I've purchased a Multiplus-II 24/3000/70, and the manual recommends a 300A fuse, but then only 50mm2 wire size - am I correct in thinking this would be undersized for a fuse of this size?
I'm also wondering if anyone has used a smaller fuse of say 175-200A?
I'd stick with the recommended size. The start current on the multiplus can be very high as its capacitors charge. If you do get a short, a 300A fuse will blow quickly.
Sorry if my questions are dumb, I'm quite new to this. Do you mean if I am not running the multi to full capacity then 50mm2 would be sufficient? The 50mm2 cables I am looking at have an amp rating of 246 at 30oC, and in all the wire size/maximum amperage charts I have seen 50mm2 is always under 300A.
On a good day the MP2 will only draw ~150A (continuous) to make its 3000W so your 50mm2 cable is safe. The fuse rating is, as @kevgermany points out, to deal with high start up currents of the MP2 etc. If you have a short circuit, this will exceed 300A very quickly and the fuse will blow (very quickly) and your cables will also be safe.
But no dumb questions, we all had to learn. So ask away.
