Unmet hours

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Dear all,

I am having 19.2% of hours outside throttling range, and the fans are on for 8760 hrs (all the year). This means 1682 hrs outside throttling range. How can I reduce this number to less than 300? I increased the chiller and boiler capacities a lot, (from 0.6 to 65 MBtu/h), but it seems there is a limit on the effect of capacities on the hours unmet.

Does anyone know how I can solve this problem? Is there any other parameter i need to play with to decrease the number of unmet hours?

Many thanks,
Omar

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Omar Katanani

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if you're using vav reheat make sure your heating schedule is for
"hourly report" not the "heating schedule" assigned to your hvac units.
you might not be getting any reheat outside of winter months when it may
be needed.

Patrick J. O'Leary, Jr.'s picture
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Yes, your temperature set points, and throttling range (dead band). A
quick lean explanation. Standard eQuest throttling range is 4F.
Throttling hours are in 5F bands , 65, 75 and 80 being the critical
bands for unmet hours. Typical buildings are controlled at 70F for
heating and 75 for cooling aligning with the cut-off points not the
midpoints of the critical bands. A little conflict. Solutions, make
your throttling range larger, 5 or 6 degrees normally will do it. You
can also modify your set points say to 68F heating and 78F cooling,
69/76. You just have to play with it a bit but normally the throttling
range will do it. The help file will provide more info on dead band and
throttling range.
Bruce Easterbrook P.Eng.

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Dear all,

I have another scenario whereby I have 100% of the hours unmet. What is wrong? I do not think that playing with the throttling range will fix this huge number.

Please find attached my files. Can someone help me? It is very urgent and I already passed the deadline.

I am getting average zone temperatures of 90F, where my set points are 72-75!

I really appreciate your feedback. Please can someone check the thermostat schedules, the cooling/heating setpoints, or any other item you find worth checking? Much appreciated!

Many thanks,
Omar
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Omar Katanani

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Omar,

You have 149 errors in your model and some strange things occurring. For
instance, I cannot see your information using the spreadsheet option which
would be the easiest way to fix what I suspect might be wrong.

Take a look at your .bdl file and find out what all those errors are. After
you take your best shot at fixing them send the files again and I will look
at them. I suspect that the errors are disabling the spreadsheet option
somehow.

Carol

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Hi All,

I am trying to determine the number of unmet cooling and heating hours for
my model. From what I've read on the BEPU/BEPS reports I can find the % of
the hours that the load is unmet, but is there a way to break this out into
cooling and heating time? The other alternative I see is to go through
either the SS-F reports, or the Air-Side HVAC section and add up all of the
zones unmet heating and cooling hours. Does anyone know of a better way to
determine this?

Thanks,

Michael Shields

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I like to look under Airside HVAC. Click on the summary tab, then click on "project" in the component tree on the left hand side. It will show you the sum automatically.

Kelsey Van Tassel

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When I look under the summary tab, it says I have 34% unmet hours. When
I look at the BEPS report, it says I have 3%. Does anyone know what the
difference in these numbers is?

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Maybe I am missing something, but when I click project the Project Totals
table does not show the sum of the hours, just a total percentage outside
throttling range which is the same as the BEPS/BEPU report, and does not
break it out by cooling/heating. Am I missing something?

Michael Shields

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It gives the total percentage of the project, but not the total hours.
It only breaks those out by system as far as I can tell.

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I guess you are right, it just shows the total percentage, but all of the systems do at least show up on one report. I was running a TRACE file so I couldn't double-check and I just remembered wrong, sorry.

Kelsey Van Tassel

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?the way the hours are counted. The Air-Side Summary report is good for showing heating vs. cooling hours, and which zones are problematic, but it counts hours simultaneously and yields an inflated number. Multiply the percentage in the BEPS report by the number of hours the fans are on and you?ll have the number you?re looking for. To split that total between heating and cooling, I apply the same ratio shown in the Air-Side Summary report. There?s probably a more accurate way to do it, but another user will have to enlighten all of us...

DAKOTA KELLEY

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Can't wait for version 3.64 which explicitly reports heating and cooling
hours in the BEPS report.

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Hi All,

I am working on filing out the LEED paperwork for submittal and for unmet
hours I am wondering does the reviewer want the total unmet load hours for
the building, or an average per zone? My building has about 100 zones, most
of which have 0 unmet hours, but I have one zone which has significant (more
than 50) unmet hours. Does this mean my model exceeds the requirement that
the difference between the baseline and the proposed be less than 50 hours?

