[Equest-users] Confirmation for finding the Baseline Energy Model Supply Airflow

[Carol Gardner]

That sounds to me exactly like what you should do. The baseline fans running
more often signals they are too small to meet the load. As you increase the
cfm/sf I would guess that eQUEST will respond accordingly and the fans will
get bigger and life will be beautiful all the time. Trees, flowers, chirping
birds....Oops, I forgot this is a professional listserv.

Regards,
Carol

On Wed, Sep 8, 2010 at 6:47 AM, Otto Schwieterman <oschwieterman at fhai.com>wrote:

>  Appendix ASHRAE 90.1 2007 Appendix G3.1.3.13 VAV Minimum Flow Setpoints
> (System 5 and 7) states:
>
>
>
> “Minimum volume setpoints for VAV reheat boxes shall be 0.4 cfm/sf of floor
> area served or the minimum ventilation rate, whichever is larger.”
>
>
>
> For systems 5 & 7, I will set the minimum flow rate to 0.4 CFM/SF. If I
> have high unmet hours due to the small amount of CFM, I will increase the
> value on a room by room basis. The baseline’s flow rates are typically 30%
> less than my proposed model. The fans typically run more often in the
> baseline model.
>
>
>
> Does anyone else have a different way to model the flow rates for the LEED
> Baseline model?
>
>
>
> *From:* Carol Gardner [mailto:cmg750 at gmail.com]
> *Sent:* Tuesday, September 07, 2010 9:02 PM
> *To:* Kathryn Kerns
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Confirmation for finding the Baseline Energy
> Model Supply Airfllow
>
>
>
> You must use the 1.15 and 1.25 multipliers to meet LEED requirements. I
> would look at the throttling range that eQ is defaulting to. if it's .5 F,
> which is I think what it is for PSZ, I would raise that to1 or 2 F, which is
> reasonable. Then I would look at the space loads, equipment especially and
> make sure all that looks good, then I'd look at the schedules, make sure
> they are good, and then I'd look at the cfm/sf. It's not unreasonable to
> match it to your proposed building and I don't know of any issue LEED has
> with doing that.
>
> Carol
>
> On Tue, Sep 7, 2010 at 4:23 PM, Kathryn Kerns <
> kathryn.kerns at bceengineers.com> wrote:
>
>
>
> Yes, Carol I know the default airflow value is very low. Usually the eQuest
> airflow auto sizing routine will select larger values than the default. The
> problem is: what if the eQuest baseline energy model selects airflows larger
> than the default cfm/sqft airflow values but the baseline energy model still
> ends up with greater than 300 unmet hours or the baseline energy model has
> more than 50 unmet hours greater than the proposed energy model?
>
>
>
> Do you start increasing the baseline energy model airflows above the auto
> sized airflow value in the thermal blocks that are having unmet hours
> issues, or do you retain the auto sized airflow value and start manually
> increasing the baseline heating and cooling capacities that were also auto
> sized by eQuest using the 1.15 and 1.25 oversized coefficients?
>
>
>
>
>
> *Kathryn Kerns*
>
> *Systems Specialist*
>
> *BCE** Engineers, Inc.*
>
> *| Ph: 253.922.0446 | Fx: 253.922.0896 |*
>
>
>
>
>   ------------------------------
>
> *From:* Carol Gardner [mailto:cmg750 at gmail.com]
> *Sent:* Tuesday, September 07, 2010 2:22 PM
> *To:* Kathryn Kerns
>
>
> *Cc:* equest-users at lists.onebuilding.org
>
> *Subject:* Re: [Equest-users] Confirmation for finding the Baseline Energy
> Model Supply Airfllow
>
>
>
> Kathryn,
>
>
>
> I think that .5 cfm/sf is too low. I never saw it used when I was designing
> HVAC systems except for an occasionally used interior space. I immediately
> change it to1.0 cfm/sf which I feel is a good place to start. For highly
> loaded rooms with lots of internal gain I sometimes up that amount after I
> have checked the other possible inputs.
>
> Carol
>
> On Tue, Sep 7, 2010 at 1:55 PM, Kathryn Kerns <
> kathryn.kerns at bceengineers.com> wrote:
>
>
>
> Everyone,
>
>
>
> We are having a discussion at the office about how to define the supply
> airflow and energy model baseline. I pick the baseline system type per
> Appendix G (packaged single zone, packaged VAV, etc., set the heating sizing
> ratio to 1.25 and the cooling sizing ratio to 1.15, leave the heating and
> cooling capacities blank so the model will auto-size, and then set the
> default airflow to 0.5 cfm/sqft and let eQuest run. I then check to see if
> the baseline energy model unmet hours are less than 300 and are within 50
> hours of the proposed model. If the baseline energy model is above 300 unmet
> hours or isn’t within 50 hours of the proposed model, I will then start
> tweaking the airflow in the baseline energy model thermal blocks that are
> causing the unmet hour issues to solve the problem.
>
>
>
> Is this what everyone else is doing or do leave the airflow with the
> default values it calculated with the 0,5 cfm/sqft limit and enter capacity
> values in the previously blank HVAC cooling and heating capacities slots so
> the baseline energy model stops auto-sizing?
>
>
>
> Thanks.
>
>
>
>
>
> *Kathryn Kerns*
>
> *Systems Specialist*
>
> *BCE** Engineers, Inc.*
>
> *| Ph: 253.922.0446 | Fx: 253.922.0896 |*
>
>
>
>
>
>
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>
>
> --
> Carol Gardner PE
>
>
>
>
> --
> Carol Gardner PE
>
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-- 
Carol Gardner PE
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