Why is the Glycol Chiller set to -4°C (24.8°F) / -4.5°C (23.9°F)
The Glycol Chiller is set to keep the glycol at -4°C (24.8°F) / -4.5°C (23.9°F).
This will not freeze over as glycol can go down to -15°C (5°F) before its starts to freeze. The compressor on the chiller only kicks in when the glycol is too warm and works like a fridge.
The reason for the extra cool glycol is so the cooling works efficiently. If it was glycol was only at 7°C (44.6°F), then the cooling would take longer and be less efficient for rapid cooling.