Please tell me what gauge wiring {for example 12/2 or 12/3} and breaker amperage {for example 30 amp 2 pole} I need for a 220 volt wall heater.:confused:

12-2 is 2 conductor w/ground. Good for 20 amps. If it requires 30 amps, you need 10-2 w/ground, if neutral is required then you will need 3 conductors plus ground.