[Equest-users] How detailed is necessary

[Jones, Christopher]

Nick’s comment brings up a question.  I am interested in others’ opinions on “how detailed is necessary” in reference to combining spaces.  I tend to combine spaces to reduce the number of zones in the model.  For example, I will combine a group of interior offices with adjacent washrooms, storage rooms, and other service spaces with exhaust only.  I know others will define each of these spaces individually significantly increasing the number of spaces/zones in the model.

The benefit of combining spaces is to reduce the time it takes to draw the spaces in eQuest.  This helps to reduce the complexity of the model and the run time.
The drawback is that you have to sum the lighting, process loads, and HVAC inputs, etc.  I use pivot tables to do the summing for me.

Any thoughts appreciated.

Christopher Jones, P.Eng.
Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nicholas Caton
Sent: Thursday, March 05, 2015 1:48 AM
To: Anura Perera; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modelling thermal zone with multiple AHUs

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<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<mailto: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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