Hi Michael,
We have not tested 19.5v, 240watts 12.3a AC Adapter with this system. We have only tested 180 W AC Adapter with Discrete GPU and 150 W AC Adapter with Integrated GPU. You may use it and it might work.
If you are referring to the following part (as shown in the image), then the part # is 5PP3X (Touch) or 776H4 (Non-Touch).
Hope this information helps.