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Zone equipment without VAV

asked 2020-02-12 00:04:33 -0500

tenna031's avatar

updated 2020-03-08 12:57:13 -0500

Hi everyone, I'm new to OS and Energyplus and I'm trying to set up a simple model with a central RTU and zone dampers (no VAV). My goal is to eventually run a BCVTB cosimulation that controls these zone dampers. In cases where there is no VAV and central air from the RTU is modulated only by zone dampers, does OpenStudio provide a standalone damper module that varies the mass flow rate according to setpoints? So far I have found AirTerminal:SingleDuct:Uncontrolled and AirTerminal:SingleDuct:VAV:NoReheat. Which one should I use? It makes sense that a zone damper can be modeled as a VAV equipment with no reheat coil, but I'm not sure how OS handles this case. Thanks!

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I'm not sure what you mean by zone dampers with no VAV? Later on you mention modeling a zone damper as a VAV equipment with no reheat coil, is that what you mean? In my mind, VAV, which stands for Variable Air Volume, would be the same thing as a zone damper at least from an energy modeling standpoint (I understand that they are different in real life). Whether the VAV has a reheat coil or not is a separate issue, but if you want to vary the mass flow rate according to setpoints than I would recommend using the AirTerminal:SingleDuct:VAV:NoReheat terminal.

anchapin's avatar anchapin  ( 2020-02-14 06:13:04 -0500 )edit

Thanks for your feedback. That's right, I wanted to verify that a zone damper can be modeled as a AirTerminal:SingleDuct:VAV:NoReheat. But if I'm changing its mass flow rate, does it matter if its an AirTerminal:SingleDuct:VAV:NoReheat or an AirTerminal:SingleDuct:ConstantVolume:NoReheat?

tenna031's avatar tenna031  ( 2020-02-14 13:22:22 -0500 )edit

I'm not sure, but I would think that even if you are using EMS & BCVTB that Energyplus/Openstudio won't let you change the mass flow rate of an AirTerminal:SingleDuct:ConstantVolume:NoReheat unless you are changing the design mass flow rate which in turn changes the current mass flow rate at each time step. @aaron-boranian might know the answer to this question.

anchapin's avatar anchapin  ( 2020-02-14 13:33:58 -0500 )edit

That's interesting. I was checking out the 9.2 I/O documentation at and found this in section 5.1.11:

tenna031's avatar tenna031  ( 2020-02-15 18:34:39 -0500 )edit

"An actuator called “AirTerminal:SingleDuct:ConstantVolume:NoReheat” is available with a control type called “Mass Flow Rate.” This actuator is available in models that use the single duct constant volume no reheat air terminal. The units are kg/s. This actuator is used to control the mass flow rate. Normally, the flow rate of single duct constant volume no reheat air terminals is fixed by the input, sizing results or OA requirement for DOA system, but this actuator provides a way to override the flow with Erl programs."

tenna031's avatar tenna031  ( 2020-02-15 18:34:49 -0500 )edit

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answered 2020-02-12 12:47:27 -0500

tenna031's avatar

It looks like AirTerminal:SingleDuct:Uncontrolled is now obsolete, and in the above case AirTerminal:SingleDuct:ConstantVolume:NoReheat is recommended for use.

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Asked: 2020-02-12 00:04:33 -0500

Seen: 184 times

Last updated: Feb 12 '20