[Equest-users] Appendix G Fan Simulation

Jason Wendel jwendel at heatheng.com
Fri Dec 4 10:48:24 PST 2009

Ok, so here's the spreadsheet I set up to calculate the bhp with the pressure drop allowances

>From eQuest

>From Table Fan Power Limitation Pressure Drop Adjustment

>From Table Fan Power Limitation

System #

Calculated CFM

Ducted Return (0.5)

Particulate Filtration Credit: MERV 13 thru 15 (0.9)

Sound Attenuation Section (0.15)

"A"      (Table

Allowable Fan System BHP (Table G3.1.2.9 also)

Allowable Nameplate Motor hp (Table


Packaged VAV System with HW Reheat








Packaged Multizone with HW reheat









Unit Heaters






Split System Single Zone DX with Electric Heat







.  From what you're saying, do I not even bother with the bhp input in the wizard mode, just set up the system and run the simulation, then calculate the kW/cfm and put that in from the detailed mode?  Do I use the total fan KW from the SV-A output and the cfm from that output (shown below)?
[cid:image002.png at 01CA74D8.49B16180]

From: Amanda Bogner [mailto:amanda at bvm-engineering.com]
Sent: Friday, December 04, 2009 11:40 AM
To: Jason Wendel
Subject: RE: [Equest-users] Appendix G Fan Simulation

You've indicated that you're using the BHP directly in eQuest.  But, I think you need to take this value and use the equations in G3.1.2.9 which will account for the fan motor efficiency.  It doesn't appear from the information below that you're doing this step.

>From here, you'll end up with a fan power wattage.  I usually divide this by the total supply air and input it in the detailed mode as a kW/CFM value.

If you would like to send me your detailed calculations, I can have a more thorough look at it.  Specifically:

-          what pressure drop allowances are you able to take

-          what are you calculating your 'A' value to be

-          can the pressure drop allowance be applied to 100% of the air

Amanda Bogner, PE LEED AP
Manager of Simulations
[cid:image001.png at 01CA74D7.AFBD7460]
BVM Engineering, Inc.
834 Inman Village Parkway
Suite 230
Atlanta, Georgia 30307
404.806.2018 x 103
404.806.2019 FAX

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jason Wendel
Sent: Friday, December 04, 2009 11:19 AM
To: 'Equest-users at lists.onebuilding.org'
Subject: Re: [Equest-users] Appendix G Fan Simulation

Sorry to rehash this but I've been going through the baseline fan power, and still don't have the answers I need.

I've got a 113,000 cfm (from the SV-A System Design Parameters report) VAVR system on my baseline that when I go through all the calculations for ASHRAE 90.1-2007 (from Table G3.1.2.9, Table and b) I get 176.13 bhp.   I put that in the wizard entry for BHP for the VAVR system and don't get any errors, BUT when I put in the bhp that I solved for the packaged multi-zone AHU's that will be used in the building also (92,000 cfm, 153.88 bhp), using the same calculations, it gives me an error that the static is at 56 in w.c., and it needs to be below 15.

What's going on?  Also, if you use the equations from Table and b, then the break horsepower is higher than the allowable nameplate hp.  Isn't that backwards?


From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Erickson
Sent: Sunday, September 20, 2009 10:39 AM
To: ron lamarre; Matthew Higgins
Cc: Equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Appendix G Fan Simulation

Ron, to comment on your statement, "I believe that the kW/CFM is based on the Baseline BHP and Baseline Fan Power formula in ASHRAE 90.1-2004 G3.2.1.9.  The CFM is the total building CFM", 90.1-2007 makes it the most clear that the CFM is actually ONLY the Baseline's peak SUPPLY CFM.  The same is true for 90.1-2004, it's just not very clear.  However the reviewers do know that this is true and have most recently been asking for a demonstration of calculation methodology.


