coolhandlew
21-12-2016, 12:26 PM
Hello all,
I work in a data centre, I have been in the trade for a long while but my job now is to oversee contractors work on the cooling plant.
This week we replaced a compressor in a data hall CRAC unit. The unit is a York YC-UPA 932. Twin circuit, DX, downflow, approx 90kW. The compressor is a Panasonic fixed speed scroll C-SCP510H38B.
I didn't witness the actual replacement process but I did witness the folowing;
-Three stage evacuation, each time achieving close to absolute zero with OFN added between vacuums to around atmospheric.
-Refrigerant charged into liquid line R410a to holding pressure.
-Unit started up, further refrigerant charged into suction line (I know what you're going to say but this was done with care).
-All the time system pressures were being monitored, Head pressure was in the region of 24bar, suction pressure was around 8bar, superheat was around 16K. The sightglass was flashing intermittently. Running current was checked on three phases - 17A.
-The compressor sounded fine, no vibration, temperature at the top around 65 degrees C.
-We decided to take a break and let the unit run for half an hour to settle down.
-On our return to the room the compressor was not running, we assumed due to achieving setpoint. We then observed the compressor start.
-It sounded like it had spanners in it! Very noisy, machine gun like.
-We immediately turned it off, I'd estimate that it ran for around 5 seconds, the motor breaker did not trip.
-The temperature on the compressor body was fairly even top and bottom and around 60 degrees C.
-The oil visible in the compressor sightglass was noticeably black, looks like your cars oil after 10000 miles. The level of the oil is good.
-I'm told that prior to the replacement the system pipework was purged (blasted through) with OFN.
Obviously we checked three phases present, and rotation.
It had ran fairly sweetly for an hour.
Is it possible a bearing could break up in an hour and allow the scroll to clang about but not trip the MCB?
I wondered whether the contactor may have only closed on two phases intermittently, I would have expected more heat though, and probably clean oil.
The filter drier was changed also at the same time.
This was a brand new compressor, failed after one hour.
Any ideas/suggestions greatly appreciated.
I work in a data centre, I have been in the trade for a long while but my job now is to oversee contractors work on the cooling plant.
This week we replaced a compressor in a data hall CRAC unit. The unit is a York YC-UPA 932. Twin circuit, DX, downflow, approx 90kW. The compressor is a Panasonic fixed speed scroll C-SCP510H38B.
I didn't witness the actual replacement process but I did witness the folowing;
-Three stage evacuation, each time achieving close to absolute zero with OFN added between vacuums to around atmospheric.
-Refrigerant charged into liquid line R410a to holding pressure.
-Unit started up, further refrigerant charged into suction line (I know what you're going to say but this was done with care).
-All the time system pressures were being monitored, Head pressure was in the region of 24bar, suction pressure was around 8bar, superheat was around 16K. The sightglass was flashing intermittently. Running current was checked on three phases - 17A.
-The compressor sounded fine, no vibration, temperature at the top around 65 degrees C.
-We decided to take a break and let the unit run for half an hour to settle down.
-On our return to the room the compressor was not running, we assumed due to achieving setpoint. We then observed the compressor start.
-It sounded like it had spanners in it! Very noisy, machine gun like.
-We immediately turned it off, I'd estimate that it ran for around 5 seconds, the motor breaker did not trip.
-The temperature on the compressor body was fairly even top and bottom and around 60 degrees C.
-The oil visible in the compressor sightglass was noticeably black, looks like your cars oil after 10000 miles. The level of the oil is good.
-I'm told that prior to the replacement the system pipework was purged (blasted through) with OFN.
Obviously we checked three phases present, and rotation.
It had ran fairly sweetly for an hour.
Is it possible a bearing could break up in an hour and allow the scroll to clang about but not trip the MCB?
I wondered whether the contactor may have only closed on two phases intermittently, I would have expected more heat though, and probably clean oil.
The filter drier was changed also at the same time.
This was a brand new compressor, failed after one hour.
Any ideas/suggestions greatly appreciated.