have a large walk in storage Freezer designed for -15F. We currently are at -8F. System has (2) 30HP Hussman SLD 0301 L4M air cooled condensing units with clean coils with matching remote electric defrost evaporators. One of the system's had R404A gas added every few months or so due the flashing sightglass. We recently leaked checked the condensing unit found no leaks, then added dye to system checked entire condensing unit had piping down to the evaporator and still no leaks. Then found 1/3 ice covered evaporator, found defrost needed repair fix it and cleared coil with hot water. Changed the defrost setting from every 6 hours @30 minutes to 45 minutes 4x per day. Is that too long for freezer defrost????
Tech thinks that iced up coil could have given us low charge indications on the sight glass. He pulled out 20Lbs or so of gas but the system sight glass is still clear.
Also performed pump down test on copeland 6DT3-300E COMPRESSOR. COULD ONLY GET SYSTEM INTO 15 PSI VACUME WHILE THE OTHER UNIT PUMPED DOWN RATHER QUICKLY DOWN TO 25PSI.
BEFORE WE OPEN UP COMPRESSOR WE WANTED TO LET THE SYSTEM RUN A FEW DAYS WITH A ICE FREE CLEAR EVAPORATOR COIL BEFORE OPENING UP THE COMPRESSOR.
ANY HINTS WITH CHARGING 404A SYSTEMS? ANY ADDITIONAL HELP OR IDEAS WOULD HELP.
[Edited by hvacdoctor on 09-29-2004 at 11:49 AM]