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# Error When Using Single Speed Cooling Tower in OS 1.5.1

I'm getting severe error when using single speed cooling tower which terminates the run. I'm not getting this error when using 2-speed and variable speed cooling towers. All auto sizable fields were left as autosized for all 3 types of towers but I'm getting errors only when using the single speed tower. Also, the edit tab for the single speed cooling tower shows grayed out fields (cannot be edited). Is there a way to make this fields editable?

Below is the error message I'm getting:

* Severe * CoolingTower:SingleSpeed "1 SPD COOLING TOWER". Tower performance input method requires valid nominal capacity.

* Severe * CoolingTower:SingleSpeed "1 SPD COOLING TOWER". Nominal tower capacity has been specified and design tower UA is being autosized.

* ~~~ * Design tower UA field must be left blank when nominal tower capacity input method is used.

* Severe * CoolingTower:SingleSpeed "1 SPD COOLING TOWER". Nominal capacity input method has been specified and free convection UA is being autosized.

* ~~~ * Free convection UA should be left blank when nominal tower capacity input method is used.

* Severe * CoolingTower:SingleSpeed "1 SPD COOLING TOWER". Free convection nominal capacity must be less than the nominal (design) tower capacity.

* Fatal * Errors found in getting cooling tower input. ...Summary of Errors that led to program termination: ..... Reference severe error count=4 ..... Last severe error=CoolingTower:SingleSpeed "1 SPD COOLING TOWER". Free convection nominal capacity must be less than the nominal (design) tower capacity.

I'm testing this on a simple model to isolate the error and get quick results. Nominal capacity can't be entered manually as the field and others are grayed out. Any comment on why this error is occurring or suggestions to correct this error will be most appreciated. Thanks.

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This is a bug in the library data. I added an issue to the bug tracker to fix it. Until that happens you have two options. You can use the "Packaged Rooftop VAV with Reheat" template, which will insert a valid single speed tower in the condenser loop. If you don't want all of the other stuff that comes with that template you can edit or remove it. The other option is to edit the library data directly by modifying the library file located in C:\Program Files (x86)\OpenStudio 1.5.2\share\openstudio-1.5.2\OSApp\hvaclibrary. If you search that file for "1 Spd Cooling Tower" you will find the object in question. Edit it so that it looks something like this:

OS:CoolingTower:SingleSpeed,
{6f622c95-b528-4dfc-bab0-e99c7cbea283}, !- Handle
1 Spd Cooling Tower,           !- Name
,                                           !- Water Inlet Node Name
,                                           !- Water Outlet Node Name
autosize,                               !- Design Water Flow Rate {m3/s}
autosize,                               !- Design Air Flow Rate {m3/s}
autosize,                               !- Fan Power at Design Air Flow Rate {W}
autosize,                               !- U-Factor Times Area Value at Design Air Flow Rate {W/K}
autosize,                               !- Air Flow Rate in Free Convection Regime {m3/s}
autosize,                               !- U-Factor Times Area Value at Free Convection Air Flow Rate {W/K}
UFactorTimesAreaAndDesignWaterFlowRate, !- Performance Input Method
,                                       !- Nominal Capacity {W}
0;                                      !- Free Convection Capacity {W}

more

Thanks for the answer Kyle. I tried first the second option and edited the hvac library as shown in your screenshot. I still got the same error message and lost the contents in the library tab, e.g., when I click the FCU sub tab, nothing appears. Perhaps I messed up the hvac library file when I did the edit. The first option worked for me although it involved a lot more editing work to remove the air loop, chilled water loop, and hot water loop for 8 cooling towers. I hope this feedback is useful. Thanks again.

( 2014-11-08 20:01:27 -0500 )edit