I'm setting up my first off-grid solar system and need some guidance on the right wire and fuse sizes to ensure everything runs safely and efficiently. My system will be a 48V setup.
Here's what I've got so far:
- For the solar array to the MPPT controller, I'm planning to use 8 AWG wire with a 35A breaker, given my four 535W Jinko panels which will be wired in a 2s2p configuration. I calculated around 28A and 113V load over a 25ft run, so that seems right.
- For the connection from the MPPT to the batteries, which is an 80A MPPT and two 48V 100Ah batteries in parallel, I figured on needing 8 AWG wire and an 85A breaker since the load should be about 70A for a 2ft run.
- Lastly, from the batteries to my inverter, using a 4000W inverter, I'll need a 2 AWG wire and a 200A fuse given the load of 166A.
Can anyone check my math? I want to make sure I don't mess anything up.
Also, can someone explain when to use a circuit breaker vs. a fuse? And should I install a disconnect switch anywhere in this system? Thank you!
2 Answers
For your MPPT to battery connection, 8 AWG is actually on the thinner side for 70 amps, so you might want to bump that up to a thicker gauge like 6 AWG, just to avoid overheating. As for the circuit breaker vs. fuse question, circuit breakers can be reset after tripping, which is a big plus for ease of use, while fuses need to be replaced. I’d suggest using breakers where you can, but fuses can be fine too, especially in simpler setups. And yeah, definitely consider adding a disconnect switch! It's a handy way to ensure safety while maintenance or troubleshooting your system.
Hey there! It’s great that you're doing your research before diving in. For your setup, while 8 AWG can handle a 35 amp load perfectly, it does get a bit sketchy with 70 amps. You might want to consider going up to a 6 AWG for that part to be on the safe side, especially since wires can heat up at higher loads. Just to be safe, check the ampacity charts for your wire size based on the insulation type too.
For your last section, going with 2 AWG and a 200A fuse looks solid, so nice job there! Make sure you include some extra space in your calculations for future upgrades if possible. Always better to have a little buffer!
Exactly! Plus, keep in mind that under different conditions (like temperature), your wire's capacity can change too. Always better to err on the side of caution.
Yeah, disconnect switches are smart! They give you peace of mind when you need to work on your system without risking a shock.