I need to install a 30 amp breaker for an electric washer dryer that requires 230 volts in a 40 amp modern fuse panel box for a apartment. The box is fused with a 40 amp main breaker within an apartment house in the NY area serviced by Con Edison. One existing breaker is a dedicated 20 amp circuit for the 220 Air conditioner. I am hoping that I can mount a dial switch on the wall beside the panel (with a licensed electrician) that will allow only one unit to operate at a time with the correct amperage breaker for each unit to make sure safe conditions are maintained. I do not want to use any kind of knife switch or a generator transfer switch if at all possible. Thank you for your help.
I am a bit confused by the question - I think you're saying there's a 40 amp panel with a 20 amp two pole breaker for an air conditioner you want to add a 30 amp breaker for a washer dryer unit, and you want to make sure the washer breaker and the air conditioner breaker don't go on at the same time. (Also, are you thinking break before make, and have it reversed in the question's title?)
Would it work to use a 30 amp DPDT switch on a 30 amp breaker, one throw going to the washer dryer, the other going to a disconnect with a 20 amp breaker feeding the existing air conditioner? For example this one
looks at a glance like it would be adequate.
The AC and it's existing wiring probably has to be on a 20 amp breaker, so you couldn't just connect it to the switch. I think you could find a 20 amp disconnect to go between the AC throw of the switch and the existing wiring.
Is there another panel for the apartment? With all this on 40 amp main I'd see a lot of trips.