So lost - electrical requirements please help
In order to provide you with accurate information we need to know specific equipment requirements.
First I'll address the outdoor unit (I am assuming that the air handler with heat-strip is a separate piece of equipment).
All Heat-Pumps/AC Condensing Units have two relevant circuit ratings. Rarely are they properly adhered to.
The first rating is "MAX FUSE or HACR CIRCUIT BREAKER" This is required by law for one purpose only: fire prevention.
The second rating is "Minimum Circuit Ampacity" This is the relevant guide for sizing the circuit. The correct size circuit is equal to or slightly greater than this figure.
I'll provide my home as an example and indicate how the builder (HVAC subcontractor/Electrical subcontractor) violated the code.
My outdoor unit:
MAX FUSE or HACR CIRCUIT BREAKER: 35A
Minimum Circuit Ampacity: 22.7A
The builder installed a 30A circuit (Number 10 wire) with a 35A circuit breaker. It is a code violation for the circuit breaker to be greater that the circuit ampacity which is 30A for the number 10 wire. In reality, no fire will result from a fault in this installation because the 35A breaker meets the unit requirements and the wire will handle the 16% over-rating.
A valid no-brainer installation for my unit would be a 30A circuit (Number 10 wire) with a 30A circuit breaker. However, this would not provide adequate overload protection for the compressor.
The correct installation for my example is a 30A circuit (Number 10 wire) with a 25A circuit breaker. The circuit breaker should always be the smallest size that is equal to or greater than the "Minimum Circuit Ampacity" This is why "in-between" sized circuit breakers are made such as 25A, 35A, etc. - to provide electric motors with optimum overload protection. The unit or thermostat should have a re-cycle timer to guard against nuisance tripping on re-starts.
Being that your home is 820 sq. ft., I am hoping that you have a 2-ton heat-pump. Any larger would result in drafty short cycling. When sizing an air conditioner, less = more (comfort). A 2-ton heat-pump will typically have a "Minimum Circuit Ampacity" of less than 20A. So report on what you have.
Now onto the indoor equipment. The typical indoor air handler with heat-strip requires one circuit. 30A if equipped with a 5KW heat-strip, 60A if equipped with a 10KW heat-strip. Occasionally, the heat-strip is a separate piece of equipment requiring its own circuit. Note: if there is no heat-strip in the air handler, and thus it has its own circuit, the circuit should be 15A maximun for the air handler only. As it is, the blower motors in these units never have adequate protection.
Your circuits seem way too large for applying HVAC to 820 sq. ft. A 2-ton air handler will barely provide enough air flow for 10KW heat.
Let us know exactly what equipment you have and a clue as to why this new installation needs to be rewired. Obviously we don't know what the obstacles are your installation, that said, the quote that you received seems about double what it should be.