Have HVAC Questions? Ask an HVAC Expert for Answers
Hi I'm Brian and I'm here to help!
I believe if you look closely at the wiring diagram that the mechanical high pressure switches (not pressure transducers) are in series with the motor overload circuit. I would check for problems with the condenser fans or condenser coils. I'll see if I can find my manual for these models and try to confirm my suspicion but I've experienced this same issue on a few York chillers and it wasn't the motor or motor control at all, it was the high pressure cut out peanut relays.
Click Here for a copy of the York IOM manual for the chiller in question. In detail A on page 76 you can see what I was talking about with the high pressure switch being in series with the motor overload circuit M1-M2. Check the condenser fan starters or contactors, check the condenser fans themselves and check the condenser coils for fouling. I believe you will find your problem there.
Let me know if you have further questions on this subject. Otherwise, please remember to rate before leaving (3 stars or higher please!). Bonuses are always appreciated! Thanks for allowing me to help and thanks for using Just Answer!
That sounds pretty odd indeed. Can you give me the FULL model number of the unit please? Do you know if the unit is Xline start or Wye-Delta start? If it's Wye-Delta, are the starters transitioning properly? I would also check the load/unload solenoids. You can dry run them with jumpers. I've not got a whole lot of experience on the smaller York semi-hermetic screw compressors but at 30 seconds after start, they should just be starting to load so that is rather odd unless the unload solenoid isn't working or the slide valve isn't operating. Are you saying both compressors are doing the exact same thing? That in itself doesn't lend itself to a solenoid or slide valve issue. If both compressors are behaving the same way, I would look for some kind of electric commonality. I would test run everything that can be with jumpers at the control output relays (with the exception of the compressors) to see that everything operates properly from the control panel. Have you double checked voltage, amp draw and system pressures to make sure they jibe with the control panel readings? If you can get me the model number info and answer as many questions I've asked above, I may be able to get a clearer picture of things. As I'm sure you can imagine, it's tough to troubleshoot a chiller this complicated remotely but I'll do my best!