I have 2 questions: since there are 3 terminals on the circuit breaker (2 for hot, one for neutral) how do I wire the breaker with only 2 wires? Second question is I ran 14 gauge wire as per the manufacturers specs. But I understand that 14 is insufficient for a 20 amp breaker. But that's also what the dealer recommends. I'm confused.

Why a gfi for a heat pump?

Can you provide a make and model number of the unit?