How to set Heating Design Temperature

asked 2024-01-30 15:47:41 -0500

JohnOnt
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updated 2024-01-31 09:33:48 -0500

13830 ●76 ●24 http://bigladdersoftware.com/

I am running a set of simulations using buildstock-batch, and would like to 'fix' the heating design temperature at 5°F to be the same for all the models.

It is to my understanding that the default method with the supplied weather data calculates the 99% bulb temperature threshold and sizes the HVAC system accordingly. I am able to see the calculated design temperature in the "in.xml" file for each model, but do not see how I can set it in the workflow_generator YML specification file?

In the Openstudio-HPXML documentation I can see the parameter here. But I do not know how to alter it.

Your help is very much appreciated!

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answered 2024-01-31 09:34:23 -0500

shorowit

10956 ●181 ●9 https://www.nrel.gov/b...

The general answer is that those OpenStudio-HPXML inputs are not currently exposed to ResStock. In order for an OpenStudio-HPXML input to be exposed, it needs to be added as an argument to the BuildResidentialHPXML measure, which is the OpenStudio measure ResStock uses to create the HPXML file for simulation.

However, in this particular case, there is another way to set the heating/cooling design temperatures. As the OpenStudio-HPXML documentation explains:

If HeatingDesignTemperature not provided, the 99% heating design temperature is obtained from the DESIGN CONDITIONS header section inside the EPW weather file. If not available in the EPW header, it is calculated from the 8760 hourly temperatures in the EPW."

So you can modify the DESIGN CONDITIONS header section of the EPW weather file to set the heating design temperature. And you can look at in.xml to verify it is being used.

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answered 2024-02-07 14:41:17 -0500

JohnOnt
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For a reference on how the header should be edited, the EPW weather file format is here.

The values that follow "Heating,1,..." in the second line of the file for Design Conditions are best understood from the .stat file that accompanies the EnergyPlus Weather Converter epw files:

Design Stat ColdestMonth    DB996   DB990   DP996   HR_DP996    DB_DP996    DP990   HR_DP990    DB_DP990    
Units   {}  {∞C}    {∞C}    {∞C}    {}  {∞C}    {∞C}    {}  {∞C}    {m/s}   {∞C}    {m/s}   {∞C}    {m/s}   {deg}   
Heating 1   -4.6    -2.6    -12.6   1.3 -0.5    -9.7    1.7 1.9 9.9 10.8    8.9 8.4 2.6 310

DB = Dry Bulb, DP = Dew Point, HR = Relative Humidity, and the subsequent numbers refer to the percentiles.

I ended up changing the second value in Coldest Month to -15°C to set the design temp to 5°F.

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