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

Demba Ndiaye demba.ndiaye at setty.com
Fri Aug 22 15:08:00 PDT 2008
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I think the "Percent of Hours Any System Zone Outside of Throttling
Range" is rather the number of hours for which there is at least one
under-cooled or under-heated zone divided by 8760 (the eQuest commented
reports I have indicate that "The denominator used for this %
calculation is always 8760.")

 

______________

Demba Ndiaye

________________________________

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of gaurav
mehta
Sent: Friday, August 22, 2008 4:19 PM
To: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Spam:Re: LEED NC Submittal
Template,Heating/Cooling Hours Loads Not Met

 

There are two things that need to be separated.

1.	What are the Appendix G requirements for "unmet load hours"
2.	Where does one find the information from the output report of
the software? 

  

1. Appendix G requirements

 

The main purpose of this requirement is to ensure that the equipment is
not undersized and does not result in too high unmet load hours.
Undersized equipment consumes less energy along with resulting in large
unmet load hours (depending upon the location). Moreover, if the
difference between the baseline and proposed unmet load hours is high,
it can either penalize or benefit the savings (hence the requirement
that the difference shall not exceed 50 hours between the baseline and
proposed case).

 

When one sizes equipment, it is done for the worse case scenario,
meaning if it can meet the loads of the worst zone then it would be able
to meet the loads of other zones. Therefore, looking at the worst zone
would make sense.

 

Having said that, one also needs to keep in mind, there are various
building types using a variety of HVAC systems that use Appendix G. Some
are 24/7 facilities and some are schools or offices, etc. Some use zonal
systems and some have an AHU per floor or one AHU for the whole
building. I am not an authority on Appendix G, however, to me it seems
appropriate that the Appendix G requirement is for the whole project and
not for the worse zone.

 

For a large project, with large number of zones, the total unmet
cooling/heating hours can well exceed 8760. If this is what the
simulation results show then it is an indication-either the system is
highly undersized or there is something wrong with how the system has
been modeled or both!

 

As a practice, I always look at the SS-R reports and add the unmet
cooling hours for the whole project and I maintain them well below 300
and similarly I add all the unmet heating hours and maintain the total
well below 300 for the whole project. And I also make sure that the
difference between both the proposed and baseline is below 50 fro both
heating and cooling. I formed this habit when I was single and I didn't
have a life. Although I am married now, but I still maintain this habit
(till my wife threatens to abandon me!)  

 

 

2. Output from the simulation software (eQuest)

 

The BEPS/ BEPU reports show the worst zone scenario. Please look at SS-R
report; identify the worse zone- (the zone which has the largest unmet
load hours, determined by adding the unmet cooling and heating hours).
Add unmet cooling hours and unmet heating hours of this zone, divide
this number by the Total Run Hours also shown on the SS-R report and
calculate the percentage. The same percentage is reported on the BEPS/
BEPU reports as "Percent of Hours Any System Zone Outside of Throttling
Range".

 

The total run hours in the SS-R report equal the hours the fan operate
(for a typical office building the fans run 11 hours each day from 7am
to 6pm). Typically it would be ~2761 hours and not 8760 hours based upon
the following formula:

11hrs * 5 days/week * 52 weeks a year - 11hrs * # of holidays + # of
hours during the unoccupied hrs when fans turn on to maintain setback
temperature.

 

 

Thanks and Happy Friday!

 

Best regards,

 

 

Gaurav Mehta



 

On 8/22/08, May Xu <may.xu at hok.com> wrote: 

The definition of "unmet load hours" in Edition 3 of LEED-NC 2.2 (page
187) is "occupied periods where any zone is outside its temperature
setpoint". I noticed the words "occupied period". Does it mean the unmet
hours in "non-occupied periods" (e.g. at mid-night when no people in the
building) can be excluded? If I am right, the % in BEPS report counts
both occupied period and non-occupied period.

May

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Friday, August 22, 2008 2:44 PM
To: Michael Tillou
Cc: bldg-sim at lists.onebuilding.org; 'Brandon Nichols'
Subject: Re: [Bldg-sim] Spam:Re: LEED NC Submittal Template,
Heating/Cooling Hours Loads Not Met

I have always looked at the SS-F report. Does any one else use it?


Michael Tillou wrote:
> If you're using eQuest the Air Side Summary report in the eQuest
interface
> has all that info.  It is also reported in SS-R Zone Performance
Summary in
> the .SIM file.
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jay
Keazer
> Sent: Thursday, August 21, 2008 5:16 PM
> To: Dan Russell; Brandon Nichols; bldg-sim at lists.onebuilding.org
> 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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