My question involves a dual-circuit packaged air-cooled chiller with four scroll compressors. One circuit looked fine. The other circuit sight glass was black on the moisture indicator. Rust could be seen inside the sight glass.
My first impression was that the system had contaminants and there was moisture in it. This is a new system that has not been started. I called the manufacturer’s representative and was informed that sunlight can cause this. The protective covers were on each sight glass.