I could use a little help from all you commercial guys out there that work on a lot of Trane package units. I was called today to look at several units ( 2-15 tons, 1-12.5 ton & 1-7.5 ton). I have done some work on their residential lines but not on the commercial stuff.

Here's what i have. 7.5 ton package unit, all electric, 230vac 3 phase, 2 circuits, one 4 ton & the other 3.5 ton. Unit was not running except for the blower. Pulled the door off, installed gauges on both compressors, checked voltage (had it) checked transformer (had 24vac out), t-stat set to cool. Working with a lot of York's, i know if they have problems, the board shuts the compressors off & they stay off until you reset the breaker. That's what i did here. Turned the breaker off.... then on. Waited about 5 minutes, compressor #1 came on, along with cond.fan. A few seconds later compressor #2 came on. After about 10 seconds, head pressure pegged my gauge, and the unit shut off. No frosting in that short of time that i could see. Back to where i started, but i know i have a restriction somewhere.

This is what I'm unfamiliar with: I couldn't find a TXV or a flow-rater anywhere. Looks like both liquid lines come straight out of the condenser, thru 2 extruded dryers (gonna pull them off tomorrow) and straight into the evap coils header pipe. Did not see any cap tubes, nothing. Am i missing something? Are they using the overall length of the liquid line as a cap tube?

Any help would be appreciated.