Q: I have a new HMI sight glass right out of the box that is showing a wet condition. Can I use this in my system and will it give the proper moisture indication?
The element in the sight glass senses the moisture of the atmosphere that it is in. In this case, the air has enough moisture to turn the sensing element pink (wet). Once a sight glass is put into an operating refrigeration system, it will over time adjust its color to indicate the moisture level of the refrigerant. This change can take several hours to occur…it will not happen instantaneously.

Q: If I pull a vacuum on the system with the wet sight glass, will that change its color back to dry?
Pulling a vacuum by itself will not remove enough moisture from the HMI indicator to effect a color change in a short period of time. The recommended procedure is to install the HMI in the system with a new EK filter drier and clean, dry refrigerant, and operate the system. Within several hours the indicator will show the moisture condition of the refrigerant. It is recommended however, to allow the system to operate for 12 hours to attain complete quilibrium.