The calculator is useless. Doesn't ask about ducting/ventilation (lights), insulation, external temps, ceiling height, subroom housing ballasts having/lacking it's own insulation/ventilation and proximity, and a "bagillion" other variables.
It all boils down to this, a 4 ton will not properly cool a 10 light room (if 1k a piece) without additional measures in place (e.g.; ducting and complementary cfpm blowers), or extreme external influence (e.g.; it's snowing outside and the room is being cooled due to poor insulation, or internal/external air exchange). It just won't.
The redoubt of 115*F could be inaccurate. The thermostat may have a maximum temp display (i.e.; 115*F). IMHO, it was much hotter than 115.
Regarding 410A VS R22 efficiency/cooling capability, we'll have to agree to disagree. 410a has significant advantages over R22. "Night and day" these two. "Google it" (RIU inside joke now). That being said, newer setup, more than likely 410a, unless HVAC guy is moving discounted R22 units for bigger profit as well as charging an arm and a leg for R22 (liquid gold). She did say 9 G's (ouch).
No, but you don't want your AC constantly fighting your lights either. Have you ever run a ductless 10k+ room? It's tough to "beat the heat".
I'm just trying to help out, hate to see someone lose their crop to equipment failure. Also, not trying to be "negative" (
@Snoopy36 ), but Unicorns don't always shit Rainbows.