Comparison between a building using Ductless Mini Splits and VRF system resulted in 63% less power consumption in HVAC electricity.

asked 2017-05-26 21:04:40 -0500

melanie's avatar

updated 2017-05-27 16:56:21 -0500


I'm simulating a building with an air conditioning area of 1,860.3 m2. The actual air conditioner system consists of 34 Ductless Mini Splits of different power, most of them with COP = 2.9 w / w and the total power of the evaporators is 1,299,985 BTU. I validated the result of the simulation with the split system with the monthly electricity consumption of the building and it was ok (1-5% of difference). So, I proposed to change these system for an VRF. I picked the following models of LG (using the building component library of NREL): ARNU - 288TE4 (COP = 3.34), 264DTE4 (COP = 3.37), 312BTE4 COP = 3.3), 144BTE4 (COP = 3.54) and 096BTE4 (COP = 4.03). The total capacity of the internal units is now 906,800 BTU. Finally, I would like to know if the result of 62.36% annual less power consumption is reasonable or if these are too much ?(maximum monthly consumption difference 66,62% and minimal monthly consumption difference 29,37%). The city has an Humid subtropical climate.

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first of all,i would check sizing total sizing cooling capacity of DX cooling coils (Ductless units) and VRF terminal (internal) DX cooling coil Only if they are similar, annual consumption would be the difference. between VRF and ductless

ngkhanh's avatar ngkhanh  ( 2017-05-27 11:50:26 -0500 )edit

yes, but the actual system (mini split) is Oversized, so my VRF is smallest 1,299,985 btu vs 906,800 btu.

melanie's avatar melanie  ( 2017-05-27 16:58:27 -0500 )edit

@melanie: You could check your schedule especially fan operation schedule as on_off operation for ductless unit.Also check cooling/heating rate output variable of all DX coil. Otherwise, you might check alternative the performance curves from any other VRF manufacturer by using VRF_curve. My previous work required reinput all performance curves for both. It would be best if you could sample check electrical consumption of several ductless units for validation of your estimated HVAC consumption/bill consumption.

ngkhanh's avatar ngkhanh  ( 2017-05-28 13:59:58 -0500 )edit