How to model constant air volume system using eQUEST?

equest
cav

asked 2018-10-12 09:33:05 -0600

yongqingzhao

939 ●6 ●10

updated 2018-10-15 19:06:51 -0600

__AmirRoth__

4446 ●5 ●17 http://bleedinggreenna...

How do you model constant air volume system using eQEST? As I know,most of eQUEST users model constant volume system as VAV system but set the minimum airflow setpoint to 1.0.And I think this method is not appropriate,because the VAV system adjusts the cooling and heating load by varying the supply air volume but keep the supply air temperature constant, set the minimum airflow setpoint of VAV system to 1.0 means that the supply air volume and temperature are kept constant,however,the constant air volume system adjusts the heating and cooling load by varying the supply air temperature but keep the supply air volume contstant. I always model the constant air volume as single zone reheat.And I want to kown what your solution to this problem is!

Any suggestion?Thanks!

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answered 2018-10-15 17:53:22 -0600

Erik Kolderup
343 ●2 ●9

You can change the system input for "Cool Control" to have the supply air temperature vary. You probably want to choose "Warmest" as the option instead of "Constant". That will reset the supply air temperature each hour based on zone demand.

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answered 2018-10-15 22:44:20 -0600

Nick Caton
516 ●2 ●4

So to be clear, you have quite a few options with VAV and with CV system types in eQuest, and a VAV system made to produce CV can still be made to vary supply temperature if that's desired. If you're looking for something like a classification to help you guide which system type options to consider for a given project, I may suggest investing a little time reviewing & absorbing the reference manual entries at and beneat: Volume 1: Basics > Air-side Components > Introduction > Air Systems. There you can find a descriptive/illustrated classification of airside system types. It isn't comprehensive but could help you get the lay of the land.

I wouldn't venture that I really have a favorite per se, however for system types which are natively CV, I probably utilize PTAC, UHT/UVT, PSZ and MZS/PMZS system types most often. It is a little extra work to make a VAV system type behave as though it's contant volume, however that effort can make parametric "VAV conversion" a relatively simple task, and for that reason primarily I and others do often leverage VAVS/PVAVS some fraction of the time where I intend to quantify savings potential for such an ECM.

I hope that's helpful!