Data Aire LCS Installation, Operation And Maintenance Manual

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Data Aire LCS Installation, Operation And Maintenance Manual Manual pdf 22 page image

22the refrigerant tank and set it for liquid feed. Open the refrigerant tank valve and purge the line athe manifold. Open the high side valve on the manifold only and allow the refrigerant to flow untilthe system pressure equalizes. At this point the system will have 78 - 85% of the total refrigerantcharge. Start the (evaporator) blower. Start the compressor and check the operating pressuresand temperatures.A quick and easy way to run the blower and compressor is using the manual switches on the unitmicroprocessor. Switch the blower and compressor manual switches to the “ON” position. Allautomatic control is disabled but safety switches will remain functional.Before starting a compressor, the crankcase heaters should be energized for a minimumof 12 hours to reduce the possibility of liquid slugging on start-up. Failure to energizecrankcase heaters could result in compressor damage.Start the evaporator fan and verify the fan rotation. Start the compressor. Check the liquid line sightglass to get a feel for the approximate charge. Bubbles in the sight glass are not unusual at thispoint and can be caused by flashing from liquid pressure drop, low sub-cooling or low charge. It islikely that more refrigerant will be required to complete the charging procedure.If the receiver (head) pressure is below 230 PSI, block part of the condenser coil surface until thepressure rises to 230 PSI or higher. During extremely cold weather all the condenser fans may haveto be de-energized to maintain 230 PSI.Observe the sight glass on the receiver. Add refrigerant through the suction line until the level ofliquid in the receiver is approximately 1/3 from the bottom (the leveling ball in the receiver will startto float) of the sight glass. At this point the receiver is 80% full. Observing the receiver sight glassbecomes difficult when they are remote mounted near the condenser. The unit should be allowedto stabilize for several minutes before meaningful measurements can be taken.After the system is allowed to stabilize, the superheat at the compressor suction line (reading from atleast 6 inched from the compressor) should be 8 - 15°F. Unit with remote condensing units (DRCU)the superheat should be 20 - 25°F at the compressor. The sub-cooling will be the same 8 - 10°Fas a standard. Remove any block that may have been used on the condenser coil. If the ambienttemperature while charging is below 60°F, some of the refrigerant will be backed up in the condensercoil causing the liquid level in the receiver to drop, this is normal.Note: Charging to a full liquid line sight glass should never be the sole means ofdetermining the correct refrigerant charge. Other parameters such as superheat, suctionpressure, head pressure, sub-cooling and ambient temperature are also importantparameters. A system charged to a clear sight glass is often overcharged.5.3 Water/Glycol Cooled Systems5.3.1. Water/Glycol Cooled Systems ChargingAll water/glycol cooled units are factory charged with refrigerant. The water regulating valve shouldbe adjusted to maintain condensing temperature of 105 - 119° F. Saturated suction temperature