[So Cal Rocket]

connected to an 80Cubic Foot gas bottle charged to ~2300PSI

It should work, so long as the fire gets to the sprinkler head before it gets to this bomb.

[Old Professer]

It is not a bomb; the bottle will be charged with air.

Fire sprinkler heads normally cover 100 square-foot areas and any fire in an enclosed area will cause a curtain of heat to rise up the walls along the ceiling and trigger the head before the temperature in the room rises 15 degrees overall.

Even if one took a cutting-torch directly to the tank while in the room the sprinkler would go off and drown the silly-ass trying such a stunt long before he could heat the tank to raise the pressure to a critical point.

An 80 degreeF temperature change on a car tire will only result in a 5PSI change.

If what you suggest would be a concern, a simple 16gauge metal cabinet around the assembly would shield quite effectively.

[Recluse]

I think the converted hot water tank will rupture quite immediately.