I used to work on some of the old Bryant, Arkla absorption units. Brooklyn Union Gas was pushing them. They were a piece of work, solution pump problems, belts breaking, and if you were really lucky the leaking generator or hairline crack going into the condensor. That famous bryant bi-metal pilot switch that stuck sometimes. The unsuspecting spider that made a nest in the 3rd burner and delayed the combustion long enough to sound like a grenade landed in your backyard followed by an ammonia stench that could knock you on you a--. That really cleared out the neighbors. Alot of them were installed on rooftops as well. I had every size adapter to fit every bathroom sink so I could connect a garden hose out a window to the roof to fill and clean the brine tank. Ah, and don't forget the evaporators stuck on top of some old GE furnace with a cast iron heat exchanger and a giant blower stuffed in it to get enough air through the 4" round aluminum ducts sized for heating only, and the brine hoses connected by a little piece of clamped rubber hose to the copper or steel brine tubing, when they cracked you were left standing in a sea of green/blue stagnent sludge. They really were pretty inefficient also. (Anyone need a steel 3 valve manifold and charging cylinder?)
I even had one residential customer who had McQuay Hydronic Fan Coils in every room. Two 3 Ton Bryant Chillers and a boiler for heat. He used to bypass the chiller in the winter and the boiler in the summer. It worked well and was designed by him. He was an engineer and a tinkerer.
The latest Robur units are more efficient, but with gas rates what they are, cost a fortune to run. The only places I can see installing one of these is where there is insufficient power available for a conventional unit, or you live in a house with a natural gas well.
Rob