Your doing what you want and apparently satisfied with it. So why did you start this thread if you didn't want the input from other members here? ... As I said above the hood exhaust is too big and the AC is over-sized. The 13000/15000 BTU AC is capable of cooling up to 900 sqf. Your trailer is only 76 sqf.
The roof top fans are blowing directly down on who ever is working in front of the hood. So if the fans system works as you say, this person is not feeling any cooling from the AC. This air is drawn out by the hood exhaust per your description. If he does feel the AC cool air, then my point has been proven. ... If he doesn't feel the AC cool air, then cooling is from high volume outside cool air flow and the AC is a waste.
In BM kitchens hoods with makeup air are hard to design and maintain. Many hoods don't work as claimed by the installer. But hoods that seem best effective work with approximately 75% makeup air. Higher makeup quantities are greatly effected by close proximity of HVAC vents, doors/windows, or equipment. ... Where Codes now require fresh outside makeup into the HVAC system, higher makeup efficiency of the kitchen hood makeup is not necessary. The kitchen hood can be used as an exhaust for the portion of air being replace by the HVAC makeup system. ... The point of a kitchen makeup air hood system is to save money by reducing the cost of cooling air drawn in from the outside and the size of AC required. A BM commercial kitchen will add a load of 5 ton to 10 tons extra cooling ($600 to $1500 per month) to the building AC load.
So a 15000 BTU AC (900/76 sqf; abt 3 to 5 Xs oversize) will cost you about $6 per day to run. I don't see where you've achieved any savings; but done the same many other trailer/truck vendors; ... just put in an oversize AC blowing on the work area.
Good luck with your trailer & project ...
post edited by edwmax - 2013/10/16 04:27:50