[Bldg-sim] Fan power calculation for proposed model

Wed Sep 2 15:11:12 PDT 2015

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

*From:* Bldg-sim [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
*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.*

*[image: GreenWeek2015_FINAL-Email-Sig]*

*TLC Engineering for Architecture *

direct:

615-346-1939

*From:* Nicholas Blanton [mailto:nicholas.blanton at arup.com
<nicholas.blanton at arup.com>]
*Sent:* Wednesday, September 02, 2015 3:34 PM
*To:* Jim Dirkes <jim at buildingperformanceteam.com>; Duggin, Cory <
Cory.Duggin at tlc-eng.com>
*Cc:* 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
<jim at buildingperformanceteam.com>]
*Sent:* Wednesday, September 02, 2015 6:04 AM
*To:* Duggin, Cory
*Cc:* Nicholas Blanton; 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>
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.*

*[image: GreenWeek2015_FINAL-Email-Sig]*

*TLC Engineering for Architecture *

direct:

615-346-1939

*From:* Bldg-sim [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
*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

____________________________________________________________
Electronic mail messages entering and leaving Arup  business
systems are scanned for acceptability of content and viruses

_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to
BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG

-- 

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

Website <http://buildingperformanceteamcom>l  LinkedIn
<https://www.linkedin.com/pub/jim-dirkes/7/444/413>

The body must be given a little less than it needs. Otherwise it will turn
traitor.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20150902/1d332b5d/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 6387 bytes
Desc: not available
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20150902/1d332b5d/attachment-0003.jpg>