Thanks for any advice.

Michael Shields

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Michael,

90.1's passage (G3.1.2.2) regarding unmet hours requirements is
something I had to re-read many times to get my head fully wrapped
around it... Here's my current interpretation:

1. You need to have 300 or fewer hours in each model.

2. The proposed is not allowed to perform worse than the baseline
by more than 50 unmet hours. If it does you have to make the baseline
"underperform" so they're within 50 of each other.

3. The baseline is permitted to perform worse than the proposed
(by any degree) as long as it's still 300 or fewer unmet hours.

You haven't said whether you're talking about your baseline or proposed
model, but the above points should guide you as to whether you need to
make an adjustment. Refer to G3.1.2.2 for review and further info.

~Nick

NICK CATON, E.I.T.

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Nick,

My baseline model currently has 0 unmet hours, and my proposed has around
100 total if I add up all of the unmet hours in all zones. From my
interpretation (and I believe you're confirming it) this does not qualify.
If I read 90.1 correctly then there is no weighting or averaging, it's just
a total unmet hours anywhere in the building (ie zone 1 hours +zone 2 hours
+zone 3 hours.. Etc). Does anyone else disagree with this interpretation?

Thanks,

Michael

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I put one small FYI at the end of Nick's #3 below, in all caps for the
sake of the plain text archives...

Dakota

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[For continuity, I'm attaching Michael's most recent response to
Dakota's followup... just some convulted copy/pasting to keep the
discussion moving in one direction]

Michael,

I'd like to caution you against a fairly common misinterpretation. 90.1
is unfortunately not crystal clear, but the general consensus on these
lists (including reviewer input) is that 90.1 is citing unmet hours as
"coincidental" unmet hours. The long and short of it is, you aren't
supposed to literally sum up the unmet heating and cooling hours of each
zone to come up with total unmet hours, even though it may seem
intuitive. If you do, you're likely unnecessarily penalizing one or
both models and putting extra work on yourself. See the message copied
below (scroll to the bottom and read-on-up) for a more in-depth
explanation/discussion of a "best practice" approach with eQuest -
there's more where that came from in the archives also.

~Nick

NICK CATON, E.I.T.

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Does anyone know if equest can model radiant ceilings (for heating and cooling)?

[cid:image002.jpg at 01CB2E29.E94B3CB0]

Adam McMillen, LEED AP BD+C

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Adam,

They cannot be modeled directly, nor credibly well indirectly. TRNSYS, EnergyPlus, IES and a few others are more appropriate tools for this. If you choose to not model the rest of the building in these programs, you could potentially (depending on system configuration) have the two software "communicate" loads/performance from one to another.

Regards,
Paul

Paul Erickson LEED(r) AP

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Michael

A thorough review of the documentation seems to have been undertaken in
2008. You should search the [Bldg-sim] archive (
http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/) for
this thread "Spam:Re: LEED NC Submittal Template, Heating/Cooling Hours
Loads Not Met".

I was very impressed with the thoroughness of Dan Russell's
contribution.

I think his analysis of the rules is correct - but I think that ASHRAE
would have better used the "worst space" as I think Carol Gardner has
suggested.

eQuest BEPS report unmet load percentage applies to "fan on" hours
(often less than 8760). In eQuest I find the system with the highest fan
hours in reports SS-R, total run hours, by changing the "component" to
review each system. Then I use the percentage from BEPS with the maximum
fan-on-hours to decide whether Appendix G criteria is fulfilled.

I would be happy to be corrected, but I think that there is no report in
eQuest that can identify the building concurrent unmet load hours
separated into heating and cooling as required for the LEED template.

Dan Coutin

Erdman Anthony

Troy, NY

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Hi Adam,

while these systems cannot be modeled explicitly in DOE2.2/eQuest, it can be
your attempt (as well others of us in similar shoes) to model something that
is thermodynamically representative of what your are trying to estimate.
For example could you get a VAV system to thermall act like a radiant
system? Yes, in some ways by 'turning down' the power consumed by the fans
because a radiant system doesn't consume fan energy with it's operation.
Although a VAV system wouldn't be your best choice, it indicates the way
you'll need to start thinking about how to get done what you are being asked
to do with the limitations you find yourself with.

