[Equest-users] eQuest Sizing Methodology

[Chris Hadlock]

Fellow eQuesters,

I'm looking to better understand how eQuest is using my sizing inputs to
auto-size the heating & cooling capacities as well as airflows. In my
example below (for a MURB in Canada), I'm modeling a PSZ system with DX
cooling and HW heating. I've shown in the images below the (first image)
sizing inputs from the Basics tab, the (second image) sizing inputs on the
heating tab and (third image) the sizing outputs from the SV-C report. For
this example, all of the values have been auto-sized based on the sizing
inputs (and in case it matters, this system has no ventilation load):
[image: image.png]         [image: image.png]            [image: image.png]

I'm looking to better understand how eQuest takes all of my inputs (and
which inputs specifically) and derives cooling capacity, heating capacity
and airflow for my system in question.

Looking at the SV-C report and the highlight Cooling values:

   - How does eQuest derive the 232 cfm value (Design Day Peak airflow)?
   - How is the 6.97 MBH capacity derived? I'm assuming this is based on
   load passed onto the system, but there are clearly other system-related
   inputs that affect this value.
   - I believe the 331 cfm airflow shown as the Design Capacity Airflow is
   calculated based on my specified Rated Flow/Capacity value (7.11 MBH / 12
   MBH/Ton * 558 cfm/Ton = 331 cfm)

Looking at the Heating values in the SV-C:

   - How is the -8.66 MBH capacity derived? I'm assuming this is based on
   load passed onto the system, but there are clearly other system-related
   inputs that affect this value?
   - I believe the -13.49 MBH is calculated based on 331 cfm and a heating
   dT of 37.8F (331 * 37.8 * 1.085 = -13575) (I might be a little off with my
   constant value of 1.085). Does eQuest use the Heat dT specifid on the Basic
   tab or the HT-COIL-AIR-DT value I specified on the Heating Coil Cap tab?

I would like to better understand how eQuest uses the "Heat Sup/Ret dT" and
the "Cool Sup/Ret dT" inputs for these calculations?  To further understand
these interactions, I've run two scenarios.

Scenario 1: if I reduce the Heat dT to 21F and leave the Cooling dT as
19.8F, I get the following output. Why does changing the Heating dT affect
the cooling capacities? And how is the Design Heating Capacity of -15.53
MBH determined?

[image: image.png]

Scenario 2: if I reduce the Cool dT to 10F and leave the Heating dT as
37.8F, I get the following output.

[image: image.png]

Any insights that would help me make sense of the eQuest sizing methodology
would be appreciated.

Chris
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