AEC NEC Central Station Air and Water Cooled Chiller - Manual (Page 31)

Page 30 NEC Series Water- and Air-Cooled Central Chillers
4-3 Freezestat Control
Figure 15
The freezestat shuts down the compressor if the chilled water temperature approaches the
freezing point. The chilled water pump on the system should continue to run.
It is factory set at 40°F or 10°F below the rated capacity operating temperature of 50°F (10ºC).
If lower chilled water temperatures are desired, the process water must be mixed with industrial
(not automotive) grade ethylene or propylene glycol with rust inhibitor to provide protection
down to 20°F below the desired operating temperature. Figure 15 shows the proper mixtures
needed to provide protection to 20°F below the desired operating temperature. The freezestat
cutout temperature can then be reset to a temperature 10°F below the desired operating
temperature.
Caution!
Only a qualified refrigeration service technician
should adjust freezestats.
The AEC, Inc. product warranty does not cover system freeze-ups!
Figure 15
Freezing Protection Curve