I am building a shop and did not plan for a heat/air unit. I thought just an overhead heat. But now I have a heat /air unit out of a house for free. I have a drain in the middle of the floor, but did not plan fot drain for A/C, The only option I can think of is drilling down, about 5" to the exsisting drain pipe. Any other suggestions??

Better option is a condensation pump.
Usually just a small plastic box with a small pump. Condensation drains into reservoir, pump comes on when reservoir is full and pumps water up and out.

Harold has the best answer for you. A condensate pump is the only way to go for this. No need to break up concrete. You can take the discharge of the pump either to an accessible drain or vent line, or simply pump it outside.

If the unit is grade level or above, just put a 1/2 " pvc pipe from the A coil tray and let it gravity feed outside, mine does.

Ma, that works great for ac, but if the furnace is a 90+ efficient unit, the line will freeze in the winter if it gets really cold, due to the slow flow. It may work for you and may even work for grbaker, but in my area, been there, tried it, and they froze up the first cold spell. A condensate pump pushes a larger volume of water so it doesn't have to time to freeze. However, when running a condensate pump, I always make sure to pitch the disharge downwards towards the outside so there is no standing water in or outside of the exterior wall.

ma, that works great for ac, but if the furnace is a 90+ efficient unit, the line will freeze in the winter if it gets really cold, due to the slow flow. It may work for you and may even work for grbaker, but in my area, been there, tried it, and they froze up the first cold spell. A condensate pump pushes a larger volume of water so it doesnt have to time to freeze. However, when running a condensate pump, I always make sure to pitch the disharge downwards towards the outside so there is no standing water in or outside of the exterior wall.

Yes, my 92% is run through a condensate pump but my 80% is gravity. In Georgia, we don't usually have that issue although in 1978 or so, it hit -4 in Atlanta. Plumber loved it!