I think destilled water is only relevant for watercooling, because the effort to keep it dielectic is too high, right?

Regarding the PSU the 92% Efficiency of Alphaminer PSU tells me that heat development of PSU (8%) is much less then heat development of Hashboards (92%). Is watercooling meaningful for PSU, due to "centralized" heat sources (like asics at the hashboards) or is it unsuitable?

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Regarding coolant of immersion cooling i guess safety effort is a tradoff for other requierements. Obviously non flammable coolant is desirable, but i am not sure if one should take it absolute. For example Propan and Butan are coolants for heat pumps, low climate impact, low price, dielectric and good thermal characteristics, but flamable. I guess no one ever tried that as a coolant for mining hardware (i will neither), but i would not rule out that, because with highter safety effort the risk seems to be manageable.