[Equest-users] Supply Fan Power
Paul Riemer
Paul.Riemer at dunhameng.com
Fri May 20 07:15:52 PDT 2011
Michael,
I see two paths:
1) Your exhaust fans are separate from your HVAC and they become process equipment. Thus they should be modeled identically between the models with possibly an exceptional calculation method for your fan motor efficiency improvement.
2) Your exhaust fans are part of your HVAC system. They now get a prorated portion of the baseline fan power. Here I think the reviewer expects your total system fan power was different between your models so your exhaust fan power should be different too.
I generally chose 1 for my toilet exhaust since its sizing is independent of any load calculation and can be operated independently of other system. More complicated systems have ended up as 2. I have not bought my 90.1-2007 User's Manual yet. Are there any examples in there? If not, we should craft some. Then what is the best way to get it endorsed or approved by ASHRAE?
Paul Riemer, PE, LEED AP
DUNHAM
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 8:51 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
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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:image002.jpg at 01CC16CC.9312E410]
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> [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<mailto: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<mailto:mshields at fstrategies.com>
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