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

Eurek, John S NWO John.S.Eurek at usace.army.mil
Tue Oct 11 06:58:05 PDT 2011


Classification: UNCLASSIFIED
Caveats: NONE

I do not use the peak/design in my models.  I have modeled a lot of churches.
A sanctuary may be able to seat 600 people, the HVAC may be sized to handle
600 people, but it is very defensible to assume that the church won't be all
full capacity every Sunday.  (I always double check that the system can
handle Christmas and Easter, but I don't even add those two days to the 8760
energy model.)



-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bobby Sy
Sent: Saturday, October 08, 2011 1:40 PM
To: Nick Caton
Cc: Equest-users at lists.onebuilding.org; Jiao, Joey
Subject: Re: [Equest-users] Values choosing of the typical equipment
&miscellaneous power densities.

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

	 

	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 <http://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

	 

	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 <http://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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Classification: UNCLASSIFIED
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