The PowerChute initialization file is a complicated file that should be set up by the PowerChute install script /usr/lib/powerchute/Config.sh. However, if you just change the serial port that the UPS is connected to, you could edit the one section in the init file that describes which port to use.
/usr/lib/powerchute/powerchute.ini:
Set the serial port to something else (choices are ttyS0 and ttyS1).
[ Ups ] SignallingType = smart PortName = /dev/ttyS0 AutoUpsRebootEnabled = Yes AllowedPortNames = /dev/ttyS0,/dev/ttyS1 CableType = Normal