I recently had a 3 ton Trane XL16i with a 4TEE3F40A VS air handler installed. The Outside unit came pre-charged from the "shop".
The Salesperson was Extremely thorough with his measurements/calculations etc. (they pre-fabricated the ductwork at the "shop" based on his measurements... which fit like a glove by the way...)
The installers said Because of the exact PRE-measurements of the NEW linesets, all they had to do after they brazed and evacuated the system with a vacuum pump for 45 minutes, was to open the "charging valves" and presto! chango! the system is PROPERLY CHARGED!!!
Is this a "normal" procedure??? Or a cheapo shortcut???
P.S. they DID NOT add or remove any Puron following installation... BTW, I am Very Pleased with the operation of this system, just thought it was strange the way the "charge" was administered...