Understand that DC breakers/isolators perform different functions/are different (arc supression, load breaking→no switching under load etc. I’m interested in views of whether there should be both between panel(s) and charge controller. I’m probably overthinking it (and read around too much!). It’s my first system and want to get it right (at least from the safety side). I’m not dealing with high voltage (<50V). I have seen many ONLY using switches, and many ONLY using double-pole DC breakers. Also seen a few recommend both (is this mainly in a grid-tied commercial setup?). What’s standard practice for DIY/off-grid setups?
The short answer is you should design the system both for your convenience and for safety.
The use of over-current protection devices (fuses or breakers) between the solar panels and the solar charge controllers is generally only required when you have 3 or more series strings in parallel. This is to protect a string if it develops an internal short, where the other two strings would dump all of their power through it.
The reason that the protection isn’t required for one or two strings in parallel is that solar panels are current limited, specifically to the Isc value on the label. The label also has a max fuse rating in amps that should be followed when adding a fuse or breaker.
However, for convenience, having a disconnect switch is a good idea when you need to isolate problems or service the solar array.
Some people use DC breakers to act as a disconnect because they are inexpensive.
If you use cheap DC breakers, be aware that there are lots of reports of them melting and failing.
This is usually due to the terminals coming loose over time, and in general low quality.
Hi Rick, while i’m aware of everything you detail I do appreciate you taking the time to respond. I suppose I was looking for a good reason to install only one or both (breaker/switch) - for, as you point out, both safety and convenience. People are understandably often aligned towards one or the other because it is ‘what they’ve installed’. Thanks again for your thoughts.
Personally I only install a breaker and use that for both: To protect the CC and also use it as an isolator - kill two birds with one stone, so to speak. Is there a problem with that?
Thanks Fideri. Yes i was leaning towards a good quality DC breaker as switches don’t provide over current protection and generally shouldn’t be used under load. But of course, i’m completely open to being convinced otherwise! Much of the ‘educational’ material around tends to be towards selling a product rather than good pragmatic reasoning… Switches/breakers do serve different purposes, and that’s really the reason for my question. In larger (and grid-connected setups) I can definitely see the need/use of both, but for a shed setup with only 400w (<50v) I wanted to raise the question.