[Bldg-sim] Appendix G Fan Power

[Michael Tillou]

The Fan Power Allowance in ASHRAE 90.1 is based on "good" engineering
practice.  I have attached a .pdf showing the System Pressure Drops used in
determining the allowances for both the VAV fan system and the CV fan
system.  The fan efficiency assumed in both cases is 65% and air velocity is
assumed to be 400 fpm through the coils and filters.  Filter pressure drop
assumes dirty filters.  The standard allows additional credits for systems
with heat recovery, high performance filtration, lower design supply air
temperatures and the use of relief fans vs return fans.

Also, addendum ac of ASHRAE 90.1-2004 modified the fan power calculation
methodology allowing an expanded list of allowances that better suits a
wider range of building types including hospitals and lab buildings.  Those
changes are incorporated into Standard 90.1-2007.

I think that Michael Williamson gave the best reason yet why it is important
to split the baseline fan power among the supply, return and exhaust fan
components.  Like many others I distribute baseline fan hp using the same
ratios as the proposed design even though the baseline system configurations
may be slightly different.

Finally, three cheers to GBCI for putting review teams together that will
actually do a decent job of ensuring compliance with Standard 90.1 rather
than just taking the design teams word for it.  Maybe folks will begin to
realize that exceeding 90.1-2004 by 20-30% is actually a challenge and
building designs will begin to reflect the changes necessary to meet that
challenge.

Regards,

Mike

Michael Tillou, PE
Associate Vice President
Energy Services
Cannon Design



On Thu, Jul 2, 2009 at 12:51 PM, Zeng, Ming <mzeng at leoadaly.com> wrote:

