[Equest-users] VAV minimum flow

[xiaoyang shi]

Hi Nick,

How do you think this standard from ASHRAE 90.1 G3.1.3.13 VAV Minimum Flow
Setpoints (Systems 5 and 7). Minimum volume setpoints for VAV reheat boxes
shall be 0.4 cfm/ft2 of floor area served or the minimum ventilation rate,
whichever is larger.

In my opinion, it means, if we set "Minimum Design Flow is 0.5 cfm/ft2", the
VAV minimum flow should be set 80% (we assume the minimum ventilation rate
is smaller than VAV minimum flow.), Or I am wrong?

Thank you very much.

Best,
Xiaoyang


On Fri, Mar 11, 2011 at 5:18 PM, Nick Caton <ncaton at smithboucher.com> wrote:

>  Hi there Xiaoyang,
>
>
>
> VAV min flows can be set both in wizards and in detailed edit modes.  See
> following screenshots.
>
>
>
> The “standard” depends on the HVAC design, and specifically how ventilation
> air is being distributed.  There’s a range of CFM’s that the factory will
> set as a minimum terminal unit at depending on the size, but it may well be
> zero if you are distributing ventilation air via DOAS in certain ways.  I’d
> suggest asking your HVAC designer directly what the minimum is for each unit
> (it’s probably scheduled), and use that info to either come up with an
> average for each zone or to set the minimum for each zone separately.
>
>
>
> Here’s the wizard…
>
> … and in detailed, double click on a space served by a VAV system, under
> the Airside HVAC tab, to find the following window.  In this case, the
> minimum flow is set to 30% (0.30):
>
>
>
>
>
> ~Nick
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> www.smithboucher.com* *
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *xiaoyang shi
> *Sent:* Friday, March 11, 2011 2:35 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] VAV minimum flow
>
>
>
> Hi folks,
>
> Do you know how to set the "VAV minimum flow" (percentage) at the "HVAC
> zones: temperatures and Air Flows" panel? eQUEST default number is 40%. Is
> there any standard?
>
> Thank you.
>
>
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