Yes, when you plug the air conditioner in to an ordinary house receptacle this is the configuration that exists. Just make sure that additional loads on that same circuit are not any more that 7.5 amps or the circuit breaker will trip. For air conditioners it is best to have a dedicated circuit right back to the distribution panel. This means that there can be only one appliance, the air conditioner, on that specific circuit.
You need a 60 amp breaker.
If the 12,000 BTU A/C only requires 20 amps to run then yes you can use the same 12 gauge wire but you cannot change it to a 15 amp breaker. You will need to install a 20 amp double pole breaker. If it requires more than 20 amps you will have to replace the wiring and breaker.
Minimum size is 10 gauge with a 30 amp breaker. To be safe I would install an 8 gauge with a 40 amp breaker.
15 amps
Yes, as long as the fuse or circuit breaker is rated for the smallest wire in the circuit, which in this case appears to be the 14 guage. Suppose the 14 guage is rated for 15 amps and the the 12 guage is rated for 20, and there is a 20-amp breaker on the circuit. Now suppose you have a short that draws 18 amps. The 14 guage wire will burn and catch fire, yet the breaker will not trip. That could be dangerous.
You need a 60 amp breaker.
Assuming 120 VAC in a residence maximum watts = 15 x 120 = 1800 Watts. For a continuous load you can support 1440 watts which is 80& of maximum. You need 14 AWG gauge wire.
If the 12,000 BTU A/C only requires 20 amps to run then yes you can use the same 12 gauge wire but you cannot change it to a 15 amp breaker. You will need to install a 20 amp double pole breaker. If it requires more than 20 amps you will have to replace the wiring and breaker.
14 gauge will handle it with a 15 amp breaker. If you use 12 gauge use a 20 amp breaker.
Minimum size is 10 gauge with a 30 amp breaker. To be safe I would install an 8 gauge with a 40 amp breaker.
No. A 20 amp breaker needs 12 gauge wire.
30 amp breaker with #10 gauge copper wire
AWG 12.
10 guage.
15 amps
You listed no gauge wire. This is the required breakers.14 gauge - 15 amp12 gauge - 20 amp10 gauge - 30 amp8 gauge - 40 amp
Normally it is a 20 amp using AWG 12/2 gauge wire. But it really depends on what size wire is on that circuit. If it is white AWG 14 gauge then use a 15 amp breaker. If it is yellow AWG 12 gauge then use a 20 amp breaker.