I did an inspection a few days ago, and this place had a 100 amp fusebox. It had 30 amp fuse on 20 amp rated wiring. The reason for this according to the homeowner is because of the window air conditioner would blow the fuse. I know that the start up winding draws more amps at first but enough to blow a fuse? Does this sound right?
Window shakers are designed to work on the circuit that matches the line plug. David is right a general lighting circuit needs to have the right fuse for the wire. It is only dedicated hard wired circuits that get to use the 440 rules that allow bigger O/C devices than 240.4(D) allow.
The installer has no control over what a user will plug in.
My guess is the window shaker is bad.
Greg is 100% correct here, if the AC unit is designed for a 20A circuit then it should have no problems working on the 20A circuit. My guess is that circuit is not dedicated and when the AC starts along with something ELSE probably sharing the circuit it blows the fuse…
As for someone asking are fuses HACR rated…no…that would be delayed fuses but in this case…simply does not matter…putting in 30A on a 20A circuit just to keep it from tripping is wrong…the fuse was doing it’s job.
I know you guys don’t like codes and such, but here’s an interesting tidbit just the same. The International Property Maintenance Code (which would make for interesting reading for any home inspector) actually requires that a fuse panel that shows evidence of overfusing be condemned.
When I go on service calls for a breaker that trips a lot or a fuse that blows a lot (suspected overload), I’ve come to think that all homeowners are liars. I ask them first thing what else goes off when the breaker kicks or the fuse blows. The answer is often “nothing”. When I turn out the fuse or turn off the offending breaker, it seems like half the house goes out. “Nothing” my a55.