Peter, the two bolded lines are confusing. Did the electrician use 20 amp breakers for your 30 amp circuits? If so, what makes the circuit '30 amps'?
Can’t answer that Ian. The breakers are rated for 20 A but it’s a 30 amp circuit based on the wiring used. I think the breaker is just rated to trip at that level but that the line can carry more power.
certainly others will have a better answer for you.