proper fusing for 300w in parallel and question about renogy kit contents

[havesomejoe]

Hi all,

I recently started installing a 300 watt renogy kit that I bought last year and am realizing that they may have designed the kit assuming you would wire the panels in series rather than in parallel. They provided a 10 amp mc4 inline fuse but I'm thinking that has no use so I'm trying to figure out what to replace it with and if my plans are going to be safe.

I have attached a simple graphic showing the kit with some question marks.

- They supplied 20 ft of 10awg wire but I believe I can trim off about 4 feet so it would be closer to 16ft when installed. I've looked at various charts and it seems like it should be okay to carry the max ~25 amps.

- The mc4 3-way branch connectors are rated at 30 amps.

- I want to add a breaker near the charge controller so I can disconnect it at will. I ordered a 40 amp one as that would be 1.5x rounded up from the 25 amps.

- What I'm really not sure about is the fusing near the panels. The 10amp one they gave me surely cannot work unless I put it only on one panel before the branch connector, then I'd need to buy two more for the other two panels. My other thought would be to put one after the branch connector but I could only find a 30amp inline mc4. Would that be a good idea? Wouldn't it be odd to have a 30amp fuse at one end and the 40amp breaker at the other since the fuse would always pop first? If the branch connector is rated at 30amps it seems like that would end up acting as a fuse as well...

Does this seem safe or do I need to rethink it?

 

[Craig]

What I do not like is that your breaker will never trip but that is ok if you are just using it as a switch. I would use the one 30A inline fuse . You could get a 32 Amp breaker and a 35 amp fuse.

I actually have a similar situation with multiple strings combining I opted to put breakers on each of 2 strings and another breaker after the strings combined plus a breaker at the control room as panels are roughly 200 feet away. This way I can also turn off half my array if necessary for testing etc..

 

[havesomejoe]

What I do not like is that your breaker will never trip but that is ok if you are just using it as a switch. I would use the one 30A inline fuse . You could get a 32 Amp breaker and a 35 amp fuse.

What is your reasoning behind the different sizings? What if I used a 30a breaker and 30a fuse?

 

[Craig]

Mist DC breakers I have seen come in 32 Amp fuses usually use round numbers. And I wanted the breaker to trip before fuse if possible so I don't blow out costly fuses when I make a dumb mistake.