[Equest-users] Does eQUEST derate equipment for altitude?

Aleka Pappas APappas at group14eng.com
Fri Jan 21 07:57:47 PST 2011


Hi Matt,
That's the same approach we take.  Then I double check to make sure the 
airflow rates in the HVAC summary report in eQuest match what the actual 
rates are.

*Aleka Pappas*
*Building Energy Engineer
**
GROUP14 ENGINEERING, INC. *
Inspiring better buildings.
1325 E. 16th Ave, Denver, CO 80218
Direct: 720.221.1082/ Main: 303.861.2070/Fax: 303.830.2016
<mailto:swagner at group14eng.com>
/Group 14 is the Carbon Group on the periodic table. Group14 Engineering 
offers building energy optimization, LEED coordination, commissioning, 
energy audits, LEED EBOM, and greenhouse gas analysis to reduce building 
and communities’ carbon footprint./

On 1/20/2011 5:55 PM, MattDubrovich at Eaton.com wrote:
>
> Unfortunately I think it might be more complicated than that; I wish 
> it wasn’t.  I have an old printout of an eQuest/DOE2 document called 
> “Sizing Air-Side HVAC Systems” which steps through the calculation.  I 
> haven’t been able to figure out where I printed it from (help file?, 
> dictionary? engineers manual?).
>
> My take is that eQuest sizes coils based on sea level airflow.  At the 
> end of the calculation it simply multiples the needed sea level 
> airflow by the altitude factor to account for altitude effects.  Per 
> Carol’s email, eQuest assumes any user entered flows are at sea 
> level.  This is frustrating because plans usually show airflows at 
> site altitude, not sea level.  We’ve tried Nick’s work-around which is 
> to change the altitude to 0 and enter airflows per the drawings.  This 
> works on the airflow side but not the coil side.  The coils are sized 
> using the entered airflow x 1.08 so eQuest creates coils that are 
> larger than what you actually have.
>
> What seems to be more correct is to keep the altitude specified and 
> divide every airflow you enter into the model by the altitude factor.  
> If you’re in Denver and want to model a 10,000 CFM fan, enter 
> 10,000/1.21 into the supply CFM input.  eQuest takes that number and 
> multiplies it by 1.21.  Every input with a “CFM” must be adjusted 
> including exhaust, CFM/SF, etc.
>
> *Matt Dubrovich, PE, CEM, BEMP
> *Energy Solutions Group
>
> *From:*equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Carol Gardner
> *Sent:* Thursday, January 20, 2011 1:22 PM
> *To:* Nick Caton
> *Cc:* equest-users at lists.onebuilding.org; Kendra Tupper
> *Subject:* Re: [Equest-users] Does eQUEST derate equipment for altitude?
>
> Nick/Kendra,
>
> The altitude factor effects the supply air and the outside air. The 
> write up below suggests that one calculate both supply and outside air 
> at sea level and then apply the altitude factor to it. In real life, 
> however, the design engineer is calculating and specifying supply and 
> outside air cfm that is already adjusted for the altitude and the 
> altitude factor should simply be set at 1.0 in eQUEST.
>
> The excerpts below discuss the areas of eQUEST impacted by the 
> altitude factor:
>
> Note: the quantities in this report (SV-A) have been adjusted for 
> altitude even though DOE-2 requires that any flows you enter in 
> SYSTEMS be at sea level.
>
> 1. SUPPLY FLOW
> is the calculated or user-specified supply flow for each zone.  Only 
> if you have specified a value for the ASSIGNED-FLOW keyword in the 
> ZONE command will the value here correspond to your input. The ZONE 
> keywords AIR-CHANGES/HR and FLOW/AREA will be accepted by SYSTEMS only 
> if they are consistent with the user-supplied HEATING-CAPACITY and 
> COOLING-CAPACITY and are equivalent to a flow larger than that of the 
> exhaust from or the ventilation to the zone. The ALTITUDE FACTOR will 
> be applied.
>
> 5. OUTSIDE AIR FLOW
> reflects the user-specified outside air quantity entered at the zone 
> level.  If OUTSIDE-AIR-FLOW is specified, its value is multiplied by 
> the ALTITUDE FACTOR and reported here.  Otherwise the reported value 
> is the maximum of the flow-equivalent values of OA-CHANGES and 
> OA-FLOW/PER, multiplied by ALTITUDE FACTOR.  For the actual amount of 
> outside air delivered to the zone for central systems, see OUTSIDE AIR 
> RATIO above.
>
> On Thu, Jan 20, 2011 at 10:49 AM, Nick Caton <ncaton at smithboucher.com 
> <mailto:ncaton at smithboucher.com>> wrote:
>
> Kenda,
>
> I’m curious as to whether you received any responses to the query below.
>
> I have incorporated a practice of manually setting the site altitude 
> in my eQuest models to “0,” because (1) as designers we do not specify 
> equipment with CFM’s at sea level, it is already “corrected” for 
> altitude in this sense, and (2) those who review models tend to miss 
> the significance of the altitude factor in the SV-A reports and 
> complain of incorrectly entered airflow rates.
>
> I don’t know if this constitutes a “best practice,” but I know it is 
> common to a number of the regular contributors to these lists besides 
> myself.  As it stands, current standards (90.1-2007) don’t have us 
> “de-rate” or otherwise adjust required minimum SEER/EER values for 
> altitude… so inversely it seem appropriate to remove the altitude 
> variable when modeling for a performance rating… thoughts?
>
> ~Nick
>
> cid:489575314 at 22072009-0ABB
>
> **
>
> *NICK CATON, E.I.T.*
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> www.smithboucher.com <http://www.smithboucher.com/>__
>
> *From:*equest-users-bounces at lists.onebuilding.org 
> <mailto:equest-users-bounces at lists.onebuilding.org> 
> [mailto:equest-users-bounces at lists.onebuilding.org 
> <mailto:equest-users-bounces at lists.onebuilding.org>] *On Behalf Of 
> *Kendra Tupper
> *Sent:* Thursday, September 02, 2010 1:53 PM
> *To:* equest-users at lists.onebuilding.org 
> <mailto:equest-users at lists.onebuilding.org>
> *Subject:* [Equest-users] Does eQUEST derate equipment for altitude?
>
> All,
>
> I'm trying to get clarification on exactly how eQUEST handles the 
> altitude above sea level that is entered in Site Parameters. My 
> understanding is this affects the airflow sizing calculations for cfm, 
> but does not change the hourly air density for all calculations. If 
> that is correct, then the altitude only corrects the cfms at the zone 
> and system level, but does not derate equipment efficiencies. So, if 
> you were to enter the altitude above sea level, you should then enter 
> your airflows at sea level, but enter all equipment efficiencies at 
> the derated conditions for that altitude.
>
> Is that correct?
>
> Kendra Tupper, PE, LEED AP
> Senior Consultant
> Built Environment Team
>
> Rocky Mountain Institute  |  T  303-567-8641 |  F  303-245-7213  | 
> www.rmi.org <http://www.rmi.org/>
>
>
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>
>
>
> -- 
> Carol Gardner PE
>
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