Just serviced (3)trane 20 ton roof top packaged units. Manufactured in 2001. Each unit has (2) 3D Scroll compressors. These are not tandom compressors.
2 Units have bad second stage Compressors. The contactors arnt burnt and look clean. Phasing is correct. Coils are clean, Air flow (cfm) are correct etc. Both compressors are burnouts. Each unit has phase protectors which are wired correctly and voltage and phases are balanced. Circuits are fully charged. (weighed removed refrigerant).
Upon looking at the third unit, the first stage compressor is cutting in and out. Looking at the liquid line filter drier frosted up its not hard to figure out why.
Every compressor and drier still have to red paint crap Trane puts on the braized connections, so its obvious this is all original.
This is 3 year old equipment!! The owner wasn't very happy to find so many problems on basicly new units.
Today he had me go to another building he owns with 2 trane units and 1 Carrier. Trane units are manufactured in 99.
Almost same story. 1 unit has no charge in it. Charged with nitrogen. Condenser has huge split in the coils. The second unit has a dead short in the second stage compressor.
I dont think the owner will be buying anymore trane units.
Im not going to complain. Trane is gona make me rich with all this work!!! Heck i even found 3 cracked condenser fan blades out of 5 units.
The Carrier is a 91. Its still cranking. (scratching head)