>  Hi James,
>
> I actually feel the baseline model fan energy is too small.  Baseline model
> fan usually gives 0.00078KW/cfm.  For proposed fans, typically it is
> 0.00016-0.00018 KW/cfm/in static.  With cooling coil at 1 inch, mid life
> filter at 1.5 (30% and 85%), energy wheel at 0.8, external static of 1.8
> inch, you will get .00081 KW/CFM.  And the return fan and general exhaust
> fans haven’t been included yet.
>
>
>
> Do you typically have less pressure drop than listed for the system?  Shall
> we use the clean filter or midlife filter for pressure calc?
>
>
>
> *Ming Zeng*, PE, LEED® Accredited Professional
>
> Mechanical Engineer
>
>
>
> [image: LEO A DALY]
>
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> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *James Hess
> *Sent:* Thursday, July 02, 2009 10:43 AM
> *To:* Gregg Liddick; Bldg-Sim
>
> *Subject:* Re: [Bldg-sim] Appendix G Fan Power
>
>
>
> Gregg,
>
>
>
> I appreciate the response.
>
>
>
> I see what they are trying to do; I just don’t think it needs to be done.
> The total fan energy consumption (supply, return, exhaust) is the same for
> comparison purposes to the proposed design model.
>
>
>
> On many projects, the baseline system is different than the proposed àpackaged single zone systems versus packaged VAV RTU, for example.
> Therefore, there would not be any return fans on the packaged single zone
> systems to allocate fan energy to.  I don’t know if anyone is looking at
> this to that level of detail.  Another separate issue is that the Appendix G
> fan energy equation way over estimates the fan energy associated with real
> packaged single zone systems, but I’ve posted previously on that issue and
> won’t bore anyone with those details.
>
>
>
> I guess the bottom line is that if GBCI absolutely insists that the
> baseline fan energy be broken into components, we’ll come up with some kind
> of percentage allocation, similar to what you have done, as applied to the
> total baseline fan energy consumption for the sole purpose of filling out
> the template.
>
>
>
> Thanks! J
>
>
>
> Regards,
>
>
>
>
>
> JAH
>
> * *
>
> *James A.  Hess, PE, CEM*
>
> Energy Engineer
>
> TME, Inc.
>
> Little Rock, AR
>
> ph   501-666-6776
>
> cell  501-351-4667
>
> *jhess at tmecorp.com <email at tmecorp.com>*
>
>
>
> *From:* Gregg Liddick [mailto:gliddick at theepstengroup.com]
> *Sent:* Thursday, July 02, 2009 9:35 AM
> *To:* James Hess; Bldg-Sim
> *Subject:* RE: [Bldg-sim] Appendix G Fan Power
>
>
>
> Hi James,
>
>
>
> As far as I’m concerned the main point of having project teams break the
> fan energy down into components is to ensure that the baseline fan power
> derived from the fan supply volume using Table G3.1.2.9 is not all
> attributed to supply fans if exhaust fans, return fans, etc. exist.
>
>
>
> Regarding the breakdown, as far as I know you’re correct in that there is
> no guidance on that and what I do is take the percentages based on total fan
> power from the proposed case and apply it to the baseline case (e.g. 70%
> supply, 20% return, 10% exhaust).
>
>
>
>
>
> Best Regards,
>
>
>
> Gregg Liddick, EIT, LEED® AP
>
>
>
> The Epsten Group, Inc.
>
> 429 Edgewood Avenue
>
> Atlanta GA 30312
>
> Phone: 404-577-0370  ext. 102
>
> Fax: 404-577-1739
>
> www.theepstengroup.com
>
>
>
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> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *James Hess
> *Sent:* Thursday, July 02, 2009 10:28 AM
> *To:* Bldg-Sim
> *Subject:* Re: [Bldg-sim] Appendix G Fan Power
>
>
>
> We got a review comment on a recent LEED project asking us to break down
> the baseline HVAC power into components even though there is no direction,
> or requirement, from 90.1-2004 to do so.
>
>
>
> Can someone please help me understand why this would be necessary?
>
>
>
> LEED guidelines say we have to model per Appendix G, but Appendix G doesn't
> say we have to do this.
>
>
>
> I do not think it is necessary to do this as the baseline total fan energy
> consumption numbers would still be the same.
>
>
>
> The equation in Appendix G is meant to give a total allowance (for each
> system) for supply, return, and exhaust fans. It doesn't matter if we break
> the allowance down into components or not as the total fan energy
> consumption remains the same. Therefore, there is no value in doing this.
>
>
>
> If we did break the fan energy numbers into components, how would we do
> that given that there is no direction from ASHRAE or LEED on how to do this?
>
>
>
> Thoughts?
>
>
>
> Regards,
>
>
>
> James A. Hess, PE, CEM
>
> Energy Engineer
>
> TME, Inc.
>
>
> On Jul 2, 2009, at 8:41 AM, "Jeremy Poling" <jpoling at epsteinglobal.com>
> wrote:
>
>  This issue will start to become a problem for anyone running energy
> models for LEED projects – reviewers on the new review teams are asking to
> see the total fan power for the baseline broken into individual components
> and reported as such in the template for Energy and Atmosphere Credit 1.
> The 90.1-2004 User’s Manual is also silent on the issue; however it raises
> another issue.  In the example (Example G-J on page G-28) the calculations
> use total building supply CFM for an 80,000SF medical office building.
>  Since the baseline is System 5 in that example and there would be multiple
> zones for the baseline, it appears that the equation should be used for the
> whole building only and not individual systems.  Is this how you are
> applying the formulas?  The user’s manual notes that fan powered VAV boxes
> are NOT included in the total fan power number as calculated from G3.1.2.9.
>
>
>
> *Jeremy R. Poling, LEED AP*
> Senior Sustainability Analyst
> Strategic Services
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> Architecture
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>   ------------------------------
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Ellen Franconi
> *Sent:* Thursday, July 02, 2009 7:37 AM
> *To:* Vikram Sami; Bldg-Sim; Michael I Rosenberg
> *Subject:* Re: [Bldg-sim] Appendix G Fan Power
>
>
>
> At my firm, we proportion the baseline total fan power determined as an
> aggregated W/CFM based on  the hp assigned to the fan motors (supply,
> return, exhaust) in the design documents. Of course this assumes that your
> baseline and your proposed design have a one-to-one fan correspondence.
>
> Ellen
>
>
>
>
>
> Ellen Franconi, Ph.D., LEED AP
> Senior Energy Analyst
> Architectural Energy Corporation
> 2540 Frontier Avenue
> Boulder, CO 80301
> tel. 303-444-4149
> fax 303-444-4303
> efranconi at archenergy.com
> http://www.archenergy.com/
>
>
> >>> "Rosenberg, Michael I" <michael.rosenberg at pnl.gov> 7/1/2009 4:48 PM
> >>>
>
> You have calculated the kW/cfm correctly according to the 2004 version of
> Appendix G. The allowance actually goes up a little in 2007, for your case.
> As for the second part of your question, no you do not apply the same kW/cfm
> to the exhaust fan. The calculated allowed fan power the total allowed power
> for all fans that are part of the system, including the exhaust fan. The cfm
> component is based on the supply fan cfm only. Unfortunately, Appendix G
> gives no direction on how to divide the allowed fan power up among the
> various fans in the system.
>
>
>
> Mike
>
>
>
> *__________________________*
>
> *Michael Rosenberg*
> Senior Commercial Buildings Energy Analyst
> ENERGY & ENVIRONMENT DIRECTORATE
>
> Pacific Northwest National Laboratory
> 2032 Todd Street
> Eugene, OR 97405
> (541) 844-1960
> michael.rosenberg at pnl.gov
> www.pnl.gov
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Vikram Sami
> *Sent:* Wednesday, July 01, 2009 3:03 PM
> *To:* Bldg-Sim
> *Subject:* [Bldg-sim] Appendix G Fan Power
>
>
>
> G3.1.2.9 Gives you a formula for calculating system fan electrical power
> for supply, return, exhaust and relief. Lets sat I have a zone with a PSZ-HP
> that has a supply volume of 1500 cfm. Using this formula along with table
> G3.1.2.9 I get a fan horse power of 1.29 and kW of 1.17. This equates to
> 0.00078 kW/cfm – which seems really high.
>
>
>
> The second part to my question is assuming I have 500cfm of exhaust in this
> zone, do I apply the same kW/cfm to the exhaust fans as well as the return
> fans? It seems that the lower the fan volume the more inefficient the
> Appendix G values get from these tables.
>
>
>
> Any guidance would be much appreciated.
>
>
>
> *Vikram Sami,* LEED AP
> Direct Phone 404-253-1466 | Direct Fax 404-253-1366
>
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