[Bldg-sim] Ashrae 90.1 - Unmet hours

[surekha tetali]

I have done a small experiment; I created a block model and simulated it on
auto sizing.
There were no unmet hours in this case. Hence,I manually decreased the
supply cfm (flow/area) in the zone which started increasing the unmet hours.
The % of unmet was varying as a % of number of hours HVAC fan is ON.The cfm
was decreased till the unmet hours were 100% (cooling unmet). In this case
the total number of unmet hours of the building are similar to the total
number of hours the system fan is ON. I changed the cooling setpoint
temperature when the system fan is OFF and this had shown no effect on unmet
hours.

These percentage unmet hours (in Visual DOE)  hence seem to be the %  of the
total number of hours the HVAC fan is ON.



Surekha Tetali
Building Science Research Centre
IIIT Hyderabad.


On Tue, Oct 27, 2009 at 8:54 PM, Rosenberg, Michael I <
michael.rosenberg at pnl.gov> wrote:

>  Ashu,
>
>
>
> I am in agreement with everything you stated except possibly this;
>
>
>
> “When percentage of unmet is specified, than this is the percentage of
> total number of hours (1 year- 8760 hours) for which the simulation is
> performed (not just the occupied hours)”
>
>
>
> My understanding is that some simulation programs (DOE2 and eQuest in
> particular) report this as a percentage of hours that the fan is running. I
> could be wrong, and I am sure some of you DOE2 experts can comment on what
> is reported in the DOE2 BEPS report.
>
>
>
> Mike
>
>
>
>
>
> *__________________________*
>
> *Michael Rosenberg*
> Senior Commercial Buildings Energy Analyst
> ENERGY & ENVIRONMENT DIRECTORATE
>
> Pacific Northwest National Laboratory
> 2032 Todd Street
> Eugene, OR 97405
> (541) 844-1960
> michael.rosenberg at pnl.gov
> www.pnl.gov
>
> *From:* ashu gupta [mailto:kce2 at kamalcogentenergy.com]
> *Sent:* Monday, October 26, 2009 10:17 PM
> *To:* Rosenberg, Michael I; 'Nick Caton'; 'Crockett, Jim'; 'Kendra Tupper'
>
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* RE: [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> Dear All,
>
>
>
> Explanation of Unmet Hours is as follows:
>
>
>
> *Unmet Hours:*
>
> Unmet hours of a building are the summation of the number of hours when the
> heating or the cooling set point temperature of a zone is not met either by
> the HVAC system or by the plant.
>
> *Understanding/Interpreting/Calculating the number of unmet hours:*
>
>    - Unmet hour is for a particular zone when the zone indoor temperature
>    is higher than the heating or cooling set point specified in that hour.
>    - The number or the percentage of unmet hours in a building is usually
>    given as one of the outputs of the simulation.
>    - Zone wise unmet can also be read from the various output files
>    provided by the software used for simulation.
>
> (Example:
>
> Visual DOE: “SS-J System Peak Heating and Cooling Days” report &
>
> Energy Plus: Output Variable, “Time Cooling Set point Not met”)
>
>    - When two zones are unmet at the same hour, this will count to one
>    unmet hour for the building.
>    - When two zones have unmet hours during different non overlapping
>    times of a day, the total number of unmet hours in that day is the summation
>    of these unmet hours of each zone. This total for the year should be
>    considered as the total unmet hours of the building.
>
> *Example: *
>
> When each zone is unmet in the specified hours as beside,
>
>
>
> Zone 1 unmet during:                        6          8          14
> 16
>
> Zone 2 unmet during:                        6          8          12
> 16
>
> Zone 3 unmet during:                        7          8          12
> 13
>
>
>
> Total number of unmet hours of the building: *7 hrs* and not 12hrs.
>
> 6          7          8          12        13        14        16
>
>
>
>    - When percentage of unmet is specified, than this is the percentage of
>    total number of hours (1 year- 8760 hours) for which the simulation is
>    performed (not just the occupied hours)
>    - As per ASHRAE 90.1-2004, the unmet hours of the total building should
>    be less than or equal to 300 hours and the difference in the base case and
>    proposed case should be less than or equal to 50 hours.
>    - If unmet load hours in the proposed building exceed the unmet load
>    hours in the baseline building by more than 50, then the size of equipment
>    in the baseline building shall be reduced incrementally, until the condition
>    is satisfied.
>
>
>
>
>
> Thanks
>
> Ashu Gupta,
> Project Engineer,
> Kamal Cogent Energy,
> Kamal Ratan Chanbers 1st Floor,
> Opp. GPO, M.I. Road,
> Jaipur 302001
> Ph 141 2373185(W)
> Ph 9251665008(M)
> kce2 at kamalcogentenergy.com
> www.kamalcogentenergy.com
>   ------------------------------
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Rosenberg, Michael
> I
> *Sent:* Tuesday, October 27, 2009 9:07 AM
> *To:* Nick Caton; Crockett, Jim; Kendra Tupper
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> I think eQuest and any DOE2 based software does report the hours of loads
> not being met as required by Appendix G. In the BEPS report it gives
> “PERCENT OF HOURS ANY SYSTEM ZONE OUTSIDE OF THROTTLING RANGE”. My
> understanding of this number is that it is a percentage of scheduled fan
> run-time hours, so some calculation may be necessary.
>
>
>
> *__________________________*
>
> *Michael Rosenberg*
> Senior Commercial Buildings Energy Analyst
> ENERGY & ENVIRONMENT DIRECTORATE
>
> Pacific Northwest National Laboratory
> 2032 Todd Street
> Eugene, OR 97405
