Can I use the same siphon that I use to fill bottles to move water from my hot water kettle into my fermenting cooler?
I would not use it for anything very hot. Max would be strike water at about 170. I personally would not even go that high. Why not cool first then transfer to the fermentation vessel? What exactly are you moving to the fermentation vessel? Wort should be cooled first.
If it is a PET bottle, they are only rated for 140 degrees anyway. Much more than that will deform the bottle, ask me how I know......