Ok heres one that will stump you. Well it stummped me and my HVAC buddies anyways.

The lobby unit in our building has been running 24/7 for 3 years with no problems. Then one day out of no where we found the main breaker for the unit tripped. After a quick investigation we reset the breaker and the compressors sounded horrible. we assumed a mechanical failure, but threw guages on it anyways and found the pressures to be equal while the compressor was "running".

So heres where it gets interesting. The fan is rotating properly, however my boss decided to switch 2 of the 3 legs on the compressor to change its direction and what do you know, the compressor ran perfect!

Hopefully i gave you guys enough info. So what do you think, were stumped?