I could be wrong, but regular "name" manufacturers like Trane, Carrier, Bryant, York, Rheem, Ruud etc.... all start at 18,000 btu's (1.5 tons) for condensing units. For a 12,000 btu condensing unit, you will very likely need a portable unit, window unit, through the wall unit (like a hotel has) or a ductless mini split system.
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