These breakers, made by CBI in South Africa, are Hydraulic-Magnetic, not Thermal-Magnetic. Ultimately it doesn't make much difference as long as they work and carry a UL489 listing as a branch circuit breaker, and it's true that H-M breakers are always rated for 100%. That'
s because the breakers don't change tripping characteristics when hot. The common H-M breaker used in the US has been Heineman for years (now owned by Eaton I think). The only issues with H-M breakers are that they tended to be more expensive, they must be mounted vertically because the plunger mechanism can be influenced by gravity, and the trip times vary with LOWER temperature more than a basic T-M breaker will. That's because the silicon oil used to dampen the magnetic trips will change viscosity when really cold, so the breaker may take longer to trip. The up side to that is that they do NOT nuisance trip when hot, so in a lot of applications where heat is a potential issue, people tend to use them instead of the cheaper T-M breakers.
However, ALL UL listed
breakers are tested for use at 100% current, the "80% rating" is kind of an urban myth. UL489 testing of the breakers themselves says absolutely NOTHING about only loading them to 80%, the continuous rating of a UL489 listed branch circuit breaker is officially 100% of the rating under the breaker test procedure,
which is all by itself in free air. The so-called "80% rule" for a breaker is based on how they are MOUNTED and terminated as part of a SYSTEM that includes the box you put them in. If you want to USE the breakers at 100% rated current continuously, the way they are mounted and wired is part of
that listing.
So here's the kind of "iffy" part of this; If you look carefully, that web page for Midnight Solar says the following, parsed out with my comments in red;
Note: Branch circuit rated 489A
True; the breakers themselves are UL489 listed.
All MidNite circuit breakers are rated for 100% continuous duty. MidNite’s breakers are rated to break the full rated load at the rated voltage repeatedly, with NO DAMAGE. Always use a properly sized breaker for disconnecting.
Nothing about this is incorrect, just misleading. ALL UL489 listed BREAKERS can make this statement as it is worded.
All MidNite circuit breakers can be used at 100% rated current when mounted in a MidNite enclosure.
Ah, THERE'S the rub right there. ONLY in THEIR enclosures. Then if you look a little deeper into that, their enclosure packages are NOT listed by UL, they are listed by ETL. I know that ETL is a perfectly acceptable NRTL, but I also know from direct experience that it is a lot easier to get something through them than it is with UL. I'm not saying anyone deliberately pulled a Volkswagon here, but it's possible that in the listing process with ETL, the Midnite Solar people may not have told them the complete story as to how many breakers might be in the box, how close they would be to each other, what size and type of wire would be used in the field, etc. etc. etc., and the ETL people may not have known to question it the way UL would have, who deals with that issue day in and day out. Even if I'm wrong about that, the only boxes they sell hold a maximum of 4 breakers, so not too hard to get that to pass.
Don't get me wrong here, what they are saying it likely all true, but it may not mean what you THINK it means.