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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.

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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

Seen: 201 times

Last updated: Jun 26 '17