[Ellantra]

Good day!
I came across certain procedure in York Chiller O&M manual (160.54-O2) about "Checking the Refrigerant Charge During Unit Shutdown".

Accordingly, "....the refrigerant charge should always be checked and trimmed when the system is shutdown. The refrigerant level must be checked after the pressure and temperature have equalized between condenser and evaporator. This would be expected to be 4 hours or more after the compressor and water pumps are stopped. THE LEVEL SHOULD BE VISIBLE IN THE SIGHT GLASS...."

However, when i checked our standby Chillers (YK - 2400 TR with refgt charge of 3,042 kgs), the refrigerant level is not visually seen thru the sight glass. Does this means, insufficient charge???? or is the written procedure irrelevant??? The fact that we have added refrigerant from 2,846 kgs to 3,042 kgs, i was expecting the liquid refrigerant level can now be seen through sight-glass of the chiller while they are shutdown.

I have spoken to the local chiller technical guy of JCI. According to him, when the chiller is shutdown, this refrigerant level is insignificant. However, I thought of seeking opinion who has experienced the same concern through this forum to better understand why it was written but not being followed.

I understand that the refrigerant level in the sight glass does not guarantee 100% the correct refrigerant charge/weight. However, it is useful to track the level by monitoring it periodically to identify losses which would result to poor efficiency if not detected.

 

[jayguy]

Is the Evaporator a “Falling Film” style?

 

[Chev5372]

Could be the level is above the sight glass. If your gas is oil free or has been off for a while the oil could have settled out. Try shining your flashlight up thru the sight-glass and it may reflect off the level giving you an idea if the gas is above.
If the condenser is 10-15 degrees above the evaporator a good portion of the gas may be over there, check the condenser sight-glass.
If you have other chillers on line try flowing some of that water thru the idle chiller and watch the evaporator sight-glass gas will come over and you met see “ heat waves” in the liquid.
Falling film style chiller the gas could be in both heat exchangers, get it to move by flowing chilled water , the gas will collect in the evaporator.


Sent from my iPhone using Tapatalk

 

[Ellantra]

Thanks for the quick feedback Chev5372 and Jayguy. Our chillers are YK model with conventional flooded evaporator. We have tried using a flash light but still the level is not visible. What we did to confirm was, we In fact, we put some water flow thru the evaporator and started seeing the liquid refrigerant going up like "heat wave" thru the sight glass. This confirm, that the liquid refrigerant is below the evaporator sight glass.

Since the orifice is open when the chiller is off and the evaporator and condenser pressure are equal, i was expecting that that refrigerant level would equalized and visible in the evaporator sight glass after 4 hrs as mentioned in the York YK chiller O&M manual.

Would this mean something or just a normal condition?

Tracking the level by monitoring it periodically helps us identify refrigerant loss which would result to poor efficiency if not detected.

 

[ehsx]

Thanks for the quick feedback Chev5372 and Jayguy. Our chillers are YK model with conventional flooded evaporator. We have tried using a flash light but still the level is not visible. What we did to confirm was, we In fact, we put some water flow thru the evaporator and started seeing the liquid refrigerant going up like "heat wave" thru the sight glass. This confirm, that the liquid refrigerant is below the evaporator sight glass.

Since the orifice is open when the chiller is off and the evaporator and condenser pressure are equal, i was expecting that that refrigerant level would equalized and visible in the evaporator sight glass after 4 hrs as mentioned in the York YK chiller O&M manual.

Would this mean something or just a normal condition?

Tracking the level by monitoring it periodically helps us identify refrigerant loss which would result to poor efficiency if not detected.

In all cases, charge should be verified at design operating conditions. Order spec sheet should list expected operating conditions. Nameplate weight & sight glass off level are typically calculated and may vary slightly.

 

[jayguy]

…What we did to confirm was, we In fact, we put some water flow thru the evaporator and started seeing the liquid refrigerant going up like "heat wave" thru the sight glass. This confirm, that the liquid refrigerant is below the evaporator sight glass….

You saw an invisible vapor in the sight glass? What you likely saw was a change in density in the liquid.

I understand what you are trying to do. Unfortunately, due to changes in temperature and pressure (which affects the density), you are not likely to have the same refrigerant level from year to year and be able to make a judgement call on whether there is enough refrigerant in the system.

If you were to find the system radically low, you would pull the charge and weigh it during the off-season anyway. If it is your only chiller and/or its performance is critical, then I recommend stocking some refrigerant on site or pulling the charge and weighing it.

