The air comes in through a filter vent on the top back. I am thinking the efficiency not being very good. This unit is very directional, meaning that like the propane heater, it is comfortable when in front of the unit, even at 25' away, but it seems to do little more than knock a few degrees off the overall shop temperature. I do notice a big difference in the drop of humidity in the shop which is greatly appreciated.
I will most likely use this through this summer and be able to report on the days that hit 110 in the shade, in the mean I will be looking into a split system type as this sounds like another option that will work in my situation (not wanting to cut large holes in the walls). Preliminary search at Home Depot shows a 18,000 btu unit for $1,200.00 but with very poor reviews.
It is 9:30 right now and the wall temp shows 81, the unit reports 77. Where I am setting it feels like 80, but if I direct the unit in my direction it feels like 77. Yes I placed an oscillating fan on top, it doesn't have enough cold output to cool the whole shop, and the unit hasn't cycled once sense I placed it in service.
I may pick up some tarps and split the shop like I did my old one so I am only cooling a 12 X 18 area instead of the full 24 X 18. This seemed to work well when I was heating the 12 X 24 last winter.
At least I can easily move this unit from one side of the shop to the other depending on what I am working on. The Tractors dont need A/C unless I am working on them.