Reproducing Unmet Hours

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It seems I spend a great deal of time with eQuest trying to reduce unmet
hours in a model. One thing I?ve tried is having eQuest produce an hourly
report of a problem zone?s temperature and T-stat setting, exporting the
data to Excel and then searching it for patterns. This approach has a few
problems:

1. I can barely figure out how to create the hourly report I?m looking for.
The reporting function (in the Detailed Data Edit mode, under Project &
Site, Hourly Reports) isn?t very intuitive, and I can?t find any
documentation on it. Has anyone found the docs on this? (I?m currently
working through the relevant sections of the DOE 2-2 Dictionary, trying to
cross reference between the inputs to eQuest and the BDL file generated from
those inputs. I?m just wondering if there?s a short-cut somewhere.)
2. Once I get the data in Excel and do some filtering, I can never get the
exported data to match the unmet hours found in report SS-R. The Excel
analysis seems to always overstate the unmet hours. Has anyone had any luck
reproducing the SS-R values? Any ideas?
3. I?d like to hear other user?s experience. Do you find that resolving
unmet hours is a significant part of your modeling time?

Steve Samenski, PE, LEED AP

STEVE SAMENSKI's picture
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Steve:

The NO. 1 thing I have found effective is to increase the deanband in the thermostat. I don't thin USGBC has any problem with that.

It also depends on wheather it is COOLING or HEATING unmet housers. Sometimes, you haven't provided a reheat vaule.

Try those first.

John Aulbach's picture
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Steve

As far as I know you get an hourly temperature overview of your conflict zone in the SS-O report of the Simulation Output

Regards,

Francisco Aguirre (Curro)

Francisco Aguirre's picture
Joined: 2011-09-30
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Francisco ? thanks for responding. Yes, Report SS-O gives you an hourly
summary. The operating hours are divided into 5 degree bins, and this can?t
be changed. I?ve found SS-O useful in two cases:
1. Diagnosing a case where a unit is undersized. (I work in a cooling
climate.) SS-O will show a nice ?bell curve? peaking at or just past the
hottest part of the day.
2. Diagnosing an instance where the AC units aren?t starting up early enough
in the morning.

The situation with my current model is a bit different. The design engineer
has placed two thermal zones on opposite exposures (east and west) of the
building. I can?t get the system satisfied, despite the fact that it?s
large enough. Whichever zone has the T-stat is mostly (but not completely)
satisfied. I believe the two zones won?t be happy on the same AC, so I
wanted to prove that with an hour by hour analysis, contrasting the peak
temperatures for each zone.

I?m going to try expanding the throttling range as recommended by John A. in
a previous response. However, I?m not completely sure that each thermal
zone can have it?s own T-stat.

Steve Samenski, PE, LEED AP

STEVE SAMENSKI's picture
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By dead band, do you mean the throttling range that eQuest defines? If so, there is a limit on how much you can increase it, due to the 5F minimum dead band requirements of the 90.1.

Demba.

Demba Ndiaye's picture
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John ? thanks for the tip on the throttling range. I was able to reduce the
unmet hours by increasing the range from 2 degrees to 4 degrees in the
perimeter zones.

Demba ? As I read the help file, the throttling range is the same as the
dead band described in in 6.4.3.1.2 of Standard 90.1.

?The number of degrees that room temperature must change in order to go from
full heating to zero heating or from full cooling to zero cooling. The zone
temperature heating or cooling set point is assumed to be at the midpoint of
the throttling range. This keyword is appropriate to THERMOSTAT-TYPE =
PROPORTIONAL or REVERSE-ACTION only. ?

Since the heating or cooling setpoint is assumed to be at the midpoint of
the throttling range, then a throttling range of 10 degrees would correspond
to a dead band of 5 degrees. Maybe tomorrow I?ll see what that does to my
results.

Steve Samenski, PE, LEED AP

STEVE SAMENSKI's picture
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Steve,

My understanding is that deadband is not the same as throttle range.
Deadband is the temperature range between the system being cooling to
heating. See attached to clarify.

Regards

Francisco

Francisco Aguirre's picture
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Sorry - I "misspoke." Throttling range is correct.

John Aulbach's picture
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