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All water/glycol cooled units have a water regulating valve. A head pressure transducer is connect-
edtoaShraederttingonthedischargelineandwaterisregulatedintothecondensercoil(plate
ncondensersarestandard).
Before starting a compressor, the crankcase heater should be energized for a minimum
of 12 hours to reduce the possibility of liquid slugging on start-up. Failure to energize the
crankcase heater could result in compressor damage.
Note: Charging to a full liquid line sight glass should never be the sole means of deter-
mining the correct refrigerant charge. Other parameters such as superheat, suction pres-
sure, head pressure, sub-cooling and ambient temperature are also important. A system
charged to a clear sight glass is often overcharged.
4.4 Refrigerant Handling
The use of recovery/recycling units is required by U.S. Environmental Protection Agency (EPA)
regulations. Technicians who service and dispose of air conditioning and refrigeration equipment
must recover the refrigerant instead of venting it to the atmosphere.
Except for extremely small releases of refrigerant such as what occurs when disconnecting service
hoses, a technician who knowingly releases or vents refrigerant to the atmosphere is in violation of
thisregulation.RefrigerantpurchasersmustbecertiedtechniciansandhaveavalidEPAcertica-
tion card.
Warning! Pressure relief lines(s) must be vented to the atmosphere per the latest edition
of ASHRAE Standard 15 and/or any local building, re or mechanical codes.
This applies to all units with either sell and tube condensers or high pressure relief valve
options.
4.5 Important Refrigeration Components
4.5.1 Expansion Valve
Each refrigerant circuit has an adjustable thermo expansion valve (TXV). These are factory ad-
justedtotheirnormalrating.Anyeldadjustmentshouldbeto“netune”asystemthathasstabi-
lized and already has acceptable operating parameters. Adjusting a TXV to produce large swings
in superheat is not recommended.
4.5.2 High Pressure Cutout Switch
Each refrigerant circuit is protected by a high pressure cutout switch with manual reset button. The
switch is typically located in the evaporator near the compressor.
The high pressure rating for R-410A is 610 PSIG. The high pressure rating for R-407C is 450 PSIG.
4.5.3 Low Pressure Cutout Switch
Each refrigerant circuit has a low pressure cutout switch with automatic reset. The switch is located
near the compressor.
The low pressure for R-410A is 50 PSIG. The low pressure rating for R-407C is 28 PSIG.
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