[Equest-users] Baseline Fan power calculation

[Cam Fitzgerald]

All,

 

It seems there is much confusion on this issue. The Proposed fans are all
modeled explicitly (with the fan power as designed). In the Baseline case
each HVAC system fan power (Section G3.1.2.9)  is calculated using the
supply airflow (Section G3.1.2.8) based on 20 F space to supply air
temperature difference. If the Proposed system uses multiple fans, then the
calculated system fan power is distributed among the fans in the Proposed
design. Appendix G does not provide any guidance for how this power should
be distributed among the system fans in the Baseline system, but usually
projects use the same proportion of the total system fan power as the
Proposed design. All the fan power can be modeled as a single supply fan,
but that will apply all the heat gain from the fan to the supply airstream
which may not be realistic for large systems. Note that exhaust fans in the
Proposed design that operate continuously during occupied periods are
considered part of the system and their power is included in the calculated
Baseline fan power. Exhaust fans that operate intermittently are considered
a process load and must be modeled identically in both cases. If the
Proposed process exhaust fan motor is larger than one HP, the motor
efficiency is regulated by  Section 10 and savings may be claimed for using
high efficiency motors as compared to the minimum efficiency from Table
10.8.

 

Hope this helps!

 

Cam Fitzgerald

 

Energy Opportunities/a 7group company

 

 

 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of vamshi
ranga
Sent: Tuesday, March 26, 2013 3:27 AM
To: Nick Caton
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Baseline Fan power calculation

 

Dear Nick Caton,

 

Thank you very much for valuable inputs, from this it is clear that, 

 

1. However there are different motors used in Proposed case for supply,
return and exhaust with different kW/cfm, we need to use one single motor in
with one kW/cfm in baseline case

2. In EAp2 Section 1 4 Tables of LEED under "Table 1.4.2", it asks for
separate wattage of supply, return and exhaust fans in baseline case, So,
there we need to enter as "Not Applicable"

 

Please let me know if my understanding is wrong.

 

Thanks,

Vamshi.

 

On Mon, Mar 25, 2013 at 8:04 PM, Nick Caton <ncaton at smithboucher.com> 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

 <http://www.smithboucher.com> 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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