In retrospective I would have made things differently concerning the movement of air, I put 2 x 65 m3/min exhausts pulling hot air from aluminium exhausts connected to several machines that connect to 400 mm tubes.
s17+ s17+ T17 T17
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400 mm tube / exhaust pulling 65 m3/min
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65m3/min is (2275 CFM) which should be enough for these 4 miners, but you know you can't exhaust more air than you intake, so even installing 2 or fans might not solve the problem, 400m tube is pretty small especially if the spacing between these miners isn't enough. So until you figure out a way to get rid of that heat, I would suggest you underclock all 4 gears, if it was S9s I would not even bother with 90c, but these 17 series are pretty sensitive to heat and they could die faster than you think if you keep running them this hot.