moister indicator and sight glass

[dan wong]

On Sporland sight glass with moister indicator; Normally; green = Dry, yellow = wet.

I had a air condition system where moister indicator turned yellow -which is wet. I removed the *****, evacuated the system to 300 micron. I was expecting yellow would return to green - nop - it stay yellow - very faint green.

My question:
1) Does moister indicator return to green after deep vaccuum?

[chemi-cool]

Moister indicators don't just turn yellow, there is a reason for that.

Do you have any reason to suspect that moister have entered the system?

If the indicator in direct sun light, it will go bad.

Why not replace it?

[dan wong]

Moister indicators don't just turn yellow, there is a reason for that.

Do you have any reason to suspect that moister have entered the system?

If the indicator in direct sun light, it will go bad.

Why not replace it?

there is no leak on system. it is not exposed to direct sun light. Since it turn yellow, I assume it was wet. Yes, I will replace the sight glass - Later.

For now; I am interested answeres. Does it ever return to green? at what vacuum level? Does that chemical change over time? If no moister in the system - does it stay green forever?, Once it turn yellow, does it stay yellow forever?

[chemi-cool]

there is no leak on system

So? How can moister get in?

Does it ever return to green? at what vacuum level? Does that chemical change over time? If no moister in the system - does it stay green forever?, Once it turn yellow, does it stay yellow forever?

You will have to address these questions to the moister indicator manufacturer.

My philosophy says: When there is a doubt - there is no doubt.

replace it and see.

[paul_h]

there is no leak on system. it is not exposed to direct sun light. Since it turn yellow, I assume it was wet. Yes, I will replace the sight glass - Later.

For now; I am interested answeres. Does it ever return to green? at what vacuum level? Does that chemical change over time? If no moister in the system - does it stay green forever?, Once it turn yellow, does it stay yellow forever?

I've seen them change before, but that's good condition, not so old ones. I think age and how long they've been yellow play a part in if they change back or not.
Yes I seen them change colour back after a good evacuation. They are often supplied loosley capped showing the moisture colour and change after install and evacuation.
If you've got a system without a leak and hasn't changed after a 300 micron vacuum, it's due to some moisture or sunlight maybe being present for a long time, and it's gone yellow and its likely it isn't going to go back to green.
They don't normally go yellow in a moisture free system just due to age, I've seen plenty of perfectly good 10 y/o ones.
But something has happened to the one you are looking at, and it seems stuck in the colour.

[dan wong]

I've seen them change before, but that's good condition, not so old ones. I think age and how long they've been yellow play a part in if they change back or not.
Yes I seen them change colour back after a good evacuation. They are often supplied loosley capped showing the moisture colour and change after install and evacuation.
If you've got a system without a leak and hasn't changed after a 300 micron vacuum, it's due to some moisture or sunlight maybe being present for a long time, and it's gone yellow and its likely it isn't going to go back to green.
They don't normally go yellow in a moisture free system just due to age, I've seen plenty of perfectly good 10 y/o ones.
But something has happened to the one you are looking at, and it seems stuck in the colour.

Excellent answere. Just what I suspected. My experience is just as you described. I been in this trade 28 years, I have see this happen several times, never figure out why, never got a satisfatory answere. They all say "Change it" which is what I normally do. Before I retire, I like to know "WHY?", your reply confirm my suspicion. Now, my brain can take a rest.
Something about me. When I don't understand something, It bother me a lot unit I find an answere. Just me I guess.

[NH3LVR]

Sounds like a good time to bring up something I have seen in the past.
Several years ago I saw three systems that had "Milky" sight glasses, in the same location. They were built by Bohn. Two 30 HP Copelands on each. Low temp duty. Looking through the literature I saw a recommendation to "Consult the manufacturer" if this occurred.
Several years later I ran across these same units. They had been installed in a different plant. The sight glasses were still obscured. I removed the moisture indicating portion through the bottom. I used a cotton swab to clean the glass. The milky substance never came back.
Does anyone know what could cause this?

[paul_h]

I've seen that too, like the sightglass gets dirty from the inside. My only guess is that it is desicant from the drier staining the glass, kinda of like when you change a water filter you get a bit of milky water for a while. Obviously not as much loose material come of a refrigerant drier, but you do get a bit of loose powder when removing a drier core from the tin.