My boss sent me to relocate 2 a/c feeds, rooftop units. The existing units have 90 amp breakers on #4 thhn. The new units have the need for 60 amp, so since the brekers for the original units are hard to get, and expensive, a 3 phase disconnect (100 amp) with 60 amp fuses, (mounted on the unit) will protect the unit. One of the mechanics at the shop thought you could get away with a 60 amp fused disconnect, but I say that you have to go by the rating of the highest amperage. I only have the handbook at home, but I don't see a reference to this. Also, if one of the fuses lets go, will the unit burn up? (becasue of running on single phase?) Thanks for any help on this.
