Challenger 350 Captain reported a pack duct leak after departure and a return to the origin airport.

Narrative

After a normal coast out we experienced a PACK LEAK RED Crew Alert System (CAS) with Aural Warnings. As a crew we went to the checklist which commanded a few tasks. The check list said go to Trim Air only which we did. This flooded the cockpit and cabin with raw bleed air in excess of 55c. There was no change after 90 seconds . Using power we were able to mitigate the load rush of air and extreme heat. We started to descend to the commanded altitude of 9000 feet. I left my station for a few moments to tell the passengers we had an issue and needed to return to ZZZ. ATC gave us a decent to 15000 feet and headings with a subsequent fixes for a reroute. We were approximately 200 miles off shore. With throttles to idle the temps came down and the PACK LEAK RED CAS extinguished. This was the second time I left my seat to tell the passengers that the checklist commands the aircraft to be depressurized. This would mitigate the raw air rushing into the cabin and make the flight less unpleasant. We reviewed what it would feel like to depressurize the plane. I reviewed some personal ways to clear the ears if it became uncomfortable. When it came time to depressurizing the plane we turned the Air Source to off which allowed the plane to gradually meet our current altitude. When the depressurization was not going to be as extreme we selected Emergency Depressed and then went to RAM Air on; adhering to the limitations. We made an uneventful landing where the passengers were gracious and curious about what had happened. We surmised that if this was going to happen; it happened at a perfect time . The alternative could have been mask usage or a swim in the pacific.Suggestions: There are many problems with the Challenger checklist that should be addressed. If we had reached our ETP and this had happened we would have had to NOT follow the checklist in order to have gas and make a coast. The checklist needs to reflect a 15;000 foot alternative to make a coast at an ETP. Since long range cruise numbers are not reflected at 9000 feet in any chart I have seen we would have been test pilots and possibility Raft boat Captains.The other issue was the Duct overheat with the usage of TRIM AIR. There is no time in the checklist that trim air can be used. Obviously in a Drift Down scenario where we were descending at 2000 feet per min for 15 mins the Trim air is overheating the ductwork. The manufacturer should have a idea of time that unconditioned air can run within the duct work before the messages appear or catastrophic damage is done to the duct work.