[Equest-users] Question about Indoor Temperature

[Nicholas Caton]

Each time you simulate your model, the cooling needs for a given zone are calculated twice.

First, during the LOADS portion of the simulation:

  *   The zonal inputs DESIGN-COOL-TEMP and DESIGN-HEAT-TEMP are used to estimate the “steady-state” exterior skin loads and intra-zonal loads between walls/floors/ceilings.  When I say “steady-state” I’m describing one or (typically, from wizard-bourne models) a series of calculations for load design conditions defined by your DESIGN-DAY inputs, as occurring.
  *   If you ever learned to do load calcs by hand/spreadsheet to determine loads present on a system before considering ventilation… this first part of the simulation is pretty analogous to getting that far.
  *   These loads are used to help auto-size any systems for which you didn’t provide manual inputs for the heating/cooling/airflow capacity…
  *   Note that all of the SIM reports starting with “L” are reporting on loads determined during this first LOADS portion of the simulation
Then, during the SYSTEMS portion of the simulation takes over.  From here, the hourly (8760) simulation occurs that among others things, distinctly moves to

  1.  Consider heat transfer hour over hour (and the effects of thermal mass)
  2.  Consider the effects of SYSTEMS conditioning as well to determine the actual zone temperature each hour (now varying vs the “steady state” inputs used during the LOADS portion of the simulation)
  3.  Layer in the effects of ventilation loads (including natural/window ventilation)
  4.  DESIGN-COOL-TEMP and DESIGN-HEAT-TEMP are no longer used to assert or otherwise “bound/control” zone temperatures.  During this portion of the simulation, zone temperature is calculated independently, and the thermostat inputs/schedules (or lack thereof) are the primary means of defining system heating/cooling behavior.


There’s a lot more discussion in the mailing list archives if you are interested in further reading, but I’m hopeful this helps you understand better the contribution of those zonal DESIGN temp inputs in the scheme of things.


~Nick

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Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Energy and Sustainability Services
  Energy Performance Contracting
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785 . 410 . 3317
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Konstantina Kalliakoudi via Equest-users
Sent: Tuesday, April 21, 2020 7:01 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Question about Indoor Temperature


[External email: Use caution with links and attachments]

________________________________


Hello to all equest users,
I have following question.
At e-quest I give the specific Indoor Temperature
via Cool Design Temperature = 75 F
and Heating design Temperature = 70 F (for example)

In my building I have such a load from people that during the Winter (the heating period) I need cooling energy.

My question is how is this cooling energy calculated?

Based on which indoor temperature? The 70F or the 75F?

Thank you very much
Konstantina Kalliakoudi
Mechanical Engineer M.Sc.

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