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Two different IDFs producing exact same results

asked 2020-12-14 10:20:53 -0500

WJGSON gravatar image

updated 2020-12-17 11:28:10 -0500

I modified an idf file (single family residential prototype) to create a baseline and proposed case. I just changed out the HVAC system so one model has a gas furnace, the other a ducted heat pump,I left everything else the same.

models both run fine with minimal warnings and no errors. however, all CSV results produced are exactly the same. The difference in the idf files (and the sameness of the CSVs) has been verified through direct text comparison.

Using EnergyPlus 8.9.0

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I've now downloaded the files multiple times, ran them on different machines and different EPlus versions. Original residential prototypes are in version 8.6 which I cant download for windows (though I'm still pretty sure the problem is with me rather than the files) so running them as is is going to be hard.

WJGSON gravatar image WJGSON  ( 2020-12-14 15:30:12 -0500 )edit

For a bit more context. I took two residential IECC prototypes, both single family slab on grade buildings in the same climate zone meeting the same code cycle requirements. One had a gas furnace and one had a ducted heat pump system. I simply replaced all gas furnace related idf content with the heat pump related idf content. This was expected to represent an heat pump retrofit. I ran the models, then used the .mdd to drop some building level hourly meter objects into the baseline and retrofit models. it is the resulting CSVs that are the same for the baseline and proposed simulations.

WJGSON gravatar image WJGSON  ( 2020-12-15 10:18:37 -0500 )edit

The CSV files will output whatever information you request using Output:Variable. What Output:Variables have you requested in the idf files? If it's information about weather, or schedule values, or lighting, it's entirely possible that the output csv files will be equal even for different idf files.

kwalkerman gravatar image kwalkerman  ( 2020-12-17 05:10:35 -0500 )edit

Hi, thanks for the reply, I'm outputting the following:

Output:Meter,Electricity:Building ,Hourly; Output:Meter,Gas:Building ,Hourly

and, because i replaced a gas furnace with a heat pump, these should definitely be different. I've dug into a bit, the .eso files are the same except for the time simulated but the eio files show different system components. super weird...

WJGSON gravatar image WJGSON  ( 2020-12-17 10:28:21 -0500 )edit

Here is a link to the idf and epw files in question if anyone feels like having a look

WJGSON gravatar image WJGSON  ( 2020-12-17 10:38:20 -0500 )edit

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answered 2020-12-21 09:56:37 -0500

I took a look at the files you posted and found your source of confusion. You are currently reporting outputs for the "Electricity:Building" and "Gas:Building" meters, which indeed do not change between the two files. You probably want to be using the "Electricity:Facility" and "Gas:Facility" meters instead, as these meters include HVAC energy consumption. I switched to these meters in your IDF files and the results changed. If you open up the *.mtd file after running a simulation, you can see what outputs are included in these two meters.

For example, here are the outputs included in "Electricity:Building":

 For Meter=Electricity:Building [J], ResourceType=Electricity, Group=Building, contents are:
  LIVING HARDWIRED LIGHTING1:Lights Electric Energy
  LIVING PLUG-IN LIGHTING1:Lights Electric Energy
  DISHWASHER1:Electric Equipment Electric Energy
  REFRIGERATOR1:Electric Equipment Electric Energy
  CLOTHESWASHER1:Electric Equipment Electric Energy
  GAS_DRYER1:Electric Equipment Electric Energy
  GAS_RANGE1:Electric Equipment Electric Energy
  TELEVISION1:Electric Equipment Electric Energy
  GAS_MELS1:Electric Equipment Electric Energy
  IECC_ADJ1:Electric Equipment Electric Energy
  LIVING_UNIT1:Zone Ventilation Fan Electric Energy

and here are the outputs included in "Electricity:Facility":

 For Meter=Electricity:Facility [J], ResourceType=Electricity, contents are:
  LIVING HARDWIRED LIGHTING1:Lights Electric Energy
  LIVING PLUG-IN LIGHTING1:Lights Electric Energy
  DISHWASHER1:Electric Equipment Electric Energy
  REFRIGERATOR1:Electric Equipment Electric Energy
  CLOTHESWASHER1:Electric Equipment Electric Energy
  GAS_DRYER1:Electric Equipment Electric Energy
  GAS_RANGE1:Electric Equipment Electric Energy
  TELEVISION1:Electric Equipment Electric Energy
  GAS_MELS1:Electric Equipment Electric Energy
  IECC_ADJ1:Electric Equipment Electric Energy
  LIVING_UNIT1:Zone Ventilation Fan Electric Energy
  EXTERIOR-LIGHTS_UNIT1:Exterior Lights Electric Energy
  GARAGE-LIGHTS_UNIT1:Exterior Lights Electric Energy
  SUPPLY FAN_UNIT1:Fan Electric Energy
  MAIN FUEL HEATING COIL_UNIT1:Heating Coil Electric Energy
  DX COOLING COIL_UNIT1:Cooling Coil Electric Energy
  MAINS PRESSURE_UNIT1:Pump Electric Energy
  DX COOLING COIL_UNIT1:Cooling Coil Crankcase Heater Electric Energy

(Note the HVAC outputs above.)

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Asked: 2020-12-14 10:20:53 -0500

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Last updated: Dec 21 '20