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# What VRF output variables should I consider to calculate electric energy consumption?

I'm working on a building with:

• 1 VRF System (Outdoor Unit);
• 3 VRF Terminals (Indoor Units)

At this moment, I generated the IDF by using OpenStudio SketchUp Plugin.

My aim is to know the total electric energy consumed by the whole HVAC system of the building during a certain period of time.

Reading the EnergyPlus docuentation, I've seen these two output variables:

1. VRF Heat Pump Cooling/Heating Electric Energy: it measures electricity consumption of the VRF heat pump (outdoor unit) for the time period being reported. It includes electricity used by the compressor and the condenser fan.

2. Zone VRF Air Terminal Cooling/Heating Electric Energy: it's the electricity consumption associated to a single zone terminal unit (indoor unit) for a certain time period. This value is calculated for each HVAC system timestep being simulated, and the results are summed for the time step being reported. There's this variable for each VRF Terminal Unit.

So, I thought that, to calculate the total electric energy consumption of the whole HVAC of the building, I could sum up the values of these variables (in this way, I sum up "Indoor Units" + "Outdoor Unit" consumptions).

What do you think, is it ok, or should I consider other output variables in order to calculate the total electric consumption?

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Have you considered looking at Output Meters instead of individual object Output Variables? For example, there is Output:Meter,Electricity:HVAC,hourly; !- [J] for all HVAC electricity energy use, or you could disaggregate by heating/cooling and use Output:Meter,Heating:Electricity,hourly; !- [J] and Output:Meter,Cooling:Electricity,hourly; !- [J] (you might also need another meter for fan energy). See the .mdd file after you run a simulation for all the output meters available to you.

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Hi shorowit! Thanks for your reply! I had never used "Output Meters" before; it seems to fit my need!

( 2020-09-11 11:42:01 -0500 )edit
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Also note that the .mtd file will tell you what Output Variables are included on an Output Meter for a given model.

( 2020-09-11 11:47:10 -0500 )edit

Thanks, perfect!

( 2020-09-11 11:49:39 -0500 )edit