BUBBLES IN SIGHT GLASS

[dukes13]

Is it possible to have a correct charge and still have bubble in the sight glass? 8ºSH, 10º SC, R-22

[toocoolforschool]

Yes, especially with mixed refrigerants txv's and high loads.

[dukes13]

What do you mean?

especially with mixed refrigerants txv's?

[SBKold]

Bubbles in glass while sc is measured indicates noncondensibles.

[mikeacman]

Possible non cons ....

Do you have condensor fan cycling for head pressure control?

This can also occur when the fan comes on after being off and is normal....

[toocoolforschool]

What do you mean?

especially with mixed refrigerants txv's?

did I studder?

[dukes13]

evacuate system down to 445µ!
+

Possible non cons ....

I jumped the switch to operate continuously,
Do you have condensor fan cycling for head pressure control?

This can also occur when the fan comes on after being off and is normal....

NO mixed refrigerants.

especially with mixed refrigerants txv's?

[2sac]

did I studder?

Stuh-stuh-stuh-studder

[joeblo]

R-22 is not a mixed refrigerant. Subcooling is the cooling after in has become 100% liquid (no bubbles). I would check to make sure your readings are correct and possibly a restriction before the sight glass.

[alcomech]

What is the tonnage for this system.
Is this a split system and if so how long is the line set.
What is the the size of the liquid line and the suction line.
Where is the sight glass located, is it at the condenser or at the evaporator.
Does this system use a TXV.
What is the suction pressure.
What is the head pressure, out door ambient temperature, and indoor temperature.
Where are you measuring super heat, at the evaporator or at the compressor.
If you are measuring at the compressor, why is the superheat so low.
Have you verified correct air flow.

Like Mikeacman asked, what are you using for head pressure control.

The presence of flash gas or bubbles in the sight glass is not an accurate indication of non condensables in the system. For this you will need to identify all other probabilities first. Such as a low ambient condition and cycling of condenser fan motors. You must raise your head pressure to around somewhere in the range of at least 200 PSIG or 105 deg liquid saturation temperature first............

_______________________________
Trouble shooting is not part of the repair.......understand the symptoms and you will find the solution.

[jpsmith1cm]

What is the tonnage for this system.
Is this a split system and if so how long is the line set.
What is the the size of the liquid line and the suction line.
Where is the sight glass located, is it at the condenser or at the evaporator.
Does this system use a TXV.
What is the suction pressure.
What is the head pressure, out door ambient temperature, and indoor temperature.
Where are you measuring super heat, at the evaporator or at the compressor.
If you are measuring at the compressor, why is the superheat so low.
Have you verified correct air flow.

Like Mikeacman asked, what are you using for head pressure control.

The presence of flash gas or bubbles in the sight glass is not an accurate indication of non condensables in the system. For this you will need to identify all other probabilities first. Such as a low ambient condition and cycling of condenser fan motors. You must raise your head pressure to around somewhere in the range of at least 200 PSIG or 105 deg liquid saturation temperature first............

_______________________________
Trouble shooting is not part of the repair.......understand the symptoms and you will find the solution.

This is the best answer.

[Tool-Slinger]

Is it possible to have a correct charge and still have bubble in the sight glass? 8ºSH, 10º SC, R-22

Generally speaking a TXV requires liquid to operate correctly.

But as for having bubbles with a given SC, yes it happens. The refrigerant is in motion inside a working system, not like on a work-bench where 1 degree SC=pure liquid. I generally work on RTUs and do not get a clear and reliable sightglass until around 16 SC.

[ryan1088]

Generally speaking a TXV requires liquid to operate correctly.

But as for having bubbles with a given SC, yes it happens. The refrigerant is in motion inside a working system, not like on a work-bench where 1 degree SC=pure liquid. I generally work on RTUs and do not get a clear and reliable sightglass until around 16 SC.

I've seen this on chillers with subcoolers on them. Seems like on those you get about 12 degrees before the thing clears. The first time I saw it I actually had 2 thermometers on there just to make sure I wasn't crazy.