Water Cooled Chiller
"Water cooled chiller" means that the refrigerant in the condenser releases heat to water instead of air.
In addition to the chilled water loop, there will be another water loop in this system: a condensing water loop from the condenser, to a tower where the water will be cooled by evaporation, and then back to the condenser.
And a conscientious water quality program is absolutely essential to prevent scale, slime, and even corrosion inside the condenser.
If you don't have a water quality program in place, contact the manufacturer of your water cooled chiller, and a local water treatment professional if necessary.
If you're looking for some information about troubleshooting, our
Air Conditioning and Refrigeration System Evaluation Manual
has cycle diagrams for air and water cooled reciprocating chillers, a log sheet, and guidance on evaluating chiller pressures, temperatures, and operating characteristics.
Are you troubleshooting a Trane centrifugal water cooled chiller that's running with poor cooling capacity?
The following tips might help, if you don't have a good set of manuals for the machine, and can't get an experienced chiller technician to check it for you.
To check for air in the system, check the temperature of the liquid refrigerant at the upper liquid line well leaving the condenser, and compare it to the condensing temperature.
If the temperatures aren't within 3 degrees of each other, there are non-condensables in the system.
Condensing water delta t (temperature rise through the condenser) may look normal.
Check the purge system operation, and you might want to start checking for leaks.
Do you know what 'condenser approach' and 'evaporator approach' are?
Evaporator approach is the difference between evaporating temperature measured at the well in the evaporator, and leaving chilled water temperature.
Condenser approach is the difference between liquid refrigerant temperature as measured on the liquid line, and leaving condenser water temperature.
Normal condenser approach is 0 to 3 degrees.
If approach is 4° or more, it's an indication your water cooled chiller has fouled tubes.
If condenser approach is 4° or more and the condensing water delta t is low, it's an indication of non-condensables in the condenser, insulating the tubes and reducing heat rejection to the water.
With non-condensables, condensing pressure will be higher than normal.
Whether your water cooled chiller has a reciprocating, screw, or centrifugal compressor, If the head pressure is rising and your pumps, tower, and piping all seem to be ok, get a tube cleaning machine and gasket material ready, and don't hesitate to pull an end bell off to inspect the tubes and clean them if they need it.
Evaporator approach can be used to evaluate the refrigerant charge.
In a 1 pass evaporator, approach should be 10° to 14°.
In a 2 pass evaporator, approach should be 7° to 10°.
In a 3 pass evaporator, approach should be 3° to 6°.
Take all readings with the water cooled chiller at full load.
A higher than normal evaporator approach can indicate an undercharge.
A lower than normal evaporator approach can indicate an overcharge.
Evaluate all other operating characteristics.
Another condition you might be encountering with your centrifugal water cooled chiller is 'surging'.
This would be when the chiller makes a noise like a squealing elephant, and it indicates that there's a problem.
It happens when the difference between the evaporating temperature and condensing temperature exceeds design conditions, which is about 70 degrees.
When this difference, which is called lift, exceeds design conditions, refrigerant flow will reverse through the impellers, which causes the squeal, and can lead to other problems.
Surging can be caused by non-condensables, fouled condenser tubes, low condenser water flow, high entering condensing water temperature, and low refrigerant charge.
Surging can damage the thrust bearings and impeller, so if you hear your centrifugal water cooled chiller surging, find and correct the problem immediately.
I hope this page has helped, and please, feel free to contact us with any specific HVAC questions you might have, including questions about air conditioning on Guam, and refrigeration on Guam.
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