I have an existing dedicated circuit providing power to my residential well. It is a 240v circuit and has a 30 amps double breaker. I would like to install a manual transfer switch, "Emergen" (Conneticut Electric) model 10-7501 to the circuit, however they warn against connecting to any circuit having more than 20 amps. I assume this is rating limit of the transfer switch circuits. The pump motor of my well uses only about 10 amps to run... so my question is... can I replace the 30 amp breaker in the load pannel with a 20 amp breaker to comply with the requirements of the transfer switch, and still provide sufficient amperage to operate the well? I believe the wiring from the pannel to the well is 10 gauge if that is relevant.

Well... you can try that. The starting load of the well pump will determine if it is acceptable. How do you know what the pump requires to run? 10 gauge wiring requires no more than a 30 amp breaker. Your pump may need less to run, but the distance between the breaker panel and the pump also is a factor in the wire size and the breaker capacity. If it was my installation, I would look for a transfer switch which could handle a 30 amp load... just my opinion.