As with the other subjects of interest, such as boilers, chillers etc, I thought I'd start a thread to answer questions regarding the old pneumatic 3 pipe systems that are rarely ever seen.
I have attached a picture below. What exactly am I looking at? I know it’s a Unit ventilator of some kind, is it three pipe etc? What are the two small doors near the grill used for (one is on the right, one on the left)? Are these systems strictly pneumatic, and seen only in older installations? I don’t see these units in new construction, when did this style unit go out of favor with architects. Are any still made today?
NOTE: I’m not talking about the “hotel units’, which look similar but function on their own. I believe the system I’m referring to requires a boiler/chiller to operate as the door on the left typically reveals pipes going into the wall.
I apologize if this has already been discussed.