In short, I'm learning on a project right now how to better represent active
chilled beams for my project. My approach thus far is to set up (1st) a
Dummy zone (i.e. very little floor area & zero loads) that I can attach a
DOAS System (selected as VAV in eQuest) too. This will give me my primary
ventilation air system that will "feed" ventilation air to my radiant system
conditioned zones. The radiant system (represented by a PIU system with
adjustments.) then has the command of "OA from: DOAS system" so that the
occupied zones are fed ventilation air and conditioned by the radiant
system.

This is the approach I'm using for this project. Is it right? Is it
wrong? Is there a better way?----It depends. I'm trying to make the best
choices based on what my project needs and what information/support I have
found from others. I also suggest doing a search for 'radiant systems' on
the www.onebuilding.org archives for eQuest & Bldg-Sim at the least. You
should find more info on which direction/approaches are being applied by
others.

In the end, if you have applied sound engineering theory & fundamentals, and
have reviewed, double & triple checked your results against reference data,
and then you still stand behind your numbers, you should feel that you have
developed a pretty solid model (representation) of your project design. And
that's the best we can do, until we have the opportunity to M&V the building
after design and verify the validity of our estimatations post-occupancy.
Has anyone else had the opportunity to put thier energy model results to the
test, post-occupancy?

pasha

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I should know this one, but draw a blank.

The Wizard asks if you want Standard, Hi Efficiency, or Premium Efficiency
motors for your fan system.

How do those show up in the .INP file? That will give me a clue as to what
Parameters to modify for changing to PE motors.

Thanks.

John R. Aulbach, PE, CEM

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John,

In the INP, it is the "MOTOR-CLASS" input. You see in the INP something like:

FLOW = 300
NUMBER = 1
HEAD = 80
MECH-EFF = 0.776
MOTOR-CLASS = HI-EFF
CAP-CTRL = ONE-SPEED-PUMP

_____________
Demba NDIAYE

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Thank you, Demba.

But this is for a PUMP. Not a FAN.

John

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I account for motor eff by changing the total eff, where total eff = motor eff * mech eff. I believe the keyword for total eff in the inp file is SUPPLY-EFF for supply fans.

___________________________________________

Jeremy McClanathan, LEED? AP

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Thank you, Jeremy. By "plug and chug", that seemed to be the Parameter that
changed in running a test building through Standard, High, and Premium
Efficiency.

Wouldn't it be nice if some of this stuff was discussed more in the Manuals ??

John

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Sorry John,

Did not realize you are talking about fans. When I saw Motor Class, my mind immediately jumped to pump because that is the only place where eQuest allows to input it.

Yeah, for fans, as Jeremy pointed out, you have two keywords in eQuest: SUPPLY-EFF and MECH-SUPPLY-EFF. The first is the combined efficiency (fan + motor) and the second is the mechanical efficiency of the fan alone.

_____________
Demba NDIAYE

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Not entirely on topic but what is a typical fan
coil motor efficiency? I have been using 25%.

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Chris:

These are fractional HP motors. Small motors used to be 84%, but with Electrical
commutating motors,?I have no idea.

John R. Aulbach, PE, CEM

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Shaded pole motors are typically around 20% efficiency; PSC typically 50%-65% efficiency. ECM motors average are around 75% efficiency.

Mike Andelman

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It's time to do that thing again where we talk about unmet hours. I'll give a little 

background first: I'm new to equest and to the HVAC industry, so bear with me. The project is a big manufactures about (861112.8 foot2), split into 12 zones and predominantly served by series VAV terminals using chilled water. It's in Guanajuato,MX so and are no economizers. I've spent the majority of the past few days reading previous discussions and trying a variety of changes. I have attached the INP and PD2 for convenience.

I initially tried to represent the system based on the mechanical/electrical schedules, but that yielded many unmet hours (99%), so it is currently set to auto-size, but am still at about 600 unmet hours (7%). 7 of the zones are series VAV, 2 are single-zone with reheat, and one is a packaged single zone for the MDF room.

* Changing to an auto-sized system provided a large reduction in UH.

* I changed from 4°R to 8°R throttling range. It´s normal but How do I Know, until what number is good or bad? 

* am trying to not manipulate the data by adjusting the cooling/heating ratio.

* The setpoints are 74c/70h. I tried changing them a few degrees in either direction, but did not get a large enough reduction.

* have the fans cycling at night (no OA), which did help reduce the hours

* switched into DDE and set actual CFM from the mechanical plans. This resulted in an increase

. I think my inexperience hampers my ability to troubleshoot some of the problems because I don't necessarily have a good sense for what a reasonable result/prediction is.

I appreciate any assistance on this matter and am open to suggestions as far as proper modeling techniques and troubleshooting methods.

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