I'm gearing up to set up my first solar panel project and I've got a couple of questions about the electrical side of things. I plan to use two 200W 12V monocrystalline panels that will be connected in series as a single string. The specifications for the panels state that the short circuit current is 11.05A (ISC), and the optimum operating voltage is 19.2V (VMP). I want to make sure that I have a disconnect switch between the panels and the charge controller for safety. I'm unsure how to calculate the required amps for the disconnect switch. Would I multiply the short circuit current (11.05A) by 2 and then by 1.56, or just by 1.56? If I go with 11.05A x 1.56, that gives me 17.24A, which suggests I'd need a 20A breaker. But if I do 11.05A x 2 x 1.56, then I get 34.48A, meaning I'd need a 40A breaker. Can anyone clarify this for me?
3 Answers
Honestly, for just two panels, a disconnect switch isn't really necessary. But if you want to play it safe, just go with any breaker that’s rated for 20A or higher. You'll be fine there! Just remember, the current won’t exceed the rating at this size setup, so no need to overthink it too much!
Great question! The calculation really hinges on whether your panels are in series or parallel. Since you've got them in series, the current stays the same as one panel, which means you'd just use 11.05A for your calculations. You don't actually need to multiply by 2 because series circuits don’t add current. For your use case, a ~32A breaker would be a good choice, but honestly, many people skip the switch altogether for just two panels. It’s more about convenience than essential protection at that size.
You're on the right track! Since the panels are in series, your current stays the same at 11.05A, and any breaker rated at 20A+ should be more than sufficient. Just be cautious with that 1.56 factor; if it's not clear from your setup, it may not even apply here. Stick with what the specs say and you'll be good! No need to complicate it!
Thanks for the insight! I was just worried about safety with disconnection. Any thoughts on using a 30A switch with that setup?