[Equest-users] Supply Fan Power

[Nick Caton]

Color me concerned... This reviewer may have an argument but I can't
reason it.  I think he/she may be leading us off the path regarding what
the baseline fan power calculations apply to...

 

You've got exhaust fans in a proposed model matching the construction
documents.  Sounds okay so far...  Going through this line by line:

 

*         I would start with directing the reviewer to the glossary.
The entry for "HVAC system" reads: the equipment, distribution systems,
and terminals that provide, either collectively or individually, the
processes of heating, ventilation, or air conditioning to a building or
portion of a building."

o   Clearly, an exhaust fan providing ventilation to a building
independent of other systems is an HVAC system.  The reviewer's phrasing
of "..independent fan systems of the HVAC systems" is a
misinterpretation.

o   Building on the understanding that an independent exhaust system is
a complete HVAC system, Table G3.1.10.a is as far as you need to go for
support of following the construction documents.

*         I'd again reject the reviewers' choice of words:  Exhaust fans
are not "independent fans of the HVAC systems."

*         Sections G3.1.2.8 and G3.1.2.9 agreeably apply only to
baseline systems.  They have no bearing on the topic at hand (what goes
in the proposed model), unless your baseline fan capacities/efficiency
calcs didn't follow the instructions.

*         The request to document the independent fan systems' energies
separately is not new.  May as well do that after all's said and done.

 

That's my initial take.  Thoughts, anyone?

 

~Nick

 

 

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 Patrick
J. O'Leary, Jr.
Sent: Friday, May 20, 2011 8:35 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

it reads to me that your initial interpretation is what the reviewer is
asking for.  on the other hand the question is what is constituting an
"independent" exhaust fan here.  if the exhaust fan is part of the
balance of the supply/return/exhaust system it probably should be
modeled as such as it is not really different than having a return fan
installed in the ductwork somewhere and not in a unit itself.  per hte
90.1 user's manual (page g-28 in 2004), "System fan electrical power for
supply, return, exhaust and relief fans is calculated based on the
following formula.  The power from this formula includes supply, return,
relief, and exhaust fans ..."   if the exhaust fan is not part of the
designed system supply/return/exhaust then i would think your initial
interpretation of what the reviewer is asking is correct.  whichever
situation applies make sure the response documents the purpose of the
exhaust fans and how 90.1 applies (including section/user manual
references).

On 5/20/11 6:15 AM, M. Shields wrote: 

The exact comment is this:

 

"The fan power spreadsheet for the Baseline and Proposed models indicate
that the fan power of the exhaust fans have not been modeled identically
in each model. All independent fan systems of the HVAC systems in the
actual design must be modeled identically between the Proposed and
Baseline models at actual equipment capacities (fan volume and fan
power) as required by Table G3.1.10 in the Proposed building column,
since the fan design air flow rates and fan power per Sections G3.1.2.8
and G3.1.2.9, respectively, only applies to system types 1 through 8 in
Table G3.1.1A. If appealing this credit, revise the Proposed and
Baseline models so all independent fan systems of the HVAC systems are
modeled identically between the Proposed and Baseline models. In
addition, separate the energy consumption and peak demand energy for
independent fans in Table 1.8.1 and Table 1.8.2 of the template and
provide revised SV-A reports for each model reflecting the changes."

 

I initially interpreted this to be that for exhaust systems the bhp/kw
needs to be identical in both buildings and based on the specified
equipment from the mechanical designer, however, my supply fan energy
was Ok.  After reading the comment and Appendix G I am not unsure if I
also need to specify the fan power to be the same for both models, ie
use table G3.1.2.9 to calculate fan power for both instead of just the
baseline.

 

From: equest-users-bounces at lists.onebuilding.org [
mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Patrick
J. O'Leary, Jr.
Sent: Friday, May 20, 2011 8:57 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power

 

from your wording of "independent" it sounds like you may have an
application where you have a unit in the proposed building that is
required but not provided in the design?  or something similar.  is this
the case?  if a unit is required in the proposed per the requirement all
spaces be heated/cooled (per the definitions) they are required to be
the same as the units in the baseline building.  if this is not the case
if you post the exact comment it may shed some light on the subject.
otherwise i would argue the comment is in error - if all of your zones
are served by units in the proposed and you have matching units in the
baseline (regardless of system types) then your approach would be
correct.  

On 5/20/11 5:31 AM, M. Shields wrote: 

Good Morning All,

 

I recently received comments back from LEED and one of them was about my
fan power.  In the submission I calculated all of my fan power using
G3.1.2.9 for the baseline building, and I used the actual fan power in
the proposed building.  The reviewer has commented that all independent
fan systems have to be modeled identically in both the baseline and the
proposed building.  The supply fans use very high efficiency motors, and
as such are substantially more efficient than the calculation that
G3.1.2.9 provides.  Is there no way to take credit for using high
efficiency supply fans?

 

Thanks,

 

____________________________
Michael Shields

Email: mshields at fstrategies.com

 

 
 
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