[Bldg-sim] Proposed Case fan power modelling

Wed Jul 19 21:53:58 PDT 2017

Thanks to Jim, Christopher, Patrick, Daniel and Nick for giving insight of
fan power modelling. What I understood from the conversation is: The fan
power consumption is the function of BHP and motor efficiency NOT the rated
motor HP.

Thanks again!

Regards,
Mayank

On Tue, Jul 18, 2017 at 10:32 PM, Nicholas Caton <
Nicholas.Caton at schneider-electric.com> wrote:

> Terminology can be a beast with fan/pump motor power calcs.
>
>
>
> “Fan absorbed power” isn’t a phrase I’ve encountered frequently but
> suggests to me work done by the fan on the air (or vise versa), presumably
> at design conditions for your case.  I would intuitively use this *in
> combination with* your knowledge of the nameplate HP rating to determine
> appropriate fan power inputs.  Leverage the nameplate HP rating of 7.5 to
> determine a reasonable motor efficiency first.
>
>
>
> So – quick aside for Recommended further reading:
>
> ·         The “I don’t have time!” suggestion:  Chapter 10 tables from
> 90.1
>
> ·         “Hit me with the good stuff!”  https://www.google.com/url?sa=
> t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwitnt6Y_
> ZLVAhUCeSYKHcRdCZ0QFggiMAA&url=https%3A%2F%2Fenergy.gov%
> 2Fsites%2Fprod%2Ffiles%2F2014%2F04%2Ff15%2Famo_motors_
> handbook_web.pdf&usg=AFQjCNE2OJ-TJR5_EFu34EoAiPO1PMP9BA
>
> ·         Highlights include:
>
> o   Table 3-3 detailing solid documentation for full load efficiencies
> for older large motors (excludes winding degradation losses for motors that
> haven’t been serviced).
>
> o   Table 2-1 should look familiar to those perusing 90.1 over the past
> decade.
>
> o   I recall on skimming today that Chapter 3 was super helpful for me
> learning to both digest and intelligently request direct measurements of
> operating motor performance in the field.
>
>
>
> So back to the problem.  Descriptively:  [Power In] = [Work accomplished
> by the fan: 4.73 bhp] / [Motor efficiency].  For a new motor that should
> lead you to something in-between 4.73 and 7.5 hp.
>
>
>
> Since you CC’ed eQuest-users specifically:  For developing eQuest inputs,
> additionally consider your flow rate associated with that design operating
> point to determine a kW/CFM input:  [kW/CFM] = 4.73* 0.7457 / motor-eff /
> CFM.  Best paired with a corresponding system design airflow rate input
> that isn’t getting overridden due to site elevation (air density) or zonal
> flow demands.
>
>
>
> A related nugget perhaps helpful to share, as this confused me for some
> years:  *motor efficiencies* in broad strokes do vary, but not much
> between 50-100% of nominal horsepower *load* with all else being equal
> (distinct from motor *speed*!).  It’s pretty normal to see motors
> “oversized/underloaded” motors with high nameplate horsepower relative to
> their actual full-load operating power requirement, and that isn’t
> necessarily a bad thing.  The above document includes some examples and
> further explanatory text illustrating where “right-sizing” a fan motor can
> result in identical or worse power input, where the points of efficiency
> gained for operating closer to full capacity are countered by the points of
> efficiency lost inherent to smaller motor sizes.
>
>
>
> ~Nick
>
>
>
> *Nick Caton, P.E., BEMP*
>
>   Senior Energy Engineer
>   Regional Energy Engineering Manager
>
>   Energy and Sustainability Services
>   Schneider Electric
>
> D  913.564.6361
> M  785.410.3317
> F  913.564.6380
> E  nicholas.caton at schneider-electric.com
>
> 15200 Santa Fe Trail Drive
> Suite 204
> Lenexa, KS 66219
> United States
>
>
>
>
>
> *From:* Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] *On
> Behalf Of *Jim Dirkes via Bldg-sim
> *Sent:* Tuesday, July 18, 2017 6:27 AM
> *To:* Mayank Bhatnagar <mayank.23aug at gmail.com>
> *Cc:* equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Proposed Case fan power modelling
>
>
>
> If the fan is using 4.73BHP, that's the value to consider for energy cost.
> It is very common for a motor to have greater capacity than is actually
> used.
>
>
>
> On Tue, Jul 18, 2017 at 7:24 AM, Mayank Bhatnagar via Bldg-sim <
> bldg-sim at lists.onebuilding.org> wrote:
>
> Hello Everyone,
>
>
>
>
>
> Ours is a Residential Project with PTAC units and DOAS in the Proposed
> design. The DOAS nameplate motor HP is 7.5 where as the fan absorbed power
> is 4.73 BHP. If we model 7.5 HP; we are falling short of the minimum LEED
> energy performance requirements. Modelling
>
> 4.73 BHP just gives us enough savings.
>
>
>
> Which one is the correct fan power to model?
>
>
>
> I have been through the archives and didn't find appropriate answer.
> Please help!
>
>
>
> Regards,
>
>
>
> Mayank.
>
>
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>
>
> --
>
> James V Dirkes II, CEO / President
> The Building Performance Team Inc.
> 1631 Acacia Dr, GR, MI 49504
>
>
>
> (alphabet soup of efforts for excellence: PE, BEMP, BCxP, LEED AP)
>
> Direct / Mobile: 616.450.8653
> jim at buildingperformanceteam.com
>
> Website <http://buildingperformanceteam.com>l  LinkedIn
> <https://www.linkedin.com/pub/jim-dirkes/7/444/413>
>
> *Coffee conversation:*
>
> They love truth when it enlightens them, they hate  truth when it accuses
> them… They love truth when it reveals itself, and hate it when it reveals
> them*.*
>
>
>
>
>
>
>
>
>
> .
>
>
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