[rsatz28]

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For a 60x100 you'll need 12 tons. thats 500 sq.ft. a ton. if your doing ground source in the house, while the contractors there drilling the wells go ahead and have him drill wells for the garage. one well for each ton. when installing the ductwork, if you supply up high, the return should be low, and visversa. be carefull if you bring in oa to the system, so as you don't bring in to much. to much will cause humidity problems if the equipment is not sized to over come it.

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While the initial cost may be a bit more, you may want to install two smaller units (that add up to 12 tons) so that they can be staged for better humidity and temerature control. I do not think you can get a 12 ton single phase unit, but would have to go with a 3-phase unit.


An oversized unit will short cycle the unit (esp the compressor in AC mode) to death. Aslo, the "noise" factor may be an issue.

Electrical costs may be lower running lower HP blowers, compressors and condesner fan motors.

Keep in mind that you will only need max heating and cooling a samll portion of the year.