In publications such as the nLight ECLYPSE™ - Installation Guide at
The recommended values of fuses for 24VAC/DVC supply is shown, but not so for the AC Power to the AC Power supply. Example:
Strictly speaking, this extra protection should not be needed. However, it is a good precaution against faulty wiring, transformers which exceed UL limits, etc. In terms of the AC input wiring, most equipment is already protected by a panel circuit breaker, which is sized to match the branch circuit it protects (e.g. 12 or 14ga wiring, loads, etc.). So, the capacity of this CB would be determined by the electrician. The nECY equipment itself is protected by the internal fuse.