[Equest-users] Values choosing of the typical equipment &miscellaneous power densities.

[Bobby Sy]

Hi all,

Thank you guys for bringing this up.

I'd like to ask a simple question about the occupancy assumption. Do we need
to match the occupancy density to the assumed occupancy (usually peak or
dense) by the HVAC designer, in the model? Often times HVAC designers assume
more occupants for peak load.

I understand that simulation needs to be close to reality as possible but if
I will reduce the occupancy close to reality, savings may be reduced due to
increase in the HVAC equipment capacity difference between the baseline &
proposed because the baselines equipment will be auto-sized (1.15 ratio for
cooling, 1.25 for heating).

Have you experienced a comment from a reviewer picking on inconsistencies on
assumed occupancy between other credit/prerequisites?

Thanks,
Bob


2011/9/29 Nick Caton <ncaton at smithboucher.com>

> Hi Joey,****
>
> ** **
>
> I thought to write about the 25% topic but thought it best to not bring it
> up¡­  Perhaps a quick recap is in order for your situation and others¡¯
> benefit!****
>
> ** **
>
> There has been much discussion regarding that ¡°25% rule¡± between myself and
> others on these lists ([bldg-rate], [bldg-sim], [equest-users]).  Re:
> archives.****
>
> ** **
>
> I started out with the same conclusion you¡¯re stating: the baseline
> consumption is supposed to be 25% plug/process loads.  The LEED 2.2 handbook
> is unfortunately worded under EAc1 to suggest this as a prescriptive default
> in the absence of substantial documentation, but that ¡°documentation¡± can be
> as simple as a one-line reference as I described.  Note the LEED v3 handbook
> (under EAp2 I think) re-words those lines on process loads to emphasize the
> expectation is to simply match between the models ¨C no mention of 25%.  **
> **
>
> ** **
>
> I have since that time done an about face on that viewpoint and believe
> that figure to be entirely arbitrary.  ¡°Forcing¡± 25% plug load consumption
> in the baseline is in many cases arbitrarily detrimental to the overall
> performance rating, is rarely realistic, and the resulting internal gains
> can cause irresolvable unmet hours for proposed equipment of a specified
> capacity (remembering the baseline and proposed should normally have
> matching process loads).  I came to the lists seeking to share and learn
> better approaches to ¡°fairly¡± mitigate these artificial internal loads, and
> in doing so learned I was far off the path from others.****
>
> ** **
>
> I could re-iterate my perception of the history and intent behind the 25%
> figure, but you¡¯re probably best advised to seek out those discussions in
> the archives to come to a fuller understanding.  I would presently advise
> referencing and using something *reasonable* for your proposed building in
> both models, and not treating the 25% figure as a mandate, but do inform
> yourself by reading those archived discussions so that you can defend your
> position against any argumentative v2.2 reviewer.  ****
>
> ** **
>
> ~Nick****
>
> ** **
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, P.E.***
>
> SENIOR ENGINEER****
>
> ** **
>
> Smith & Boucher Engineers****
>
> 25501 west valley parkway, suite 200****
>
> olathe, ks 66061****
>
> direct 913.344.0036****
>
> fax 913.345.0617****
>
> www.smithboucher.com* *****
>
> ** **
>
> *From:* Jiao, Joey [mailto:Joey.Jiao at WSPGroup.com.cn]
> *Sent:* Wednesday, September 28, 2011 9:56 PM
> *To:* Nick Caton
> *Subject:* ´ð¸´: [Equest-users] Values choosing of the typical equipment
> &miscellaneous power densities.****
>
> ** **
>
> Hi, Nick:****
>
> Thank you for your suggestion , it¡¯s really helpful!****
>
> I have found the TABLE GB, in ASHRAE 90.1-2007 Manual. See it below. I
> think it¡¯s what¡¯s your refer to.****
>
> As an addition,  I get another tip which should be a limitation for making
> a baseline model. ****
>
> On the LEED RATING SYSTEM , there is a rule that the process energy cost
> should be 25% of the total baseline energy cost. ****
>
> Hope it helpful for others.****
>
> Thanks for your help again.****
>
