[Bldg-sim] Spam:Re: LEED NC Submittal Template, Heating/Cooling Hours Loads Not Met

ruju rathod ruju_r at yahoo.com
Thu Aug 21 16:23:19 PDT 2008


I have noted that the number of hours as per the % shown in the BEPS report is always slightly high than the actual. In a situation where you are close to 300 hours or 50 hours as applicable, it is best to check the SS-F reports and calculate the highest number of hours under-cooled or under-heated in any zone for each month. Adding the highest number for undercooled in each month for each zone and the highest number for underheated in each month for each zone will give the total number of unmet hours.
Consider only the highest number. Do not add all hours. That could be even higher than 8760.
Thanks,
Ruju Rathod.
Kirksey
www.kirkseygreen.com 



----- Original Message ----
From: Jay Keazer <JKeazer at tmecorp.com>
To: Dan Russell <danr at engineeringinc.com>; Brandon Nichols <BrandonN at Hargis.biz>; bldg-sim at lists.onebuilding.org
Sent: Thursday, August 21, 2008 4:15:30 PM
Subject: Re: [Bldg-sim] Spam:Re: LEED NC Submittal Template, Heating/Cooling Hours Loads Not Met

I am not certain, but I think the unmet load hours on the BEPS report is
consistent with the definition in Addendum a.  The BEPS report says "Percent
of hours any system zone outside of throttling range."  To me this is the
same as "one or more zones" being out of range for a particular hour.  

Adding up the unmet load hours of every zone would count a lot of coincident
unmet hours and could get large with a lot of systems (note this is what SS-R
does for multiple zone systems).  It could be greater than 8760, and I don't
think this is what appendix G is looking for.  If a lot of zones are out of
range during an hour (say an exceptionally cold night) that should only count
as 1 hour.

I don't think that the number on the BEPS is for the "worst case zone."  I
just checked a SIM file I had open and the BEPS report listed 3.3% unmet load
hours, so 289 hours (actually anywhere from 285-293).  Looking through SS-R
for each zone, the worst case had 177 hours under heated + 24 hours under
cooled, so 201 total unmet hours.

I have always gone by the BEPS (i.e. 3.4% or less is good), but have never
known how to find more detailed output regarding how many are cooling vs. how
many are heating.  Theoretically I think you could do this with an hourly
report for every zone and some postprocessing, but I don't really want to go
there.  Anybody have a more practical approach?


Jay Keazer,  EI
Energy Engineer
TME, Inc.
2039 N Green Acres Road
Fayetteville, AR  72703
 
ph   479.521.8634
fax  479.521.1014
jkeazer at tmecorp.com
www.tmecorp.com



-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dan Russell
Sent: Thursday, August 21, 2008 1:12 PM
To: Brandon Nichols; bldg-sim at lists.onebuilding.org
Subject: Spam:Re: [Bldg-sim] LEED NC Submittal Template,Heating/Cooling Hours
Loads Not Met

Brandon, I have been on the same page regarding this issue, and have
submitted for successful LEED certifications using those assumptions ...
until I read Addendum a to 90.1-2004, which adds the definition of
"unmet load hour" to Section 3.2.  The definition is:

unmet load hour: an hour in which one or more zones is outside of the
thermostat setpoint range.

Unfortunately this seems to clearly indicate the unmet load hour value
asked for refers to all zones at once.  

My previous assumptions to only consider the worst-case zone were based
on the example set forth by the USGBC's document titled "Example LEED-NC
v2.1 Energy & Atmosphere Credit 1 Submittal", which I referenced back
when I did my first LEED submittal in 2005.  This document is still
available from their server at the following address:

http://www.usgbc.org/ShowFile.aspx?DocumentID=2423

This document uses the following paragraph to demonstrate compliance
with the unmet load hour requirement:

"The worst-case zone in the budget case is a North classroom. This zone
is under-heated 40 hours out of the year in the Energy Cost Budget case
and 0 hours per year in the Design Energy Cost case. This is within the
50 hour per year limit required by ASHRAE 90.1-1999."

Now, if Addendum a were not used in any part as basis for LEED submittal
one could possibly argue using the quoted precedent above.  Granted, the
above precedent applied to the 1999 version of 90.1 and the 2.1 version
of LEED, but it seems to reasonable that the implications made there
should carry over until otherwise directed (as in Addendum a).
Furthermore, it is my opinion that 90.1-2004 (not including addendums)
does not clearly resolve the issue.  The ASHRAE technical committee must
have agreed, hence the inclusion of the new definition for "unmet load
hour" in Addendum a.

So, if Addendum a is not used, there may be a possibility to consider
unmet load hour only on a worst-zone basis.  However, if Addendum a is
used it seems clear that the unmet load hour applies to all zones at
once.

Certainly larger project simulations with multiple zones will suffer
from this added definition.

Thanks,

Dan Russell, EIT 




-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Brandon
Nichols
Sent: Thursday, August 21, 2008 11:22 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] LEED NC Submittal Template,Heating/Cooling Hours
Loads Not Met


All,

"Table 1.3 -- Advisory Messages" of the LEED NC Submittal Template
requests "number of hours heating loads not met" and "number of hours
cooling loads not met".  We've taken a vote here in the office, and its
2-0 in favor of reporting the worst case zone as shown on the BEPS
report.

But we have some lingering doubts... can anyone say definitively what
numbers are being asked to for here?  our runner-up in the voting was
the total of all zone hours out of throttling range -- however this
could easily exceed the limit of 300 hours on a large project with many
zones.  

As 300 hours is less than 5% (3.4% actually) of 8760, we think that the
300 hours is "per zone", not a total limit for the entire project.  

Comments appreciated....
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