[Bldg-sim] Fan power calculation for proposed model - Venn diagram

Thu Sep 3 19:07:59 PDT 2015

Bill,

I think you've exceeded the normal allotment of wit allowed for a single BLDG-SIM post :-)

I really like the Venn Diagram you've posted, because it helped to clarify for me the 
differences between Dweebs, Geeks, Dorks, and Nerds.  Now I will know whether I'm being 
insulted or complimented.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

On 9/2/2015 3:26 PM, Bishop, Bill wrote:
> Nick,
>
> Love your posts! Guess you can call me a "fan".
>
> Here's a Venn diagram in your honor:
>
> [http://gaspull.geeksaresexytech.netdna-cdn.com/wp-content/uploads/2009/09/nerd-venn-diagram.jpg]
>
> ~Bill
>
> ________________________________
> From: Bldg-sim [bldg-sim-bounces at lists.onebuilding.org] on behalf of Nicholas Caton [ncaton at catonenergy.com]
> Sent: Wednesday, September 02, 2015 6:11 PM
> To: Duggin, Cory; Nicholas Blanton; Jim Dirkes
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] Fan power calculation for proposed model
>
> The Venn diagram of individuals who are well enough versed in both energy simulation AND the nuances of actual fan power consumption AND sufficiently motivated to misrepresent energy consumption with their hard work is I think relatively small.  As such, the potential for deliberately skewing performance by doctoring up part load curves doesn’t come up often for discussion!  It’s certainly a possibility, however…
>
> To respond to the other Nick’s query: 90.1 Appendix G (and by its relatively wide incorporation through LEED) does mandate part load fan curves for baseline systems with VAV.  I haven’t (honestly!) tried such sneaky tactics before with LEED submissions, but based on recent review commentary (in the past year) I would be surprised if an over-inflated fan power consumption managed to slip through the cracks. GBCI’s reviewers have proven eager to check “full load equivalent” operation against annual consumption, sometimes on more things than are usually appropriate – fans included.
>
> Rounding back to the original query – I think another perspective is that it’s always ‘safe’ to reference design documentation when you have no better information.  If you are trying to evaluate relative savings with existing systems, what’s measured/observed in the field or in “as-built” documentation should generally trump what’s on the original plans.  Based on the ultimate function/purpose of your simulation (informing actual design decisions vs. quickly assembling a LEED-compliant submission), you can make the call as to whether gathering the extra info from the field is entirely necessary/appropriate.
>
> If you’re looking to source fan curves “accepted by industry” beyond the Appendix G part load curve, there have been some truly interesting discussions over these lists comparing notes!
>
> ~Nick
>
> NICK CATON, P.E.
> Owner
>
> Caton Energy Consulting
>    306 N Ferrel
>    Olathe, KS  66061
>    office:  785.410.3317
> www.catonenergy.com<https://mail.pathfinder-ea.com/owa/UrlBlockedError.aspx>
>
> From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Duggin, Cory
> Sent: Wednesday, September 02, 2015 3:43 PM
> To: Nicholas Blanton; Jim Dirkes
> Cc: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
> Subject: Re: [Bldg-sim] Fan power calculation for proposed model
>
> When I’m really interested in making sure my fan power is accurate, such as in lab buildings or anytime the fan energy is the predominant end use, I use the system break horsepower curve from the fan selection to build my own custom fan curve in the energy model.  I even look at my results to figure out what flow rates the fan operates at the most to specifically target those as points in my curve. As with many things, you could easily game the system.
>
> Cory Duggin, PE, LEED AP BD+C
> Associate/Energy Modeling Wizard, j.g.
> [GreenWeek2015_FINAL-Email-Sig]
> TLC Engineering for Architecture
> direct:
>
> 615-346-1939
>
>
>
> From: Nicholas Blanton [mailto:nicholas.blanton at arup.com]
> Sent: Wednesday, September 02, 2015 3:34 PM
> To: Jim Dirkes <jim at buildingperformanceteam.com<mailto:jim at buildingperformanceteam.com>>; Duggin, Cory <Cory.Duggin at tlc-eng.com<mailto:Cory.Duggin at tlc-eng.com>>
> Cc: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
> Subject: RE: [Bldg-sim] Fan power calculation for proposed model
>
> Cory/Jim,
>
> Because a fan selection only gives a single operating point for a specific system curve, I was interested in seeing if a proposed alternative, i.e. basing the system curve on a point produced by the simulation, could be a more accurate method of approximating fan energy consumption. But of course, the only known operating point for the fan is based on the fan selection.
>
> Given that this is the case, would you agree with me that there is no industry standard for establishing a fan power curve, for the purpose of energy modeling? Also, would you agree that the modeler could claim false savings based on a fan curve that contains low part load input kW? I am not aware of any requirements on the curve itself, and that is really the root of the issue I was trying to bring up.
>
> Thanks,
>
> Nick Blanton
>
> From: Jim Dirkes [mailto:jim at buildingperformanceteam.com]
> Sent: Wednesday, September 02, 2015 6:04 AM
> To: Duggin, Cory
> Cc: Nicholas Blanton; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
> Subject: Re: [Bldg-sim] Fan power calculation for proposed model
>
> I agree with Cory.
> The ASHRAE 90.1 committee would be hard pressed to integrate the different manners that all modeling software could be used to come up with specific simulated flow rates using unspecified (for the model) operating schedules and internal loads.  The designer is already tasked with selecting the fan using best available information, so I think that's a more reliable basis.
>
> On Tue, Sep 1, 2015 at 5:08 PM, Duggin, Cory <Cory.Duggin at tlc-eng.com<mailto:Cory.Duggin at tlc-eng.com>> wrote:
> It is my understanding that the proposed model should always be the design values used in selecting the fan not what is calculated by the energy simulation.  I agree the fan most likely will not operate at that flow rate, but that is what we have fan curves for.
>
> Cory Duggin, PE, LEED AP BD+C
> Associate/Energy Modeling Wizard, j.g.
> [GreenWeek2015_FINAL-Email-Sig]
> TLC Engineering for Architecture
> direct:
>
> 615-346-1939<tel:615-346-1939>
>
>
>
> From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Nicholas Blanton
> Sent: Tuesday, September 01, 2015 4:03 PM
> To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
> Subject: [Bldg-sim] Fan power calculation for proposed model
>
> Please comment on the following:
>
> Based on Table G3.1.10.a, for an HVAC system in the proposed design, the system is determined by the following:
>
> “Where a complete HVAC system exists, the model shall reflect the actual system type using actual component capacities and efficiencies.”
>
> In design of AHU systems, the scheduled or nameplate flow rate of the equipment is typically higher than the design flow rate of the system, as calculated by the simulation software. The system fan power calculation is based on the efficiency of the fan and ultimately the design flow rate of the fan. Also, in operation the fan typically does not operate at 60 Hz at peak flow rate, suggesting that the operating flow rate in this condition is more in line with the design flow rate calculated by the simulation software, rather than the nameplate flow rate of the equipment.
>
> For these reasons, it is likely the case that the fan power calculation should be based on the design flow rate calculated by the software, rather than the nameplate flow rate.
>
> Thanks,
>
> Nick Blanton
>
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>
> --
> James V Dirkes II, PE, BEMP, LEED AP
> CEO/President
> The Building Performance Team Inc.
> 1631 Acacia Dr, GR, Mi 49504
>
> Direct: 616.450.8653
> jim at buildingperformanceteam.com<mailto:jim at buildingperformanceteam.com>
>
> Website <http://buildingperformanceteamcom> l  LinkedIn<https://www.linkedin.com/pub/jim-dirkes/7/444/413>
>
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>
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