[Equest-users] Baseline Fan power calculation

[RobertWichert]

I believe I have written about this in the past, but since this seems to 
be on-topic, I'll bring it up again.

The theoretical fan power equation, Fan BHP = (cfm x static press "w.c.) 
/ (6356 x fan efficiency) can be used to calculate the theoretical fan 
BHP, but you need the fan efficiency.  This seems to be NOT the way the 
BHP is being calculated by the spreadsheet that was attached previously.

Is there a reason for that?

Was there an assumed fan efficiency used in the spreadsheet, and was it 
based on anything particular, or just a conservative assumption?


Thanks!



Robert Wichert P.Eng. LEED AP BD&C
+1 916 966 9060
FAX +1 916 966 9068







===============================================

On 3/25/2013 7:34 AM, Nick Caton wrote:
>
> Hi Vamshi,
>
> I advise carefully reviewing the footnotes under Table 6.5.3.1.1A, 
> which include procedure for determining baseline fan power adjustments.
>
> 1.P_fan represents the sum power of all fans in a given baseline 
> system (with exception to baseline systems #6/#8, fan powered VAV boxes).
>
> 2.Again, there is not a separate supply/return power calculation (see 
> answer #1).  You can however account for adjustments present in 
> separate airstreams from the proposed design.
>
> 3.Probably not.  Review the difference between CFM_S and CFM_D 
> carefully at the cited Table.  A CFM quantity representing the airflow 
> each element encounters (CFM_D ) should be applied against each 
> pressure drop adjustment, not an 'aggregate' of supply+return.
>
> You may also find the attached resource published by 7group helpful to 
> cement your procedural understanding of how to arrive at the sum total 
> for "A."
>
> Regards,
>
> ~Nick
>
> cid:489575314 at 22072009-0ABB**
>
> **
>
> *NICK CATON, P.E.*
>
> SENIOR ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway, suite 200
>
> 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 
> *vamshi ranga
> *Sent:* Monday, March 25, 2013 8:17 AM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Baseline Fan power calculation
>
> Hi All,
>
> I have a doubt regarding calculating fan power as per ASHRAE 90.1-2007.
>
> My proposed system has, supply return and exhaust fans separately with 
> kW and cfm mentioned for each fan.
>
> So, for calculating baseline fan power,
>
> 1. should I calculate it separately for each fan type?
>
> 2. can I take pressure drop adjustment both in supply and return fan 
> power calculation?
>
> 3. should I sum all the cfms of supply, return and exhaust and than 
> apply pressure drop adjustments to aggregated cfm.
>
> Kindly help me out in solving the doubt. If you have any example fan 
> power calculations, or web links those could guide me regarding this, 
> plz do share them.
>
> Thanks in advance.
>
> Regards,
>
> Vamshi.
>
>
>
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