I recently added a garage/ storage area to our house and I don't want to plum it into our existing HVAC system. I was looking at the PTAC systems that are available. We used them overseas and were pretty impressed with the ease of setup compared to standard HVAC systems with ductwork.

Questoin is regarding the size I need.
They list them in BTU/HR and I would like to know what size I need.

The garage dimensions are 480 SF with 10 foot ceilings. The walls and ceiling are insulated with r19 and covered with sheetrock.
The foor is concrete. The temerature extemes are at a minumum. Summer temps are in the high 80's and winter low's average in the high 20's.

If there are any drawbacks to the PTAC systems please let me know.

Thanks
Dolomite

They work  fine, but you have to cut a  pretty large  hole in your wall to install them.  A ductless split system might be a better choice.  

They look like this.  split system

They are easy to install.  They are quiet.  

I'd say you would need around a 12,000 BTU unit.

That would be ideal for a garage, 1.5 should do it 2 ton might be over kill but would probably be ok.

What part of TN are you in?

East of Knoxville.

Dolomite

Thanks, those are the ones I was meaning.

Dolomite

IM semt

stay away from anything that says "FRIEDRICH" on it.   Complete junk!!!