> ** **
>
> Joey****
>
> ****
>
> *·¢¼þÈË**:* Nick Caton [mailto:ncaton at smithboucher.com]
> *·¢ËÍʱ¼ä**:* 2011Äê9ÔÂ28ÈÕ 22:48
> *ÊÕ¼þÈË**:* Jiao, Joey; Equest-users at lists.onebuilding.org
> *Ö÷Ìâ**:* RE: [Equest-users] Values choosing of the typical equipment
> &miscellaneous power densities.****
>
> ** **
>
> Generally, the ¡°correct¡± baseline model values for these entries (misc/plug
> loads and occupancy/ventilation) are to match whatever is in the proposed
> model.****
>
> ** **
>
> There is more than one ¡°correct¡± approach regarding misc load quantities
> for the proposed model.  In any case you should be prepared to reproduce
> what decision you made and back it up for baseline/proposed documentation:
> ****
>
> **-          **Reference tables in the 90.1 users manual (also found in
> certain state energy codes) with representative W/SF figures for various
> ¡®whole building¡¯ types and assign that figure to each space.  I¡¯ve found
> this approach to be time-efficient and so far totally accepted by the
> USGBC/LEED reviewers.****
>
> **-          **Stick with the eQuest defaults per occupancy.  I¡¯m unsure
> of where they¡¯re all derived from exactly (Title 24?  Some other
> standard/reference?), but they will vary as you change space activity types
> and appear sensible from what I¡¯ve observed.  These values, default or
> otherwise, are rolled into a weighted average for each zone group based on
> the % distribution in the zone group screen ¨C which is why the resulting
> W/SF coming out of the wizards can appear somewhat random at first glance.
> ****
>
> **-          **Flex your spreadsheet muscles and do a space-by-space plug
> load takeoff to come up with an ¡°actual¡± number.  I have never pursued this
> degree of detail myself, but I understand others have specifically to
> account for gains from providing efficient plug load equipment with the
> project over ¡°standard¡± equipment¡­ resulting in a deliberate divergence
> between the baseline/proposed models. ****
>
> ** **
>
> I¡¯ve found eQuest default values for occupant density/ventilation/loads are
> pretty much on the mark as to what I¡¯d define from ASHRAE references, so I
> leave the defaults alone in wizards and only focus on tweaking the
> calculated zone occupant quantities in detailed mode as necessary for model
> QC and matching loads.  I do make a point to assign the appropriate ¡°space
> type percentages¡± for each zone in the following wizard screens however.**
> **
>
> ** **
>
> ~Nick****
>
> ** **
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, P.E.*
>
> SENIOR ENGINEER****
>
> ** **
>
> Smith & Boucher Engineers****
>
> 25501 west valley parkway, suite 200****
>
> olathe, ks 66061****
>
> direct 913.344.0036****
>
> fax 913.345.0617****
>
> www.smithboucher.com* *****
>
> ** **
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Jiao, Joey
> *Sent:* Wednesday, September 28, 2011 4:59 AM
> *To:* Equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Values choosing of the typical equipment
> &miscellaneous power densities.****
>
> ** **
>
> Hi, Everyone:****
>
> I¡¯m confused with the value choosing for the equipment & miscellaneous
> power densities like the illustrate below.****
>
> The table G 3.1 no.12 said it should be based on the building and space
> type, but there isn¡¯t other information. So do we need to add this load part
>  when we make a baseline model? ****
>
> Maybe this isn¡¯t very important , but I want to make sure about it.****
>
> I know we can choosing the lighting power densities in Section 9, but I
> can¡¯t find the table for other equipment. So what should you do?****
>
> ****
>
> ** **
>
> By the way , about the occupancy density and ventilation inputs shown
> below, I found  the reference information from ASHRAE 62.1, is that a common
> way when we make a baseline? ****
>
> ****
>
> Thank you for your kindly help.****
>
> Best wishes.****
>
> ** **
>
> Joey****
>
> *
> ---------------------------------------------------------------------------
> *
>
> *Joey Jiao*
>
> *Graduate Engineer         ***
>
> ** **
>
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