[Equest-users] Difference between fan energy consumption almost same using constant speed and variable speed fan control

[John Aulbach]

 Hi Nitin:
If you set the system to single zone reheat, you have nothing to vary the airflow (VAV). So the fan tab should basically show the same fan kWh regardless of constant speed or variable speed. You need to have a system that will vary the airflow before you can set fan speed at variable.
Hope this helps.
John R Aulbach, PE
    On Sunday, October 18, 2020, 09:22:03 AM PDT, Nitin Harjai via Equest-users <equest-users at lists.onebuilding.org> wrote:  
 
 Hi all,
I am working on the project where the project space is served by chilled water to meet the building heat load. And in eQuest, I have considered the single zone Reheat system under the Air Side HVAC tab for AHU having 14200 CFM working 9 hours 6 days a week.
My doubt is that whether I set the fan controls constant speed or variable speed, the software generated fan energy consumption KWh are nearly the same (only a  difference of 16 KWh) between both the cases.
This seems that I will not get the benefit of variable speed fan control in case there is a VFD equipped to AHU.
Can anyone help me why there is a very little difference in fan energy consumption using constant speed and variable speed fan in the model. 

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