[Equest-users] Modelling thermal zone with multiple AHUs

Julien Marrec julien.marrec at gmail.com
Thu Mar 5 01:13:28 PST 2015


Anura,

Nick is spot on... It's always a pickle to go one way or another between
short term gain and potential further problems.

One suggestion if you want to do it with individual AHUs...
Create one of them that will serve as your "master". For the rest of them,
use the "LIKE" keyword. This way you'll have to change only one of them if
you need to adjust a parameter, and it will propagate to the rest.


Best,
Julien


--
Julien Marrec, EBCP, BPI MFBA
Energy&Sustainability Engineer
T: +33 6 95 14 42 13

LinkedIn (en) : www.linkedin.com/in/julienmarrec
LinkedIn (fr) : www.linkedin.com/in/julienmarrec/fr
<http://www.linkedin.com/in/julienmarrec>

2015-03-05 7:48 GMT+01:00 Nicholas Caton <ncaton at catonenergy.com>:

> Hi Anura,
>
>
>
> If the individual systems do not act independently, or otherwise are not
> expected to handle substantially different load profiles through the year
> (consider beyond internal loads: do some zones have differing skin loads?),
> then it’s probably safe to combine systems.
>
>
>
> In my experience, I would however caution this particular approach of
> combining systems to streamline your model development has potential to
> backfire.  The time you save in the short term with inputs could be lost to
> processing those system inputs (creating & documenting those
> heating/cooling/airflow capacity sums and weighting associated unitary
> efficiencies) and perhaps also in troubleshooting/re-constructing the model
> if you find out later the assumption of identical system behavior was
> off-base.  On the other hand, the extra time you would spend setting up
> each individual system could be better invested elsewhere in the modeling
> process to create a better final product (or towards getting home on time)!
>
>
>
> In my mind, this sort of “how detailed is necessary” decision is a matter
> of risk:reward.  It’s a regular category of judgments that pop up all the
> time in new work.  Being able to recognize and explore opportunities for
> acceptable approximations is a defining trait for experienced modelers.
>
>
>
> Insofar as LEED reviewers are concerned, I have anecdotally combined
> systems (documenting them as such with supplemental language) without
> incident in past projects.
>
>
>
> Kind regards,
>
>
>
> ~Nick
>
>
>
> *NICK CATON, P.E.*
> *Owner*
>
>
>
> *Caton Energy Consulting*
>   1150 N. 192nd St., #4-202
>
>   Shoreline, WA 98133
>   office:  785.410.3317
>
> www.catonenergy.com
>
>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *Anura Perera
> *Sent:* Wednesday, March 04, 2015 4:01 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Modelling thermal zone with multiple AHUs
>
>
>
> Dear All,
>
>
>
> I am modelling a building having thermal blocks with multiple thermal
> zones. Each thermal zone has an AHU. The floor level internal loads are
> evenly distributed. As such I am planning to model the thermal block
> considering all AHUs in the thermal block as lumped into one large AHU with
> total capacity of all individual AHUs of zones in the block.
>
>
>
> Will this be an acceptable approach for LEED reviewers?
>
>
>
> Any experience to share please?
>
>
>
> Thanks in advance
>
> Anura
>
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