REFRIGERANT CARRY OVER

[low pressure guy]

Hey, can someone tell me how identify refrigerant carry over on Trane Centra-vacs

[absrbrtek]

Low discharge superheat.
Originally posted by low pressure guy
Hey, can someone tell me how identify refrigerant carry over on Trane Centra-vacs

[psychometric]

I've only had that problem when my condenser water temp was too low. check that out. Mahoney taught me that, he's a master with centri-vac's

[scott123]

Cold condenser water temperature will cause refrigerant stacking within the condenser. This condition will be unlikely to cause cary over, in fact it would help reduce it, if a machine was overcharged.

Caryover can be caused by several factors.

If the chiller is off for some time with chilled flow, most of the refrigerant would be stacked in the evaporator. Upon start up, caryover could occur for a period of time until the excess refrigerant has been moved over to the condenser.

Low chilled water flow can cause caryover

Refrigerant overcharge can cause caryover.

Caryover can occur during chilled loop pull down

Those are some of the examples of conditions that can lead to refrigerant caryover.

[overhaulin]

CARRYOVER IS LOW DISCHARGE TEMPURATURE, DISCHARGE SUPERHEAT........ CAUSED BY OVER CHARGE........SOME CHILLERS WILL CARRY OVER ON PULL DOWN BECAUSE THEY ARE TRYING TO MAINTAIN SUBCOOLING. THE NORMAL TEMP'S ON THE DISCHARGE ARE 90 TO 100 DEGREE'S ON 123 AND 125 TO 135 ON
R-11. 90 TO 100 ON 134A AND R-12 500 125 TO 135 @ 100% LOAD. BOTTOM LINE LOW DISCHARGE TEMP. IS OVER CHARGED.

[scott123]

Low discharge temperature can be caused by many other factors. More often then not (on large chillers) carryover is not a result of being overcharged.

[overhaulin]

I beg to differ, refigeration cycle is pressure's and temp. The other issuses are engineering design,we can change a lot of things but we can't change the law of physics. As far as large tonage chiller's you will see the same thing. Take the duplex cvhf extended cap. tubes leaking refrig. from one vessle to the other, low on one side over charged on the other. 3000 ton's. Oh sure measure the level. Discharge temp is high on one side and low on the other.Is this big enough or are you talking larger tonage?

[chiller mekanik]

Looks like most of us agree that low DSH is a result of carry over.
Is this an accademic exercise or are we trying to help you solve a problem?
If its a real problem, give us some more info, what kind of trouble are you having?

[scott123]

Originally posted by overhaulin
I beg to differ, refigeration cycle is pressure's and temp. The other issuses are engineering design,we can change a lot of things but we can't change the law of physics. As far as large tonage chiller's you will see the same thing. Take the duplex cvhf extended cap. tubes leaking refrig. from one vessle to the other, low on one side over charged on the other. 3000 ton's. Oh sure measure the level. Discharge temp is high on one side and low on the other.Is this big enough or are you talking larger tonage?

Not sure what you're trying to say. Been at Trane 15 years and have 11 Duplex chillers under contract. None of these chillers ever had one circuit leak to another. Anyone do a baseline where you live to insure the tubes are fine before charging?

Caryover can and will occur, but the reality is it occurs due to operating conditions far more often then being overcharged. Low DSH is simply a result of caryover just like a 3 ton package unit.

[maxster]

THE NEWS has a big artical this week on carryover-stacking on chillers you can view a digital copy http://www.achrnews.com page # 22 in the issue for July 3rd isn't up as of yet give it a day to be current

[Edited by maxster on 07-05-2006 at 08:37 PM]

[chillerguru]

can not log in please send me digital copy @ chillerguru@sbcglobal.net

[scott123]

I’m still trying to understand what is so complicated about carryover, and what symptoms cause it. It is rather easy to diagnose.

[r404a]

How about an oil logged evap or fouled evap tubes.....



r404a

[scott123]

Fouled evap tubes (depending on machine) can cause caryover, but usually you will limit on evaporator refrigerant temp. Another symptom of a fouled evap will be a reduced or inverted condenser approach.

Oil logged machines have a tendency to limit on evap, but also pulsate to some degree as the oil is passed through the compressor. I had a machine that was so oil logged it tripped on locked rotor overload above 50%. After distilling the refrigerant I found the machine overcharged by 50 gallons of oil.

In both of these cases caryover is a symptom but on newer machines with good local controls it will be limited.