[Equest-users] eQuest Sizing Methodology

[Chris Hadlock]

To clarify one point - I'm using eQuest 3.65 7175 DOE2.3 in my question
below.

On Wed, Sep 11, 2024 at 3:06 PM Chris Hadlock <cjhadlock at gmail.com> wrote:

> 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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