Which type of fuse/breaker?

[Bluedog225]

Good morning,

At what point do I need to graduate up to a better class of fuse or breaker?

I have three 100 watt panels in parallel. So roughly 14 volts, 300 watts, and about 21 amps.

And a 30A victron PWM controller. 12 volt battery.

Can I use a 30 amp blade type fuse for both the panel to controller feed and between the controller and battery?

I don‘t want to pull an arc when I pull a fuse but don’t know what voltage/amps at which that starts to be an issue.

Thanks

 

[OffGridInTheCity]

I like/use Midnite Solar 'DC' breakers like this - https://www.amazon.com/MidNite-Sola...+Solar+25a+breaker&qid=1638464073&s=hi&sr=1-3
They're not too expensive and snap onto a DIN rail.

Midnite now has a 'baby box' that is not that bad a price to hold several of these - https://www.amazon.com/MIDNITE-SOLA...+Solar+Breaker+Box&qid=1638464157&s=hi&sr=1-3

Might be overkill - just sharing what I use as you might be ready or might grow in the future

 

[740GLE]

Are you using a combiner box of some sort for parallel the panels or bus bar?

30a from SCC to battery is fine.

I also second the midnite solar DC brks with a combiner box, 3x 10a bkrs, one per panel, and one 30a bkr to the SCC. it makes for a nice clean install and easy to isolate for troubleshooting.

 

[Bluedog225]

Right now, I have a renogy 3:1 mc4 combiner and and single 10 gauge wire directly into the victron controller. I got it roughed in and need to clean it up as a semi-permanent installation.

edit-and thanks, I’ll check out the midnight solar.

 

[Zil]

The CC to battery must have a fuse at the battery positive. That could be a BusBar or it could be the pos battery terminal. That fuse must be sized to protect the wire that connects the CC to the battery. I think a 30amp blade fuse is not a good choice. This would be better; https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

How I combined my parallel panels. Each panel has a short circuit 10 amperes. If one panel failed the other two would short to that panel, 20 amperes. I use a BlueSea 4 fuse panel for the combining positive panel wires. Each has a 15 ampere fuse. If one panel fails that panels fuse will open allowing the other two panels to charge my battery. This; https://www.bluesea.com/products/5045/ST_Blade_Compact_Fuse_Blocks_-_4_Circuits

 

[HRTKD]

Some of us are using a circuit breaker between the solar panels and the solar charge controller. It provides overcurrent protection but also gives you a handy way to switch off PV power going into the solar charge controller. I have my dual pole circuit breakers mounted on a DIN rail.

I use Cooper Eaton Bussmann Series 187 Surface-Mount Marine-Rated Circuit Breakers on the output side of the solar charge controller. This is also a handy way to switch off power, but it's mainly there for the overcurrent protection.

If you go with a circuit breaker, be sure you're using ones that are specifically designed for DC circuits.

 

[Bluedog225]

Thanks all. Jim-you say on the output side of the controller. Do you mean between the controller and the battery? Thanks

 

[HRTKD]

Thanks all. Jim-you say on the output side of the controller. Do you mean between the controller and the battery? Thanks

Correct.

 

[Bluedog225]

Thanks. If you don’t mind explaining, what situation would result in too much current between the battery and controller? And in a similar vein, why would you need to turn off power to the controller?

 

[HRTKD]

Thanks. If you don’t mind explaining, what situation would result in too much current between the battery and controller? And in a similar vein, why would you need to turn off power to the controller?

If the controller freaks out (very technical term there) you could get more than the rated amps. Highly unlikely, but why take the chance.

I have two Victron MPPT 100/50 controllers. One for the roof, which is always on, and one for the ground deployed panels, which are rarely connected. I flip the breaker to the second one so that it doesn't draw any unnecessary juice from the battery.

 

[Bluedog225]

Got it. Thanks!

 

[OffGridInTheCity]

Thanks. If you don’t mind explaining, what situation would result in too much current between the battery and controller? And in a similar vein, why would you need to turn off power to the controller?

I have circuit breakers near the contollers on the PV side and at the battery buss-bar control box.

PV Side - this turns off incoming PV power at the controllers, so I don't have to go 150ft outside to the arrays and turn off the breakers at the combiner boxes. Its a convenience + safety, they are 'right there' so I can be safe working on the controllers.
There's 1 circuit breaker for charge controller. Each circuit can have up to 130v and up to 50a... dangerous levels of power. Good to turn them off before working on the Charge Controllers.


Battery Side - this breaks output between the controllers and the battery sub-system... so I can work on the shunts, the battery, everything in the battery control box safely.
This is up to 240a @ up to 58.8v - dangerous levels of power.


It's important (for me) to do disconnect both sides (PV and Battery) because the Midnite Charge Controllers are energized from either side! Need to isolate both to work safely.

Also, I can isolate the Charge Controllers to work on them and the rest will continue - e.g. battery + inverters -> powering-things. All just flipping a few circuit breakers

 

[Bluedog225]

That makes sense. I was thinking of shorts and fires. Got it. And thanks!

 

[Browneye]

The option to shut things down easily makes any maintenance or troubleshooting much easier.
NEC says you need a PV cutoff now anyway.

Here’s a good resource on the subject:

 

[Bluedog225]

I have circuit breakers near the contollers on the PV side and at the battery buss-bar control box.

PV Side - this turns off incoming PV power at the controllers, so I don't have to go 150ft outside to the arrays and turn off the breakers at the combiner boxes. Its a convenience + safety, they are 'right there' so I can be safe working on the controllers.
There's 1 circuit breaker for charge controller. Each circuit can have up to 130v and up to 50a... dangerous levels of power. Good to turn them off before working on the Charge Controllers.
View attachment 74251

Battery Side - this breaks output between the controllers and the battery sub-system... so I can work on the shunts, the battery, everything in the battery control box safely.
This is up to 240a @ up to 58.8v - dangerous levels of power.
View attachment 74250

It's important (for me) to do disconnect both sides (PV and Battery) because the Midnite Charge Controllers are energized from either side! Need to isolate both to work safely.

Also, I can isolate the Charge Controllers to work on them and the rest will continue - e.g. battery + inverters -> powering-things. All just flipping a few circuit breakers

And wow! That’s quite a battery setup. How many kwh?