During my Shutdown Inspections, I do make a note about the refrigerant level in the sight glasses. But it is more about me looking to see what I see such as debris in the sight glass or the color of the refrigerant (yellow/brown my indicate an excess of oil). If I see a radically different refrigerant level, then I make a note and let the customer decide what they want to do. The best refrigerant volume prediction is based on performance as mentioned.

 

[jwalkington]

Good day!
I came across certain procedure in York Chiller O&M manual (160.54-O2) about "Checking the Refrigerant Charge During Unit Shutdown".

Accordingly, "....the refrigerant charge should always be checked and trimmed when the system is shutdown. The refrigerant level must be checked after the pressure and temperature have equalized between condenser and evaporator. This would be expected to be 4 hours or more after the compressor and water pumps are stopped. THE LEVEL SHOULD BE VISIBLE IN THE SIGHT GLASS...."

However, when i checked our standby Chillers (YK - 2400 TR with refgt charge of 3,042 kgs), the refrigerant level is not visually seen thru the sight glass. Does this means, insufficient charge???? or is the written procedure irrelevant??? The fact that we have added refrigerant from 2,846 kgs to 3,042 kgs, i was expecting the liquid refrigerant level can now be seen through sight-glass of the chiller while they are shutdown.

I have spoken to the local chiller technical guy of JCI. According to him, when the chiller is shutdown, this refrigerant level is insignificant. However, I thought of seeking opinion who has experienced the same concern through this forum to better understand why it was written but not being followed.

I understand that the refrigerant level in the sight glass does not guarantee 100% the correct refrigerant charge/weight. However, it is useful to track the level by monitoring it periodically to identify losses which would result to poor efficiency if not detected.

I found a york that a customer was experiencing symptoms with sight glass appeared empty. Found that the sight glass was actually so full it just looked empty.

 

[Ellantra]

Hi jwalkington..thanks for the feedback. We have done the inspection diligently with my colleagues, i don't think this is otherwise. In fact, we actually saw some of our chillers where the refrigerant liquid is just below the sight-glass but not within the sight-glass level. I can share a video clip of what we did after putting water flow in the evaporator where the refrigerant level increase gradually.

My point here is..... Is this a normal condition having the liquid refrigerant not visible in the evaporator sight-glass? Or Is this another sign of problem (refrigerant leak, incorrect charge, etc)? Appreciate to hear your experience. Thanks

 

[Ellantra]

Hi jayguy....thank for the reply once again.... Agree with you, weighing the the refrigerant is the best measure to quantify the amount of refrigerant in the system. The process of doing this takes a lot of time and resources plus the expected refrigerant loss of about 100kgs during the process. I was trying to propose a proactive means to our management ensuring our chillers are having enough refrigerant before the summer starts as DC provider.

After seeing this procedure in York Chiller O&M manual (160.54-O2), i thought of implementing it. However, based on your experience, the presence of liquid in the sight-glass is being used to determine the quality....

On the other hand, doing the performance test, it requires certain design conditions, however, it may not be practical during winter period (where we are now) specially when the cooling demand is less.
This is our dilemma. Our opportunity to do the chiller maintenance is only before summer considering the number of chiller as well. Doing a performance test during summer for some chiller may be too late as proactive measure...

What about the condenser and evaporator pressure when they are equalized 4 hours before taking the liquid refrigerant level. Would this mean something? Considering that we are comparing our chillers with the same environment condition.

Lastly, in your opinion, why do you think York being the chiller maker wrote this procedure but not actually useful? Would you recommend to delete it?

Thanks again.

 

[jayguy]

some things in manuals (not just York) are "cut and paste" from many years ago. i know of some literature that is over 5 years old with cut and paste errors that haven't been updated yet. it happens. also, it used to be that ALL centrifugal chillers were designed for a 10F (5.55K) chilled water temperature drop. everything was the same. every evaporator was a flooded style system. same. same. same.

today, we have a varied temperature drop from chiller to chiller. i have a plant that have 2 chillers in series...same model number...same compressors...but because they operate at a different set of pressures/temperatures, they have different refrigerant charges even though the volume inside the chiller is exactly the same. some chillers have a falling film type of evaporator. some have isolation valves within the chiller that may cause the refrigerant to stack in different parts of the chiller. different. different. different.

sure, you can use the sight glass to measure the refrigerant level from year to year but i wouldn't necessarily put a lot of stock into it. the refrigerant level would have to be dramatically different before i would call a problem and even then, i would investigate it heavily first.