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Bosch Mini Split Installation: Air Handler is pressurized from the factory
I received a BOSCH mini split 18000 BTU brand new in the box from a friend. I studied the installation manual and watched the online DIY videos. Seemed pretty straight forward, the hardest part getting a good seal on the connections, doing a nitrogen leak test, and drawing an adequate vacuum. But as a nuclear engineer all within my capabilities. Heck, I teach how to do swage lock and other copper tube connections at work.
Imagine my surprise when I went to remove the caps on the line set from the air handler to attach the line set from the outdoor unit. The air handler was highly pressurized! As soon as I heard the hissing I immediately re-tightened the cap. What the gas was I don't know. There was no odor (I did not sniff it and went out of my way not to breath it!!). My understanding was that the R410a precharge was in the outdoor unit,
What does this mean? There is no mention of this in the installation manual or any of the online videos. The online videos are for various other brands including popular Japanese brands that look absolutely identical to the Bosch (the internal parts not the exterior). Not one mention of the air handler being pressurized. No results from Google searches.
Mike - Los Alamos National Laboratory
Not a scientist -Just a nuclear garbage man