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OS:AirLoopHVAC:UnitaryHeatPump:AirToAir not in my hvac_library.osm

asked 2017-06-23 11:48:49 -0500

pajordan gravatar image

updated 2017-06-26 06:51:25 -0500

I'm using OS 2.1.0 and viewing the Small Office DOE prototype (from here); in this prototype each zone is served by a unitary HP (OS:AirLoopHVAC:UnitaryHeatPump:AirToAir), but I can't find this object in my HVAC library. How can I get it to appear in my library to be able to add it to other models?

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answered 2017-06-26 06:29:49 -0500

From a quick look at the Small Office DOE prototype, seems it used an AirLoopHVAC:UnitaryHeatPump:AirToAir with a Single Speed DX Cooling Coil, a Single Speed DX Heating Coil, and a gas supplemental heating coil.

In the OS Library, you won't find this exactly, the closest you have is one where the supplemental heating is electric, called "Unitary - DX Heat Pump - Cycling - Elec Reheat".

image description

Couple of things to note:

  • I would advise against using an Unitary System for this unless you specifically need to, you'd be shooting yourself in the foot in my own humble opinion: it's much more complicated to work with. You can model a PSZ using a regular air loop. You can click to create a new system, and select "Packaged Rooftop Heat Pump" in OS App, then just change the supplemental electric heating coil with a Coil Gas instead:

PSZ using a regular air loop

  • If you really want to create one with a gas coil for supplemental heat, you'll need to write a script or measure for this, or better yet, you could also just use the Create DOE Prototype Building measure on BCL (developped as part of openstudio-standards) to generate the SmallOffice Prototype in an OpenStudio Model directly. Here's one of the PSZ loops for the SmallOffice prototype generated using the BCL measure.

image description

You can then clone that into your specific model using the command line or a measure. Note that there no point trying to clone it into your own hvac_library.osm currently as it would be there but you won't be able to select it in the OS App, that would require adding a new line to the source code (here)

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You could also just leverage the openstudio-standards gem in a script to create the PSZ-ACs directly in your model, something I could help with.

Julien Marrec gravatar image Julien Marrec  ( 2017-06-26 15:36:02 -0500 )edit

Thanks for the response, Julien.

I've tried creating two separate Small Office models - one having the "Unitary - DX Heat Pump - Cycling - Elec Reheat" systems and the other having the "Packaged Rooftop Heat Pump"-style systems (with the separated components for coils and fans).

I noticed that my fan energy consumption for the "Packaged Rooftop Heat Pump"-style system model is nearly twice that of the unitary model. As far as I know I have the inputs matching between the two (for efficiencies, sizing, and availability schedules). Any ideas as to why the fan energy would be so different?

pajordan gravatar image pajordan  ( 2017-06-26 17:21:48 -0500 )edit

The Unitary model uses a Fan:OnOff that is cycling. First, double check what you have entered for your regular air loop option: your fan parameters, as well as the hvac operation schedule (basically ensure it's always in a NightCycle mode, and adjust the night cycle offset (defaults to 1°C, should be zero...). I think you need the command line to do that though. Second, it might be related to my question here

Julien Marrec gravatar image Julien Marrec  ( 2017-06-27 02:38:08 -0500 )edit

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Asked: 2017-06-23 11:48:49 -0500

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Last updated: Jun 26 '17