[Equest-users] eQuest Sizing Methodology

[Bill Bishop]

Hi Chris,

Doug Maddox worked on DOE2.3. Have you checked out his YouTube video on HVAC sizing? Douglas Maddox eQUEST DOE23 HVAC Sizing<https://www.youtube.com/watch?v=-w-nhJgjXZw>

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP
Senior Associate / Sustainability & Energy Engineer of Distinction
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Chris Hadlock via Equest-users
Sent: Thursday, September 12, 2024 8:50 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] eQuest Sizing Methodology

External Email: Treat links and attachments with caution.
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<mailto: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):
         [cid:image001.png at 01DB04F3.30D39BE0]

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?

[cid:image002.png at 01DB04F3.30D39BE0]

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

[cid:image003.png at 01DB04F3.30D39BE0]

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

Chris

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