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

[Nicholas Caton]

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

[cid:image001.jpg at 01D65433.20CDC5B0]
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<mailto:nicholas.caton at se.com>
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219

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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


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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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