Take a look at the attached guideline, and note that the rear discharge method is what your talking about. Bringing the air in from other than ducting within the hood should be no problem, its the location of the outlets thats important. But be very careful about brining it in from a low location, especially anywhere near the truck exhaust, side up high will be better. Putting the outlets low behind the equipment is a very good place. The important thing is that the location of these vents is such that the makeup air is able to pass thru the exhaust hood leaving as much as possible the room air undisturbed. If you look at the pictures in the attachments they show the spillage plumes of different configurations. One of the best would be from the rear of the equipment. Engineer your hood and makeup air, don't just pick parts and install them. The avantage of a closed circuit system is that the exhaust and mua are already balanced, but the same can be done with seperate components.
Calculate the exhaust cfm and mua cfm required and balance them. You can then adjust this by using a damper on your mua intake. One way to play with spillage is to use joss sticks to see where the air is going. Venting your a/c such that it blows away from the exhaust hood will help from disturbing the air flow between the mua intake and the exhaust. Keeping your service window small and easy to open and close. The reason a lot of kitchens are hot is they do not properly engineer the makeup air, just buy stuff and put it in.
The worst most useless is a short circuit hood, as described in the attachments, yet they are sold by these so called professional companies every day!http://www.fishnick.com/v...ign_Guide_2_031504.pdf