Isolating Refrigerant in Evaporator or Condenser RTAA

Issue:

Isolating Refrigerant in Evaporator or Condenser

Resolution:

The nameplate refrigerant charge can be isolated in either the condenser or the evaporator on all RTAA packaged chillers.   Please refer to RTAA-SB-10 for more information.

DO NOT ALLOW THE SUCTION PRESSURE TO DROP BELOW 20 PSIG OR CATASTROPHIC COMPRESSOR FAILURE COULD OCCUR.

• When isolating charge in the evaporator, if possible, run the chiller for a few minutes in order to lower the evaporator temperature.  Just before shutting the circuit down, unplug the circuit's expansion valve.  Once the circuit stops, shut the suction service valve and allow the refrigerant to migrate from the condenser to the evap.  Watch the sightglass, and, after the refrigerant stops flowing, close the liquid line angle valve.  You can then recover the remaining refrigerant.  Don't forget to plug the EXV back in.
• If you cannot run the circuit, you may still be able to move the refrigerant by running the other circuit.  You can then shut the chiller down and perform an EXV test on the problem circuit (as long as the EXV is not the problem to begin with).  The EXV will begin to click almost immediately.  It will then be silent for about 15 seconds and will begin clicking again.  When this second set of clicks occurs, unplug the EXV (it will then be in the open position).  By its nature, refrigerant will want to occupy the coldest space that it can, so if you close the suction service valve and allow the liquid to move to the evap, you can watch the sightglass and when it clears, close the liquid line angle valve.  You can then recover the remaining refrigerant.  Don't forget to plug the EXV back in.
• When isolating the charge in the condenser, you can perform a Service Pumpdown.  ALWAYS CONNECT A GAUGE TO THE SUCTION LINE prior to pumping the circuit down.  With the circuit off, close the liquid line angle valve and perform a pumpdown.  Monitor the suction gauge, and prepare to shut the circuit off when the compressor is no lower than 20 psig.

DO NOT ALLOW THE SUCTION PRESSURE TO DROP BELOW 20 PSIG OR CATASTROPHIC COMPRESSOR FAILURE COULD OCCUR.

• Be prepared to terminate the pumpdown process by throwing the disconnect, pulling a wire from the high pressure cutout, or some other mechanical means.  DO NOT RELY ON THE CONTROLS TO TERMINATE THE PUMPDOWN PROCESS.
• The Service Pumpdown feature for RTAA is based on a 1 minute timer.  Once engaged, the compressor will run and disregard the "Low Evaporator Refrigerant Temperature" diagnostic.  On smaller units, one minute is more than enough time to reach 20 psig, therefore, you must be prepared to terminate the pumpdown prior to one minute.
• Once the process is complete, close the suction or discharge service valve.
• To isolate the compressor alone, close the discharge and suction service valves along with the oil line angle valve.  Connect the recovery equipment between the compressor and the "low side". 

USE EXTREME CAUTION WHEN WORKING WITH LIVE POWER. 

• Using jumpers, energize the load and unload solenoids to ensure that the piston cavity (or cavities) are evacuated.  Also, if working on an RTAA 130-400, use jumpers and energize the master oil solenoid to remove pressure between the solenoid and the oil line angle valve.

Notes:

Changes:

Other Question/Problem/Cause Statements:

• Isolating Refrigerant in Evaporator or Condenser

Facts:

• RTAA 130-400 Ton (Pueblo)
• RTAA 70-125 Ton (Pueblo)