The S-457 was used for the AN/TRR-33 telephone & radio monitoring station. It had an air conditioner installed through the curb side - the AC was usually a 6000 BUT AC with a built in electric heater. Most of the ACs were built by three suppliers, but they were all identical. Hollingsworth built the NSN-4120-01-327-5447 AC. Its covered by TM 9-4120-403-14. You can get this TM at no cost from
Free Military Army Manuals!.
Every one of these ACs is as stuffed with parts as possible. The design is about as complicated as it could be, with bells and whistles that you would never see in a non-military unit. You literally have to tunnel into them to do any repairs.
I bought one of these ACs for my shelter from Coleman's Surplus about a month ago, new-in-the-box. Expensive, but it came in a wood crate, with a barrier-bag, dessicant, and all the rest. The only thing that doesn't come with it is the power cord, and the connector is an oddball - its an Amphenol 5015 series connector with an offset alignment. I checked with surplus dealers, but no one had one - you can order it from Newark Electronics.
My AC needed a freon charge - the charging access ports from Hollingsworth gradually leaked the charge over the 20 years that it had been in a box. I replaced them with a newer style, ran a leak test, and added 2.4 Lbs of R-22. The AC really cools, but the fan is far from quiet. After this summer, though, I'll take a loud fan any day.
The AC units from Coleman come with a zippered flap cover on the outside.
