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

[Bishop, Bill]

Hi Nitin,
You have to set the MIN-FLOW-RATIO to something less than 1 in order for the system to run at lower flowrate to get VFD fan energy savings. The MIN-FLOW-RATIO default is 1 and does not automatically change with selection of FAN-CONTROL. (However, the default for FAN-CONTROL changes to variable speed if the MIN-FLOW-RATIO is less than 1.)
Regards,
~Bill

From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Anil Jangid via Equest-users
Sent: Sunday, October 18, 2020 12:36 PM
To: Nitin Harjai <nitin.harjai28 at gmail.com>
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Difference between fan energy consumption almost same using constant speed and variable speed fan control

Dear Nitin,

You can change the system type like VAV system and it will give you savings of VFD speed. In eQuest single zone reheat with vfd option is allow to take vfd speed savings.

Thanks
Anil
——-

On Sun, 18 Oct 2020 at 9:52 PM, Nitin Harjai via Equest-users <equest-users at lists.onebuilding.org<mailto: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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