AEC NEC Central Station Air and Water Cooled Chiller - Manual (Page 32)

NEC Series Water- and Air-Cooled Central Chillers Page 31
4-4 Crankcase Heater
NEC Series central chillers have a crankcase heater wired through the control transformer that
operates continuously whenever power is applied to the chiller.
Caution!
Energize the crankcase heater for 24 hours before initial startup
to drive dissolved refrigerant from compressor oil.
Failure to do so damages the compressor!
4-5 High Pressure Cutout
This electro-mechanical safety feature opens the control circuit if the system condensing
pressure exceeds a safe level.
High pressure cutout setting R-22 R-502
NECW water-cooled chillers 325 psi 325 psi
NECR air-cooled chillers 400 psi 400 psi
Note: The high pressure cutout is a manual reset control. Call a refrigeration service technician
to analyze the problem and to reset the control.
4-6 Low Pressure Cutout
This electro-mechanical safety feature prevents the evaporator temperature from dropping below
a preset point. The factory setting permits 20°F operation with a 70% water, 30% ethylene glycol
coolant mixture.
Type of refrigerant Opens control circuit @ Resets control circuit @
R-22 units 28 psi 70 psi
R-502 units 18 psi 57 psi