Multizone Packaged Rooftop Heat Pump for ASHRAE Baseline

asked 2016-07-07 16:48:55 -0600

Hello Modeling Community,

I have set up a small building model (<2300m2) with zones for each of the interior rooms. After setting up the geometry I wanted to configure a baseline following ASHRAE 90.1-2010, which recommends a Packaged Rooftop Heat Pump system. I set up a Packaged Rooftop Heat Pump system in OpenStudio, replacing the SingleZone setpoint manager with a Scheduled:DualSetpoint manager. After a lot of head scratching and model iterations I discovered that the EnergyPlus documentation for the HVACTemplate:System:UnitaryHeatPump:AirToAir states:

This system may serve one or more HVACTemplate:Zone:Unitary objects. If this system serves more than one zone, only one zone is specified as the control zone.

Which may explain why my system was not properly autosizing for the entire building.

So my questions are:

How do I setup a packaged rooftop heat pump system for a multizone building?
Can I use the packaged rooftop heat pump system as a preheater/precooler and at the zone level use heating and cooling diffusers? Does this still follow ASHRAE 90.1-2010?
Is it possible to autosize a packaged rooftop heat pump system for a building with multiple zones?
Are there alternative systems I could consider for a baseline?

Thank you for your time,

Justin

answered 2016-07-09 11:31:54 -0600

aparker

8177 ●4 ●18 http://www.openstudio.net/

This doesn't answer the questions you listed, but if you are trying to create a strict 90.1-2010 Appendix G baseline building, here's what I'd suggest:

It sounds like you have a nonresidential all-electric building that is less than 4 floors and less than 25,000ft2.
Per Table G3.1.1A your baseline HVAC system is "System 4-PSZ-HP" (packaged single zone heat pump)
Per G3.1.1: "For systems 1, 2, 3, and 4, each thermal block shall be modeled with its own HVAC system." So in this case you aren't creating a multizone system, you are creating a single zone system for each zone.
To model this in OpenStudio, add one of the Packaged Rooftop Heat Pump template systems for each zone.

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You can also try Andrew's AddSys4PSZHP measure.

MatthewSteen ( 2016-07-09 14:41:08 -0600 )edit

@aparker Thank you for the points of clarification, they helped me decided how to configure the systems for my model.

@MatthewSteen I first tried the Add a PSZ-HP to each zone component from the BCL but received the error user_script.rb in run: undefined method get for # (NoMethodError) for in.rb. Once I figured out how to load my own measures into my measure folder the AddSys4PSZHP measure from @aparker worked perfectly. Thank you!

JustinShultz ( 2016-07-11 15:06:51 -0600 )edit

Great! FYI @Julien Marrec.

MatthewSteen ( 2016-07-11 15:57:19 -0600 )edit

I wrote the Add PSZ HP to each zone measure on BCL. Would you mind getting me the full error stack trace you're getting? you can email it (with your problematic model too) at julien dot marrec at gmail.com

Julien Marrec ( 2016-07-12 00:15:41 -0600 )edit

Ok it was a tiny typo on line 157, space_type at this point is an OpenStudio::WorkspaceObject, and I was doing space_type = space_type.get instead of space_type = space_type.to_SpaceType.get

I updated the measure on BCL here

Julien Marrec ( 2016-07-20 05:30:26 -0600 )edit

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Multizone Packaged Rooftop Heat Pump for ASHRAE Baseline

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