Liquid sight glass flashing

[irish_man]

Multi compressor rack using copeland scrolls, liquid receiver is more than half full which is 150l, but every so often I get liquid flashing through the main liquid line sight glass.
I changed liquid distribution header with liquid exit bottom and fitted sight glasses to both liquid line.. same thing, flashing at sight glasses and receiver is half full... any suggestions??

[Brian_UK]

Undersized liquid lines?

[irish_man]

Undersized liquid lines?

All the pipe calculations done using micro calc software.

[irish_man]

Is it possible that the main liquid pipe out of receiver tank is too small ? My 2 liquid stubs are 1 -3/8 & 1- 1/8, main pipe from receiver tank is only 1- 3/8..

[Neddy]

What Refrigerant is it? What's the liquid temperature and pressure?

[irish_man]

R507, 42 degrees liquid temp condensing pressure 280psi

[chemi-cool]

You might have condensing problems from high ambient or non condensable gas in the system.

[irish_man]

You might have condensing problems from high ambient or non condensable gas in the system.
Absolutely not, ambient here is average 35 degrees, I did triple vac and had 600 microns before adding refrigerant.

[HVACRsaurus]

Hi Mate,

I've seen something similar - in my instance was happening when the condenser fans were cycling (ON 60 seconds / OFF 60 seconds etc. operated by pressostat)

The "falling" pressure versus to the thermal inertia of the refrigerant caused it to boil at the bottom of the swing.

Confirmation was made by locking on a suitable number of condenser fans but locking out remainder, (no cycling = no boiling)

Happy hunting!

[irish_man]

Hi Mate,

I've seen something similar - in my instance was happening when the condenser fans were cycling (ON 60 seconds / OFF 60 seconds etc. operated by pressostat)

The "falling" pressure versus to the thermal inertia of the refrigerant caused it to boil at the bottom of the swing.

Confirmation was made by locking on a suitable number of condenser fans but locking out remainder, (no cycling = no boiling)

Happy hunting!

Fans are controlled via electronics and minimum on/off at 5 seconds. I don't think that's the issue here. But I'll try lock on a number of fans and try your theory. Thanks

[Goober]

Could be just the loads/solenoids/EPR's energizing throughout the system? Momentary drop in liquid pressure and liquid lines flash. Nothing I would really worry about.

[AndyHX]

I agree with Hvacsaurus , multi fan condensers on pressure switches with minimum of 15 psi differential cause a fluctuation of liquid pressure and liquid rises and falls in liquid line. EC fans on 0-10v beautiful.

[Glenn Moore]

Hi
I agree with Andy and HVac any type of condenser fan cycling will cause bubbles in the sight glass, also check your expansion valves superheat settings and make sure they are not "hunting" as if one or more of the TEVs are hunting this can also cause bubbles in the glass . Check and adjust them as necessary, even one with a partial loss of charge in its power assembly can cause this problem