreciate your time and knowledge. Have a great weekend.
 
@ghostwriter66 I would also add that the box I use is intended to run 2 charge controllers, so it will actually combine 8 strings total, 4 on each side, so that definitely drives the price up.
 
Ok, I got my Midnite Solar Big Baby enclosure, and 2 DC circuit breakers. Is anyone else concerned about how close together these terminals will be once installed? I only need 2, so I can put them on opposite ends, but I'm interested in smarter peoples' opinions.

20200624_122319.jpg
 
IMO that's plenty of clearance for the sort of voltages your arrays would be outputting, you'd just have to pay attention to the positioning of the wire connectors to keep them separated too.
 
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