Carrier 30GTN100 chiller

[technic76]

I just inherited a carrier model# 30gtn100 This unit has two sight glasses. One is located right after a two core liquid line drier and the second is located in part of the EXV’s body. The first sight glass does not flash at all and always has a full column of liquid no matter how many compressors and fans are running. The other sight glass that is located in the exv’s body constantly flashes and never runs a full sight glass. I’m just curious of the purpose of the second sight glass. The sight glasses are less than three feet apart.

[Sicofthis]

Not sure but I would guess its to visually check exv position.

[ga1279]

Like Sicofthis said it is a visual check, If you were to see a full sight glass you would have some thermodynamic problems. The constant "flashing" you are visualizing is some of the liquid refrigerant boiling off the heat from the rest of the liquid so it gets cold enough to absorb the heat from the water passing through the chiller barrel. Remember you have a pressure differential across the valve the causes the temperature differential. -GEO

[Dallas Duster]

Flashing usually happens after the metering device like you are experiencing. The sightglass on the valve is the check EXV operation.

[technic76]

Thanks for the info, I was thinking that the refrigerant was already passing through a metering device and boiling off but I wasn't sure. I have never taken one of these EXV's apart and I wasn't sure how they operate.