View Full Version : Dilution Anomaly in LiBr York Chillers YIA-ES5C3 vs YPC-ST400

23-05-2016, 11:10 AM
@ambient temperature=42Celsius, CoolingWater temperature=33Celsius
We have two York chillers both 400TR with following overview:

YIA-ES5C3 (early 90s model with manual controls) steam-fired, single stage, max 1.1bar steam@3.5ton/hr
YPC-ST400 (latest equipped with Millenium Control Center) steam-fired, double stage, max 7bar steam@1.8ton/hr


The question regards their dilution algorithm
In our ST400 model when chiller is on dilution both solution pump & refrigerant pump are on till our Generator pressure (on Millenium Centre) approaches ~5kPa.
In our ES5C3 model their is a three way knob, when chiller is on load it's turned to Normal, we can switch knob over to the Service mode if dilution required, the last setting is OFF while knob is in center. In dilution mode ES5C3 only activates solution pump, refrigerant pump is OFF this is the major difference in ES5C3 and ST400 model. A timer in ES5C3 will ultimately tell operator when to quit dilution.

ST400 is our main cooling unit, ES5C3 is a backup plan. Our operators are accustomed in dealing with ST400, for instance even if ST400 is on load (cooling sequence initiated) we can put the machine in fake dilution by turning off manual steam valve upstream of chiller's steam control valve because the end result of this is dilution even though machine thinks its on load! We applied same procedure to ES5C3 but we experience a problem!

The upstream manual steam valve was turned off, while ES5C3 steam control valve was open ..Generator temperature started decreasing & machine was put to fake dilution but both pumps (solution/refrigerant) were on. When generator temperature approached ~50celsius and the side glass at absorber was almost flooded (its level is ~30% when ES5C3 is on load @Generator temperature 85Celsius) we put the knob in center & machine turned off. The problem occured at next startup of ES5C3 when the panel indicated low refrigerant level & refrigerant pump fails to initiate. The refrigerant pump starts then automatically turn off & this sequence kept repeating, till we provided some steam ~0.5bar & a while after we acquired normal operation. Seeminlgy the provided steam at generator provided vapours for condenser to ultimately provide refrigerant to the pump. I know as shown in first figure Unloader Control Valve will open in case of low refrigenart level where some of the solution will be charged into refrigerant reservior but this we avoided by tinkering with valve's supply. it may be a bad idea but I want to avoid refrigerant polluting.

My question regarding ES5C3 is why in the first place refrigerant level gets emptied after all both pumps keep online while dilution ST400 model. Theoretically even if refrigerant pump keep online during dilution it shouldn't effect refrigerant level until refrigerant tray (in evaporator) has developed some holes...Assuming the internals of ES5C3 are in good health why officially putting this machine on dilution (Service mode) only activates solution pump & not the refrigerant pump?