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Cooling Coil Controller Error When Using Temperature Reset for Chilled Water Setpoint

asked 2016-04-27 21:40:39 -0500

jdunn gravatar image

updated 2017-05-17 12:22:20 -0500

I've been trying to tighten up my baseline model before submitting to LEED, and wanted to dig into a severe error that might raise some flags. The model is of a large k-12 school, and I'm using the HVACTemplate:System:VAV setup with a water-cooled chiller. I'm getting a controller error for the cooling coil that basically says the function is wrong (Reverse) and that the controller-sensed temperature is above the setpoint (see error language below).

Now the weird thing is, by comparing my file to the HVACTemplate-5ZoneVAVWaterCooled.idf example file, I was able to identify the input that causes the severe error. If you change the Chilled Water Setpoint Reset Type to outdoorairtemperaturereset in the HVACTemplate:Plant:ChilledWaterLoop, this creates the error. What was even stranger is that while in the example file it does not use temperature reset for its chilled water loop template object, it does fill in the temperature setpoint and outside air high and low fields. When I switch their reset from none to outdoorairtemperaturereset, it gets the same error controller error!

So my questions are:

  1. Why doesn't the "outdoorairtemperaturereset" for the chilled water loop in the HHVACTemplate-5ZoneVAVWaterCooled.idf example file work?
  2. Is it a problem the LEED reviewer will make me fix before proceeding (because all baseline models need to model chilled water outside air temperature reset).
  3. Is the fix the same for my model? Here's a link to the .idf and error file.

Thanks for any help!

   ** Severe  ** FindRootSimpleController: Controller error for controller = "VAV SYS 1 COOLING COIL CONTROLLER"
   **   ~~~   **  Environment=New Orleans Lakefront Ap LA USA TMY3 WMO#=722315, at Simulation time=01/14 19:45 - 20:00
   **   ~~~   **   Controller function is inconsistent with user specified controller action = Reverse action
   **   ~~~   **   Actuator will be set to maximum action
   **   ~~~   ** Controller control type=Temperature
   **   ~~~   ** Controller temperature setpoint = 11.82 [C]
   **   ~~~   ** Controller sensed temperature = 12.17 [C]
   **   ~~~   ** Controller actuator mass flow rate set to 1.26 [kg/s]
   **   ~~~   ** Controller actuator temperature = 12.20 [C]
   **   ~~~   **   Note: Chilled water coils should be reverse action and the entering chilled
   **   ~~~   **         water temperature (controller actuator temperature) should be below the setpoint temperature
   **   ~~~   **   Note: Hot water coils should be normal action and the entering hot
   **   ~~~   **         water temperature (controller actuator temperature) should be above the setpoint temperature
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answered 2016-04-28 22:50:35 -0500

The issue appears to be that the chilled water temperature is not BELOW the coil entering air temperature. I suggest a detailed investigation of the plant supply water temperatures. Specifically, why is the chilled water temp greater than the coil entering air temperature?

Controller temperature setpoint = 11.82 [C]  
Controller sensed temperature = 12.17 [C]
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Asked: 2016-04-27 21:40:39 -0500

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Last updated: Apr 28 '16