[Equest-users] Supply Fan Power
M. Shields
mshields at fstrategies.com
Fri May 20 07:25:43 PDT 2011
Thanks for all of the comments. I think I may have figured out how the
reviewer got confused.
As part of my documentation I provided a table which showed the supply and
exhaust cfm, bhp, and kw as calculated from G3.2.1.9 for the baseline
building. I then showed the same for the proposed building using the actual
equipment specified. The building has stacks of apartment units, each stack
has an exhaust riser which has a continuously running fan on the roof. I am
interpreting everything correctly now, the baseline building should only
list the supply cfm, bhp, and kw as calculated from G3.2.1.9 which includes
the fan power from this exhaust riser. The proposed building would then use
the actual supply fan and exhaust fans specified.
Does this seem like the correct path? Alternatively the exhaust riser could
be modeled separately in both buildings using the proposed equipment as a
process load.
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Friday, May 20, 2011 9:51 AM
To: Nick Caton; Patrick J. O'Leary, Jr.; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power
Michael,
I'm confused by your LEED reviewer's comments. As Patrick mentioned, it
would help to know what the reviewer means by "independent fan systems". I
can think of only two situations where you would need to model identical fan
power in the baseline and proposed models. One is if you have no heating
and/or cooling system in the proposed design, in which case the proposed
system "shall be identical to the system modeled in the baseline building
design" per Table G3.1(10.). Since you mention that you used the actual fan
power in the proposed building, I'm assuming that heating and cooling
systems have been specified for your proposed design.
The other situation is for process loads. If you have fan power associated
with non-HVAC systems, it should be treated as a process load and modeled
identically between the baseline and proposed designs. An example of this
that has been discussed on this forum previously is parking garage exhaust.
I rarely model anything but supply fans in the baseline model unless there
are process loads. I see no point in modeling return, exhaust or relief
fans. The fan power calculated in G3.1.2.9 is for the sum of supply, return,
exhaust and relief fans. The baseline systems have to move the same amount
of air regardless of the combination of fan types, and the fan power is
based on, and entered as, kW/cfm, so you will end up with the same fan
energy in the baseline model regardless of how many fans you model for each
baseline system.
I don't know what the reviewer is trying to say with their comment about
system types 1 through 8 and Table G3.1.1A.
Regards,
Bill
Signature in jpg form
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Friday, May 20, 2011 9:50 AM
To: Patrick J. O'Leary, Jr.; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power
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
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 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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