1.5 Ton Unit For This Room Size Is OK..........There Are Many Factors Which Matters
Room Temp , Humidity...Outdoor Temp......And Then Comes How Unit Is Charged And is Operating......!
If Its Low On Refrigerent Or Also HIGH...System Won't Work ......! High Head Pressure Cause issues In Cooling....
My 15 x 15 x 14 Room With 1 Ton Unit Drops Down Temp 3-4 Degrees In Less Than 15-16min......
Height Of Room Also matters......And If Roof/Wall Of Room Are In Direct Contact With Sunlight......It Will Decrease Performance Of A/C Too