[Equest-users] Assign 2 systems to the same zone

Sun Jul 12 03:36:28 PDT 2020

Hi Nicholas,

Thanks much for your valuable response! I will be looking into your
possible solutions, however I tried point #3 myself before just to check
the possibilities and have found that it  could be problematic, especially
if you have multiple other systems also to be added to the same zone. It’s
a tedious task.

Regards,

Tanya

*From:* Nicholas Caton [mailto:Nicholas.Caton at se.com]
*Sent:* 07 July 2020 16:49
*To:* Tanya Soji <tanya.soji at quantumesco.com>
*Cc:* equest-users at lists.onebuilding.org
*Subject:* RE: [Equest-users] Assign 2 systems to the same zone

Hi Tanya!

There is a long-standing limitation with doe2/eQuest in not permitting more
than one system per zone, however in recent years, this rule has been
relaxed a bit.

If you treat your AHU as a DOAS system (responsible for delivering
ventilation air), then you can have a DOAS + another system technically
servicing the same zone.  This does require building your model using the
doe2.3 engine.

If a DOAS circumstantially will not work however, and you wish to model 2
or more systems servicing the same zone, there remains a couple
long-standing “workarounds” I’ve seen promoted in this community:

   1. The targeted zone can be split into 2 or more air-wall sharing
   spaces, geometrically considering where the thermostats for the various
   systems actually lie and (if skin loads are in play) which system is
   intended to handle specific space loads. Changing up model geometries is
   totally possible, but can be a more involved proposition post-wizards.  I
   recommend newer energy modelers to move back to wizards if they aren’t too
   far past the line of detailed mode edits.
   2. The presence of a second system can sometimes be approximated through
   cleverly tweaking one system and adding zonal baseboards or zonal
   heating/cooling coils, if applicable.  This can require sacrificing some
   degree of capacity for independent system operation, but in some cases is a
   totally fair representation in terms of model accuracy.
   3. I’ve seen a couple cases where the modeler chose to duplicate the
   associated space/zone, assign its internal loads (like lights/ plug loads)
   to “ghost” meters (to prevent double counting those energies), then assign
   a second system to the duplicated zone.  This can be problematic relative
   to the other options presented, in that you’re missing any opportunity to
   capture the interactivity between the systems.  In some cases however, you
   might not want to model interactivity… just consider that one systems’
   controlling thermostat may be affected by space heating/conditioning
   performed “by others.”

I hope this is helpful!

~Nick

*Nick Caton, P.E., BEMP*

  Senior Energy Engineer

  Energy and Sustainability Services
  Energy Performance Contracting

D
M
E

913 . 564 . 6361

785 . 410 . 3317

*nicholas.caton at se.com <nicholas.caton at se.com>*

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219

*From:* Equest-users <equest-users-bounces at lists.onebuilding.org> *On
Behalf Of *Tanya Soji via Equest-users
*Sent:* Tuesday, July 7, 2020 6:30 AM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] Assign 2 systems to the same zone

[External email: Use caution with links and attachments]
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Hi everyone,

I just wanted a small clarification on the Air-side HVAC systems.

How does  eQuest go about assigning two different HVAC systems (AHUs &
Package units in my case) to the same zone??

It does not let me add the same zones to the second system (Package units).

Regards,

Tanya

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