[Equest-users] Baseline Fan power calculation

[Nick Caton]

Hi Robert!

Bill is quite correct (although I was not watching my inbox so closely!) - BHP is being determined in the 7group spreadsheet referencing the Fan efficiency table prescribed in 90.1.  I am not an expert at de-constructing others' excel files, but observing the entries under the "fan motor efficiency" column, it's clear they're referencing an array which returns differing efficiencies, in turn dependent upon the calculated bhp.  I follow a similar procedure in my personal spreadsheet, but I haven't figured out how they hid the efficiency array =).

~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: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Monday, March 25, 2013 10:01 AM
To: RobertWichert; Nick Caton; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Baseline Fan power calculation

Robert,

I'm sure Nick is typing furiously as I write this, but I'll probably finish before him.

Taking a quick look at the spreadsheet that Nick attached to his email, it calculates baseline fan power using the method described in Appendix G and 6.5.3.1.1. Fan efficiency is included in the Pfan calculation per G3.1.2.9.
Fan efficiency is from ASHRAE 90.1, Table 10.8 as described in G3.1.2.9.

Regards,
Bill

William Bishop, PE, BEMP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
wbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>           www.pathfinder-ea.com<http://www.pathfinder-ea.com/>
P   Sustainability - the forest AND the trees. P

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of RobertWichert
Sent: Monday, March 25, 2013 10:52 AM
To: Nick Caton; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Baseline Fan power calculation

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.      Pfan 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 CFMS and CFMD carefully at the cited Table.  A CFM quantity representing the airflow each element encounters (CFMD) 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> [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<mailto: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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