[Bldg-sim] Problems with Design Days

Matt Edwards Matt.Edwards at me-engineers.com
Tue Sep 18 15:06:45 PDT 2012


Thanks Rut.  I only have two "design day" components in the model.  The trouble is with how many days you allow them to run for.  It's the bottom field on the lower left hand side of the design day dialogue box with BDL keyword NUMBER-OF-DAYS.  The simulation behaves very oddly when you modulate this number, and to this point my conclusion is there is trouble within eQUEST with accurately allotting airflow to zones as required based on their "design day" calculated load.  I haven't figured out exactly what the problem is.  The building in question has an odd footprint shape with lots of glass, so I'm betting the problem is with how eQUEST calculates solar load and provides for zone airflow in response.

My issue with the way LEED unmet hours are reported/reviewed is that the fields in BEPS/BEPU do not provide any information troubleshoot them.  In previous versions of eQUEST (DOE-2.2-47d and before) there were no heating and cooling fields, so you either had to use the PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE which didn't break them up into heating and cooling or use the SS-R reports.

I often find under eQUEST v3.64 that the SS-R reports show no unmet hours anywhere, but there are still some showing up in the BEPS/BEPU reports under HOURS ANY ZONE ABOVE COOLING THROTTLING RANGE and HOURS ANY ZONE BELOW HEATING THROTTLING RANGE.  I'm suspicious of them since during the same run the PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE lists 0 or a very small percentage (0.05% or lower).  How can the two not agree?

As far as my comments, apologies if you're a LEED reviewer.  If you are, you have a tough job, and there is a lot of information to pour over to determine if a model is done correctly.  Appendix G is still very ambiguous since it grew out of the pre-LEED days and is meant to appease many software packages.  It would be nice to have more specific information about how passages in Appendix G are interpreted, and perhaps a revamp would be appropriate since the energy modeling world has gone through seismic change in the last 5 years.

Thanks for the response.

Matt Edwards, P.E., LEED AP BD+C
mechanical engineer

M-E Engineers, Inc.<http://www.me-engineers.com/>
10055 west 43rd avenue
wheat ridge, co 80033

office:  303.421.6655
direct:  720.898.3164
matt.edwards at me-engineers.com<mailto:matt.edwards at me-engineers.com>

The information transmitted is intended only for the person or entity to which it is addressed and contains information confidential and proprietary to M-E Engineers, Inc. and its affiliates.  Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is strictly prohibited.  If you received this in error, please contact the sender and delete the material immediately.

From: Rut Wattanasak [mailto:rwattanasak at emoenergy.com]
Sent: Tuesday, September 18, 2012 3:46 PM
To: Matt Edwards
Subject: RE: Problems with Design Days

Hi Matt,

You shouldn't have more than two "design days" defined under eQUEST's 'Project&Site' tab ; one CDD and one HDD with the design temperatures based on ASHRAE 90.1 Table D-1 or similar deign day data source.  I'm looking at my model and I couldn't even add another design day, beyond the two I've already had.

I've run into some issue with the mystery unmet hours before.  It's most likely stemmed from a 'single-zone-controlled' system with multiple thermostat schedules, such as PSZs and SZRs will only allowed one thermostat'ed zone per system.

Additionally, have you made any adjustments to the internal loads for the zones with the unmet hours?  By adjusting the internal loads, it should help the HVAC system size proper air flow into those zones.

LEED reviewers have always looked at these unmet load hours...not sure what the last comment is about, because Appendix G dictates that you may not exceed the total of 300 hours combined.  By not conforming to the requirement, it is seen as your models are not properly created.  Since you mentioned LEED reviewer, did the model come back from LEED comments for clarification, or you're just being cautious.  For the latter, good for you.  If it's because of the former, I'd suggest having someone with LEED modeling experience take a look at the models along with the LEED comments/questions.

I hope some of this helps.  Good luck.

Rut Wattanasak
LEED AP BD+C
Energy Engineer
EMO Energy Solutions
3141 Fairview Park Dr, Suite 450
Falls Church, VA 22042
703-205-2445

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org]<mailto:[mailto:bldg-sim-bounces at lists.onebuilding.org]> On Behalf Of Matt Edwards
Sent: Tuesday, September 18, 2012 5:18 PM
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] Problems with Design Days

Hello all,

Has anyone had trouble with erroneous "HOURS ANY ZONE ABOVE COOLING THROTTLING RANGE" when using cooling design days?  This number reported in both the BEPS and BEPU reports does not offer any insight on where it comes from, so it's especially difficult to troubleshoot.

I'm noticing several different simulation runs where the "PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE" is at either 0 or 0.01% while there are thousands of "HOURS ANY ZONE ABOVE COOLING THROTTLING RANGE."  I thought when this field was added that it was supposed to report unmet hours, but I can't see why the numbers don't agree.

It appears that eQUEST has a hard time distributing airflow to zones correctly unless enough days are included in the "design day" dialogue box, but when you enter too many, the phenomenon above tends to occur.

Can anyone shed light on where the "HOURS ANY ZONE ABOVE COOLING THROTTLING RANGE" and "HOURS ANY ZONE BELOW HEATING THROTTLING RANGE" come from since LEED reviewers are now looking at this and only this to determine unmet hour compliance?

Thanks,

Matt Edwards, P.E., LEED AP BD+C
mechanical engineer

M-E Engineers, Inc.<http://www.me-engineers.com/>
10055 west 43rd avenue
wheat ridge, co 80033

office:  303.421.6655
direct:  720.898.3164
matt.edwards at me-engineers.com<mailto:matt.edwards at me-engineers.com>

The information transmitted is intended only for the person or entity to which it is addressed and contains information confidential and proprietary to M-E Engineers, Inc. and its affiliates.  Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon this information by persons or entities other than the intended recipient is strictly prohibited.  If you received this in error, please contact the sender and delete the material immediately.

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