> (541) 844-1960
> michael.rosenberg at pnl.gov
> www.pnl.gov
>
> *From:* Nick Caton [mailto:ncaton at smithboucher.com]
> *Sent:* Monday, October 26, 2009 8:20 PM
> *To:* Rosenberg, Michael I; Crockett, Jim; Kendra Tupper
> *Cc:* bldg-sim at lists.onebuilding.org
> *Subject:* RE: [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> Mike,
>
>
>
> I appreciate you bringing this up.  This definition drives straight to the
> heart of defining the issue-at-hand…  Since I kinda presented both sides of
> the issue at once – I’d like to clarify where I stand regarding what the
> correct interpretation *should be*.
>
>
>
> The logic is as follows:  If a modeled year has 8,760 hours, can there be
> 10,000 unmet load hours?  By strict reading of the standard’s definition
> below, I would put my foot down stating there can *only* be 8,760, at
> most.
>
>
>
> By common practice however, it appears a majority (myself included) sum
> unmet cooling/heating hours between the zones, even if they should fall on
> the same modeled hour, against the intent of the standard.
>
>
>
> My pure speculation (for what it’s worth, as a young EIT) is this practice
> developed because eQuest BDL reports don’t present the crunched numbers in a
> way that makes the sum of unmet load hours, as intended by 90.1, easy to
> determine.  I wouldn’t be shocked to learn other energy modeling software
> packages generate LEED compliance summaries featuring unmet load hour totals
> in sync with the real intent of ASHRAE 90.1.
>
>
>
> If there’s anything I’ve learned from going out on a limb, it’s that I’m
> sure to learn something whether I fall or not!
>
>
>
> ~Nick
>
>
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> *Check out our new web-site @ *www.smithboucher.com* *
>
>
>
> *From:* Rosenberg, Michael I [mailto:michael.rosenberg at pnl.gov]
> *Sent:* Monday, October 26, 2009 7:39 PM
> *To:* Nick Caton; Crockett, Jim; bldg-sim at lists.onebuilding.org
> *Subject:* RE: [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> Nick,
>
>
>
> Your interpretation is the correct one. According to the definitions in
> Standard 90.1.
>
> *unmet load hour:* an hour in which one or more zones is outside of the
> thermostat setpoint range.
>
>
>
>
>
> Mike
>
> *__________________________*
>
> *Michael Rosenberg*
> Senior Commercial Buildings Energy Analyst
> ENERGY & ENVIRONMENT DIRECTORATE
>
> Pacific Northwest National Laboratory
> 2032 Todd Street
> Eugene, OR 97405
> (541) 844-1960
> michael.rosenberg at pnl.gov
> www.pnl.gov
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Nick Caton
> *Sent:* Monday, October 26, 2009 5:33 PM
> *To:* Crockett, Jim; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> Jim,
>
>
>
> That’s actually a really good question that I was afraid to ask when I
> first encountered it – kudos to you!  I’ve currently resolved to follow what
> others seemed to be doing within and outside of my office:  Sum up all unmet
> hours for cooling and heating between the zones just as you describe.   In
> your example, I’d agree that the unmet hours of your 301 zone building total
> 301.
>
>
>
> I do agree that this doesn’t seem intuitively to be the intent of the
> standard, however between what is suggested within 90.1, the LEED handbook,
> and the LEED credit templates – I honestly can’t see any clear indication
> either way on which is the appropriate interpretation.
>
>
>
> I think the appropriate metric for ensuring appropriately sized systems
> should be something like: “hours of the modeled year in which at least one
> zone has an unmet cooling/heating load,”  but I think that was avoided by
> all concerned parties because it’s too wordy!
>
>
>
> My acting interpretation, again referencing your example, is that all
> systems of your 301 zone example affecting the zones with unmet
> cooling/heating hours should have their heating/cooling/overall sizing
> capacity ratios increased incrementally until the design hours fall below
> 300 (and/or within 50 of the sum from the other model, depending on your
> situation).
>
>
>
> Afraid I’m only really adding to the discussion here without providing a
> solid answer.  Would like to echo the desire to see anyone’s experiences
> that would help us know the “right” way to interpret this (in my case,
> specifically in the context of a LEED submittal).
>
>
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> *Check out our new web-site @ *www.smithboucher.com* *
>
>
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [mailto:
> bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Crockett, Jim
> *Sent:* Monday, October 26, 2009 4:27 PM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Ashrae 90.1 - Unmet hours
>
>
>
> Ashrae 90.1 (2004) Appendix G3.1.2.2 requires a baseline building to have
> less than 300 unmet hours.  What exactly does this mean?
>
>
>
> To illustrate my question:  assume you have a building with 301 zones, and
> each zone has 1 unmet hour per year.  This gives you a total of 301 unmet
> hours, and requires you to increase your baseline equipment capacity.  But
> you could argue that, on average, the building has only 1 unmet hour per
> year.
>
>
>
> Have any of you run into this?  Is it addressed in an addendum somewhere,
> etc?
>
>
>
> Any help is appreciated.  Thanks,
>
>
>
>
>
>
>
> Jim Crockett, P.E.
>
>
>
> Senior Project Engineer
>
> Energy & Carbon Management
>
> Nexant, Inc.
>
> 4021 S. 700 E., Suite 250
>
> Salt Lake City, Utah 84107
>
>
>
> (801) 639-5603 - phone
>
> (801) 266-4786 - fax
>
>
>
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