[Bldg-sim] Ashrae 90.1 - Unmet hours

Deepak Agrawal deepak0agrawal at gmail.com
Tue Oct 27 00:37:24 PDT 2009


dear All...

the entire issue with unmet hours has been analysed on my website, on this
link

http://greenbuildinggenie.com/tips/leed-issues/item/15-understanding-total-number-of-unmet-hours-as-per-ashrae-901-

regards

On Tue, Oct 27, 2009 at 10:46 AM, ashu gupta <kce2 at kamalcogentenergy.com>wrote:

>  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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-- 
Deepak Agrawal
Hyderabad, India
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