According to mm :
OK. I'm happy. It's been a long time but I thought one or two people
said it was bad at the time, and that 2 or 3 others have said it was
bad since then. Whoever did complain to me, it seemed like an
absolutist rule that didn't make sense. I'm glad it's not a rule
after all.

It better not be, because probably most people would be in violation
of it. The sum of the ampacities of branch breakers in a main panel
is _usually_ higher than the main feed breaker.

[IIRC, the breaker sum in our panel is 3 times the size of the main
breaker.]

BTW, slo-blo is only 5 or 10 seconds, right? It's more than 1/2
second like non-slo-blo, but no where near 30 seconds, is all of this
so?

I never timed one, but yeah, it takes a little while, but only a little.

That's what I thought.

Slo-blos are _specifically_ designed to ride out the startup current surge
of a motor - typically 3-5 times higher than the steady state amp rating
of the motor. If that takes more than 5-10 seconds (eg: the motor is stalled),
the fuse better blow or the wiring might do something real bad (eg: melt).

So, no, you don't want a slo-blow to take much longer than that.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.