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# EnergyPlus VRF Piping Correction Factor Curve & Coefficient for Heating

For the EnergyPlus object AirConditioner:VariableRefrigerantFlow I can't find an example in the InputOutputReference or in the example files where the Piping Correction Factor for Length in Heating Mode Curve Name or the Piping Correction Factor for Height in Heating Mode Coefficient {1/m} inputs are used. Because these are blank changing the Equivalent Piping Length used for Piping Correction Factor in Cooling Mode {m}and Vertical Height used for Piping Correction Factor {m} only effects the cooling energy use of the system and has no effect on the heating use of the system. Does anyone know if these were intentionally left blank in the documentation and example files? Does anyone have a example curve and coefficient for the heating piping correction factor curve and coefficient?

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These were intentionally left blank (by me). You would have to look in the engineering specifications for the VRF unit in question. The change in heating capacity for a change in piping height or length is probably negligible and therefore there is no need to account for this and this input can be left blank (or you could enter 1 as is defaulted). You can look at Figure 12 in this document to see an example for the change in cooling performance with different pipe length and height. Notice the near vertical lines as piping length increases (sorry for the blurry picture). The fractional change in cooling performance is 1.0 at 25 m (e.g., actual Qcool = Qcap/1.0). This fraction decreases as piping length increases (to about 0.8 at ~435 m). The heating piping loss charts that I have seen do not have these vertical lines, meaning there is no change in heating capacity with changing pipe length/height.

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Thank you for the response, I figured it was intentional but I wanted to make sure!

( 2019-07-19 10:55:35 -0600 )edit