Paul Erickson LEED AP
Affiliated Engineers, Inc. <http://www.aeieng.com/>
5802 Research Park Blvd. | Madison, WI  53719 | P 608.236.1112 | F 608.238.2614
perickson at aeieng.com<mailto:perickson at aeieng.com> | www.aeieng.com
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of ron lamarre
Sent: Friday, September 18, 2009 11:49 PM
To: Matthew Higgins
Cc: Equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Appendix G Fan Simulation

Hi to all:

I believe that the kW/CFM is based on the Baseline BHP and Baseline Fan Power formula in ASHRAE 90.1-2004 G3.2.1.9.  The CFM is the total building CFM; see the air-side summary report for the total bulding CFM.

To get the correct total building CFM, set the Baseline supply-air-to-room-air at a 20-degree F differential.  For instance, if your summer (cooling) set-point temp = 75 degreesF, then the cooling supply air temp from the unit is 55-degree F.  If your winter (heating) set-point temp is 70-degree F, then your heating supply air temp from the unit is 90-degree F.  Run a simulation and eQUEST will determine the CFM for each system based on this differential; then balance the systems to be under the 300 unmet hours limit.  Then open the air-side summary report to see the total CFM of all your systems.  Use that total CFM in the BHP and Baseline Fan Power calculations under G3.2.1.9.  To use the formulas, you need to use a calculator with a "natural log" button and an "e" button for the energy constant (e=1.28....just like "pie" = 3.14).
For a Baseline Type 3 PSZ System, the fan power should be in the neighborhood of 0.0007; this may be why GBCI questioned your result.  Then assign this fan power to each baseline PSZ system in your building and re-run the simulation.  Include the formula in the LEED submittal template or narrative to demonstrate how its calculated; as well as including the Air-side Summary Report.  GBCI will see both the total baseline CFM and the baseline fan power calculations.

The Proposed conditions are the proposed set-points, proposed supply air temps, and proposed kW/CFM for each system as designed.  If the RTU fans run continuously during occupancy periods, separate the supply air fan power, which is the kW to use, from the RTU power.  This allows design teams to take credit for using high efficient HVAC systems (low kW/CFM).

Hope this helps.

Ron Lamarre, AIA, NCARB
Architect - LEED AP

From: Matthew Higgins <higgins at edi-arch.com>
To: "Equest-users at lists.onebuilding.org" <Equest-users at lists.onebuilding.org>; BLDG SIM <bldg-sim at gard.com>
Sent: Thursday, September 17, 2009 5:12:10 PM
Subject: [Equest-users] Appendix G Fan Simulation

I've seen multiple posts regarding 2004 Appendix G Fan Power and one post from Ming Zeng suggested the following:
"Baseline model fan usually gives 0.00078KW/cfm.  For proposed fans, typically it is 0.00016-0.00018 KW/cfm/in static*"*

I have two problems related to this because my Baseline KW/cfm is closer to 0.001 KW/cfm for a bunch of unitary Type-3 systems, which is indefinitely way too high.

Many people have referred to the calculated fan power as an allowance, which to me, would appear to be a threshold not to exceed based on the 20deg-F delta for Appendix G Fan Sizing. I figure this is not the case because others refer to the fan power as something that is simulated in the model as a KW/cfm.
I've also seen posts where numbers are expressed as KW/kcfm, which would indicate fan power KW per thousand cfm; which again is not an applicable figure for simulation using eQuest.

I'm struggling with these items because a recent GBCI reviewer has asked me to re-calculate my fan power because my BHPs are a bit higher than they should be. When I "re-calculate" these values I do not come up with the numbers they do (BHP ASHRAE - attached).

I'm trying to reconcile my response and eQuest inputs before we re-submit, but I'm not sure what to do.

Much thanks.

-- Matthew Higgins, LEED AP + ASHRAE-HBDP
Environmental Dynamics, Inc.
Architecture and Sustainability Consulting Services
505.242.2851 x.103

Any data provided by the Consultant, verbal or written, are to be considered opinions of building energy and/or daylight performance. The Client understands that the Consultant has no control of occupant habits, equipment or material performance or characteristics, site or climate conditions or the Contractor's method of assembly, and that the Consultant's opinions regarding building energy/daylight performance are made on the basis of the Consultant's professional judgment and experience. The Consultant makes no warranty, express or implied, that the energy/daylight performance of the building will not vary from the Consultant's opinion of building energy/daylight performance.

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