I don't know the exact details of your install but, a double pole 20 amp breaker is more than sufficient for that blower, #10 wire is more than sufficient for the 20 amp breaker and #8 bond is standard bonding.
#12 wire is good for 20 amps
#14 wire is good for 15 amps (I never use #14 wire, even on a 15 amp circuit, I use #12, so that I have the option to use a 20 amp breaker if I ever need to upgrade the circuit)
Now what I don't know is the internal wiring for the blower. The manual for installation should have a recommended breaker size. You should always use the breaker sized for the weakest part of the system. If the internal wiring in the blower is #14, you shouldn't use a breaker bigger than 15 amps.
The breaker is to protect wiring. Electricity flowing causes some heat in the wires, if you use a breaker with too high of an amperage rating, in an abnormal condition, such as a partial short circuit, the wires can overheat and start a fire. It's always best to use a breaker matched to the weakest part of the circuit, and wires capable of handling rated amperage or higher amperage than the breaker feeding the circuit.
