[Equest-users] One more fan power EIR and DCV question

[Robby Oylear]

Hi Laura,

This sounds a lot like what we typically do for garage ventilation CO
control.  What you're describing would fall under an Exceptional
Calculation Method per ASHRAE 90.1-2007 G2.5.

I would agree that this is a valid energy savings strategy, but it should
not be presented as part of your base savings.  You should model it as an
ECM under the appropriate section of the submittal template.  Show the
savings of this ECM and provide supporting documentation that shows that
you have modeled the system appropriately to how it will actually be
operated (i.e. justify your hourly DCV schedule).  In this manner, if the
reviewer chooses not to accept your modeling methodology, they will award
you only the base level of savings and you will not have further review
comments holding up your project.

Robby Oylear, P.E., LEED AP

*Mechanical Engineer*

*Senior Energy Analyst*

* *

*D* 206-788-4571

*www.rushingco.com* <http://www.rushingco.com/>

On Fri, Jun 15, 2012 at 11:30 AM, Laura Howe, RCE <
laurahowe.rce at qwestoffice.net> wrote:

> HI Again all-****
>
> ** **
>
> Thanks for everyone for their assistance earlier this week, it really
> helped me progress with this model adjustment.  I am currently at another
> dilemma.  This is DCV not for typical occupancy, but for ventilating
> infrequent diesel fumes.****
>
> ** **
>
> I have two systems modeled as one, a constant volume packaged unit along
> with an exhaust system (no heating/cooling).  The exhaust system will
> operate separate from the packaged unit and the proposed case includes a
> fraction in the operation schedule to reflect DCV operation.  That schedule
> doesn’t affect the package unit except it will have less heating/cooling
> load due to the DCV.  I don’t see the DCV affecting the fan sizing or
> operation of the baseline packaged unit.  The packaged unit is constant
> volume.  So, the LEED comments refer to identically modeling the base and
> proposed systems, for fan volume and fan power, on this exhaust system.
> I’ve worked out matching the exhaust system well enough, but now I’m
> wondering if I need to match the supply also.  The simplistic answer would
> be “yes”, even if the comments refer only to the exhaust system I am
> concerned a cursory review may still not be happy with the supply fan
> volume/power not matching.  I think not matching is valid and it is
> definitely more favorable, so that’s what I’d rather do.****
>
> ** **
>
> The baseline system has a larger supply fan, and will have a greater
> heating/cooling load (no DCV).  The proposed system will have a smaller
> supply fan and a smaller heating/cooling load.  I think the base case fan
> sizing is more accurate since it is based on the actual loads of the
> baseline building.  If I use the fan sizing/power from proposed, the
> project will take a big hit.  Basically I think this means in theory that
> not matching the supply fans, even though they are tied to the exhaust DCV,
> is an accurate estimation of savings from baseline to proposed.****
>
> ** **
>
> Right now I’m inclined to leave the supply not matching, and provide an
> explanation.  However since there has already been one review, I don’t like
> the potential that they will just come back with a response of eliminating
> a certain number of points.  If they don’t think my response is adequate, I
> don’t think they will give me another chance, correct?****
>
> ** **
>
> For those that requested their actual response, I finally got my hands on
> a document I could copy text:****
>
> ** **
>
> **1.      **“The Baseline fan power calculations and the SV-A reports for
> the Baseline model indicate that the exhaust fan systems (SF-1 and SF-2, as
> indicated in the mechanical schedules provided for PI Form 4: Schedule and
> Overview Documents) have not been modeled identically in the Proposed and
> Baseline cases. All independent fan systems of the HVAC systems in the
> actual design must be modeled identically between the Proposed and Baseline
> models at actual equipment capacities (fan volume and fan power) as
> required by Table G3.1.10 in the Proposed building column, since the fan
> design air flow rates and fan power per Sections G3.1.2.8 and G3.1.2.9,
> respectively, only applies to system types 1 through 8 in Table G3.1.1A.
> Revise the Proposed and Baseline model so all independent fan systems of
> the HVAC systems are modeled identically between the Proposed and Baseline
> model. In addition, provide revised SV-A reports for the Proposed and
> Baseline model reflecting the changes. ****
>
> ** **
>
> Thoughts?  Must I go simplistic and make supply match?  Am I offbase
> thinking not matching is a valid energy consumption model comparison?****
>
> ** **
>
> Thanks****
>
> Laura****
>
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