External fuses and circuit breakers,like those in a house's panelboard, have never been intended to generally prevent equipment from failing. Of course there will be some situations where the branch circuit device also acts as the motor protection, but then different sizing rules come into play.
If branch circuit protective devices, were intended to keep compressors from failing, we would not have verbiage in the code like NEC 2005 440.2 which allows for "greater than the marked rated-load current'.
The maximum protective device value from an equipment manufacturer may not have been sized to prevent a failure. The equipment often contains a compressor and a fan or two, so the branch device must inherently be larger than one chosen just for any of the individual components.
Regardless, if the manufacturer's instructions were not followed, pursue a warranty claim may be difficult.
I would not expect an electrician to investigate the correctness of protective device sizing, if the contract was 'replacement of existing'. However, I would expect the owner to be notified of common code compliance issues such as 110.3, 110.9, 110.14, and 240.4(D) which may become apparent during any replacement.
