[Equest-users] CFM/ton conflict issue for LEED projects

[Pasha Korber-Gonzalez]

I might also suggest doing a sensitivity analysis (trying a couple different
control options) ---on the air-side systems tab (under "Basic") there is a
sizing option, look in the bottom left corner where you can choose air
sizing based on "conincident" or "non-coincident" loads.   I'm guessing
yours is set to coincident which I believe is not the 'sum of the peaks'
option that your HVAC designer has based thier airflows on...   hope this
helps.

pkg

On Tue, Jul 20, 2010 at 7:55 AM, Bishop, Bill <wbishop at pathfinder-ea.com>wrote:

>  Mustafa,
>
>
>
> Short answer: No, you should not use the same system capacities or flow
> rates in your proposed and baseline designs.
>
>
>
> The baseline system airflow rates are calculated using a
> supply-air-to-room-air temperature difference of 20°F, per ASHRAE 90.1,
> Appendix G, G3.1.2.8.
>
> If the DESIGN-COOL-T of the zones is 75°F (the default), then the system
> MIN-SUPPLY-T should be 55°F.
>
> Use a system COOL-SIZING-RATI of 1.15, per G3.1.2.2.
>
> Make sure you have entered the minimum outdoor air ventilation rates and
> kept them identical between baseline and proposed models.
>
>
>
> While I have not tried it before, you may get higher baseline capacities by
> using the design day sizing option described in G3.1.2.2.1 instead of using
> the weather file.
>
>
>
> Usually, the cooling load in your proposed model will be less than the
> baseline, since your envelope will (hopefully) be improved and you will
> (hopefully) have a better lighting design.
>
>
>
> If you still show higher fan energy in the proposed model, and you are
> doing LEED v3, see if you can take advantage of any of the pressure drop
> adjustments listed in Table 6.5.3.1.1B.
>
>
>
> Regards,
>
> Bill
>
>
>
> *William** Bishop, PE**, BEMP, LEED® AP **|** **Pathfinder Engineers &
> Architects LLP***
>
> Mechanical Engineer
>
>
>
> 134 South Fitzhugh Street
> Rochester, NY 14608
> T: (585) 325-6004 Ext. 114
> F: (585) 325-6005
>
> wbishop at pathfinder-ea.com
>
> www.pathfinder-ea.com
>
> P Sustainability – less is more.
>  ------------------------------
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Mustafa
> Herzalla
> *Sent:* Tuesday, July 20, 2010 3:47 AM
> *To:* Equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] CFM/ton conflict issue for LEED projects
>
>
>
> Dear eQuest users,
>
>
>
> I calculate cooling load and design air flow using eQuest software then
> apply the  same design using HAP 4.3, the cooling load for the two designs
> in tonnage were the same, while the design air flow in CFM was in eQuest *
> less** *than the design air flow in HAP.
>
> For LEED projects, the proposed design should be model as the design
> documents, and many designers use HAP or other design software which is
> different than eQuest. and for LEED simulation we use eQuest , in this case
> the CFM/ton in the baseline design is less than the CFM/ton in the proposed
> design. The problem here that this case will reduce the energy savings in
> fans for the proposed design.
>
> My question is: is it ok to make the CFM/ton for the baseline design as in
> the proposed design? If NO, is there a solution to increase the design
> airflow for the baseline?
>
>
>
> Best,
>
> Mustafa Herzallah
>
>
>
>
>
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