Generally, we advise connecting the hot (or live) wire to the N/O (normally open) terminal, then connect the COM terminal to the solenoid. That way, when the relay is open, the hot wire is not connected to any other terminal. If you were using K2 on the PMDX-126 and wired the hot wire to the COM terminal, it would be connected to the N/C terminal whenever the relay was de-energized.
The N (neutral) wire should go directly from the A/C outlet to the air solenoid. If the solenoid has a connection for the ground/earth wire, then run that also directly from the A/C outlet to the solenoid.
Bob