Re: AC Hi Temp
Two things: first, the breaker has an inherent time delay that allows for startup inrush current. Ordinary fuses do not. As a result, non-time-delay fuses can be blown even when a 30A breaker would be adequate. (The fuse part # you mention appears to be a time-delay fuse.)
Originally Posted by dj1
The second thing is the heat: if the sun is shining directly on the disconnect during 100 degree weather, the ambient temperature of the fuses may be in excess of 160 degrees F. This may be enough heat to cause the fuse to fail at a lower current than normal.
The OP indicates that it's always the same fuse (of the pair) that blows; this could be attributed to a weak connection. The fuse block should be checked for corrosion, and the wire terminations in the disconnect should be checked for tightness and corrosion.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.