[Equest-users] Supply Fan Power
Paul Diglio
paul.diglio at sbcglobal.net
Fri May 20 08:11:33 PDT 2011
The makeup air can come from operable windows or infiltration and does not
necessarily need to be conditioned.
Paul Diglio
________________________________
From: "Bishop, Bill" <wbishop at pathfinder-ea.com>
To: M. Shields <mshields at fstrategies.com>; Paul Diglio
<paul.diglio at sbcglobal.net>; equest-users at lists.onebuilding.org
Sent: Fri, May 20, 2011 11:03:05 AM
Subject: RE: [Equest-users] Supply Fan Power
Maybe this is the source of the confusion. I disagree that toilet exhaust fans
constitute independent HVAC systems that have to modeled separately in the
baseline. To me, toilet exhaust, kitchen exhaust and clothes dryer exhaust are
all components of the system that heats, cools and ventilates the zone(s). The
air handlers, heating and cooling coils that serve these zones are designed to
supply and condition the ventilation air that is exhausted, regardless of
whether or not the exhaust is at the air handler or through a zonal exhaust fan.
Yes, a toilet exhaust fan can operate with the HVAC system off, but the makeup
air has to come from somewhere, and it needs to be heated/cooled (even if
indirectly by mixing with the room air). I mentioned previously that I usually
omit exhaust fans in baseline systems. Another reason I do this is because
eQUEST zonal exhaust fans cannot operate when the system fan is off.
My personal interpretation of G3.2.1.9 is that if you choose to model separate
supply and exhaust fans in the baseline system, the calculated baseline fan
power is split up into supply and exhaust components so that their total power
equals the calculated value. I do not think G3.2.1.9 requires you to model
separate fans for any reason. It only adds complexity and modeling effort, not
baseline fan energy.
Regards,
Bill
From:equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of M. Shields
Sent: Friday, May 20, 2011 10:48 AM
To: 'Paul Diglio'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power
I agree the toilet exhaust system would be independent, but I guess I am having
trouble coming up with an example of an exhaust system which is not independent
other than an ERV which seems to be covered under G3.1.2.10. Thus if everything
other than ERVs are independent, why does G3.1.2.9 specify exhaust as one of the
systems to be included in that calculation?
From:Paul Diglio [mailto:paul.diglio at sbcglobal.net]
Sent: Friday, May 20, 2011 10:37 AM
To: M. Shields; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Supply Fan Power
Michael:
Would not the toilet exhaust be an independent system? It does not return air
to the HVAC system and can operate with the HVAC system off.
I am modeling a residential high rise and am modeling the kitchen exhaust hoods
as an independent system. In my case the toilet exhaust fans have been
eliminated and the toilet/apartment exhaust air is returned to an ERV. Each
apartment is being supplied with ventilation air from a DOAS. In my case, I
will model the toilet exhaust as part of the HVAC system.
Paul Diglio
________________________________
From:M. Shields <mshields at fstrategies.com>
To: equest-users at lists.onebuilding.org
Sent: Fri, May 20, 2011 10:25:43 AM
Subject: Re: [Equest-users] Supply Fan Power
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
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
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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