Minimum Inputs for VRF System

asked 2020-09-08 18:05:16 -0500

Draza's avatar

updated 2020-09-11 08:05:18 -0500

I'm trying to better understand how the VRF system is modeled. I'm using openstudio 3.3.0. I built a "Test Model" whos geometry is a simple two room floor plan, each room is its own thermal zone.

After placing the VRF system and the VRF Zone Terminal Units, I get the following error when running the simulation.

Fatal ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. Preceding condition(s) causes termination.

I went through and tried to enter information into the input fields that were blank, but the error persist.

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"Preceding condition(s) causes termination." Are you sure there isn't more information in the .err file that indicates the problem in more detail?

shorowit's avatar shorowit  ( 2020-09-09 10:41:42 -0500 )edit

After reading though it in more detail, it mentioned that the minimum value of x for the two OS::Curve:Cubic that define the Cooling and heating Energy Input Ratio Modifier Function for Low Part Load Ratio Curves was 0.5. This was out of the acceptable boundary. It had to be <= the minimum heat pump part load ratio, which was defined as0.25 as default. I changed both values (blindly without really understanding what they mean) and the simulation was able to run. After reading through the input output reference, I was able to get a better understanding of how the heat pump part load ratio is

Draza's avatar Draza  ( 2020-09-09 11:53:13 -0500 )edit

used, but I couldn't find anything on how the coefficient of the different curves and their x and y boundaries are found.

Draza's avatar Draza  ( 2020-09-09 11:54:28 -0500 )edit

I don‘t have the reference handy, but if you search for VRF or VRV and Raustad and FSEC, you ought to be able to find THE reference document for how to generate those curves.

mattkoch's avatar mattkoch  ( 2020-09-13 07:55:13 -0500 )edit