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Access to Cold Water Supply Temperature for WaterUse:Equipment in OpenStudio

asked 2016-07-19 17:18:32 -0500

updated 2017-05-08 16:10:57 -0500

I have setup a WaterUse:Equipment component in my OpenStudio model following this tutorial. However, I would like to edit the Cold Water Supply Temperature Schedule Name input to the WaterUse:Equipment.

I am familiar with how to do this in EnergyPlus as it is simply the input below the Hot Water Supply Temperature Schedule Name, can you help me set this input within OpenStudio?

I noticed the WaterHeater:Mixed component has a Cold Water Supply Temperature Schedule Name that provides input to the boiler but the WaterUse:Equipment is not doing the proper mixing because the supply temperature is set to the default 10C.

Thank you,


Edit 1 I noticed that the Cold Water Supply Temperature Schedule Name for the WaterHeater:Mixed component does not appear to have an effect on the energy consumption of the Water Heater when elevating hotter or colder supply water. Am I missing something?

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answered 2016-07-20 04:30:31 -0500

updated 2016-07-20 04:56:23 -0500

The object you should really modify in your case is the Site:WaterMainsTemperature, where you can use either a Schedule or a Correlation.

It isn't available in the application, but it's easy to access it in the API.

# Get the Site:MainsWaterTemperature
mains = model.getSiteWaterMainsTemperature

# Case 1: Calculation Method = Schedule
# temp_sch is an OpenStudio::Model::Schedule
calculation_method = "Schedule"

# Case 2: Calculation Method = Correlation
# avg_oa_temp, max_diff_monthly_oa_temp are doubles
calculation_method = "Correlation"

BCL Measure

I uploaded a measure I wrote to do just this on the BCL: Set Site WaterMains Temeprature. There is an Excel spreadsheet in the 'resources' folder that I created to calculate the Correlation coefficients from the weather .stat file.

Note that I often find the resulting temperatures to be a bit extreme... Not sure if my fault or the original methodology. I couldn't find any mistake but it doesn't mean I didn't make one, feel free to ping me if you notice one.

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Thank you for your response, I'm not sure how to access the API so I will likely use your measure. Do I need to drop in a PlantComponent:TemperatureSource to the water loop or does the Site:WaterMainsTemperature not need to be added to any loops?

JustinShultz's avatar JustinShultz  ( 2016-07-20 09:31:54 -0500 )edit

It isn't added to any loop no. Read the introduction paragraph in the I/O for Site:WaterMainsTemperature

"The mains temperatures are used as default, make-up water temperature inputs for several plant objects, including: WaterUse:Equipment, WaterUse:Connections, WaterHeater:Mixed and WaterHeater:Stratified. The mains temperatures are also used in the water systems objects to model the temperature of cold water supplies"

Julien Marrec's avatar Julien Marrec  ( 2016-07-20 09:44:10 -0500 )edit

I understand now. Thank you!

JustinShultz's avatar JustinShultz  ( 2016-07-20 10:00:42 -0500 )edit

The E+ I/O, and his companion the Engineering Reference, are your two best friends to navigate the complex world of E+ :)

Julien Marrec's avatar Julien Marrec  ( 2016-07-20 10:29:03 -0500 )edit

Agreed! I like to jump to LaTeX generated PDFs for EnergyPlus 8.5.0. Much cleaner and searchable.

JustinShultz's avatar JustinShultz  ( 2016-07-20 10:32:50 -0500 )edit

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Asked: 2016-07-19 17:18:32 -0500

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Last updated: Jul 20 '16