Fusebox Bad?

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?



A slow blow type fuse at 20amps should work.

Do they make HACR type fuses?

Over sized breakers are ok on compressor circuits so maybe this is allowed?

Wait on the electricians to respond I guess.

In my book, this 30 amp fuse is not allowed. I call out all 30 amp fuses on #12 AWG.

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.

Give it a time out…:cool:

When in doubt…refer it out.

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.

Got agree with Paul about this. If you found a 20 Amp breaker on 15 AWG wire because the microwave and the toaster keep blowing the circuit, you would call it out. Same diagnosis.

“Normal household circuit” are standard and any deviations from the standard are wrong. :smiley:


All i know is I love that word…“condemned”…always have…I wanna be a slum lord when I grow up.

I guess that’s why you make the big bucks. You are probably right on that.

“The A/C goes out and the microwave screws up my popcorn” :wink:

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.