[Equest-users] Baseline Airflow Autosizing

[Joshua Wolfe]

Christina,

I always just solve the equation in AHSRAE 90.1 for kW/cfm and input directly into eQuest. The Delta T box you are referring to, is the increase in temperature of the airflow due to motor heat at design conditions I leave default in baseline case(2-4F usually). I always let the program autosize in the baseline case 1.00 for system, 1.15 for cooling and 1.25 for heating. I then look at SV-A reports to get maximum heat extraction rate of the equipment and calculate my dt's (1.08*cfm*dt) which I then adjust airflows for each zone to match the 20F found in ASHRAE 90.1. I have not found a way to directly input design delta T (20F per ASHRAE) of zones to calculate airflow. Maybe someone else can knows a better way and will answer this post.  Hope that helps some.

Josh
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Christina Galyfianaki
Sent: Monday, October 26, 2009 10:50 AM
To: Matutinovic, Luka; reniel barroso; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Baseline Airflow Autosizing

Hello everybody

I use the auto-sizing option as Luca described and I trusted that the when specifying the Sizing Ratio to be 1.15 for cooling and 1.25 for heating would give me the equipment capacity as required by G3.1.2.2.
I then run the baseline for the first time just to get the supply airflows (cfm) from the SV-A Report. Then I used this value to find the fan Brake Horse power from Table G3.1.2.9 and then calculated the Pfan from the formula G3.1.2.9
Then I find the fraction of fan power per flow Rate in kW/cfm and input this value with a DT of 19.8 (as per G3.1.2.8)

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It seemed to work fine and the USGBC accepted the model. I am really interested to double-check with other modellers methodology.
But mostly I want to ask the following Question:

Do you use the auto-sizing method for the Proposed building?

You can still input the actual Sizing ratio, DT and kW/cfm of your design that will determine your energy consumption and thus reflect your design principles. I will appreciate the feedback of the experienced users.

Kind Regards,
Christina




Christina Galyfianaki
Simulation Consultant

Building Physics Division



LCEA CIBSE Accredited, EPCs levels 3/4/5



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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Matutinovic, Luka
Sent: 26 October 2009 13:33
To: reniel barroso; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Baseline Airflow Autosizing

Reniel,

Are you referring to the sizing runs from G3.1.2.2.1?  If so, leave the design cfm on each air-handler blank (see screenshot below) and eQuest will size the flows based on the sizing option you've specified (Click on a system, go the Basics tab, and see "Sizing Option").

If you need to size the baseline equipment capacity as per G3.1.2.2, then multiply the auto-sized flows from the first step, by 1.25 for heating and 1.15 for cooling and enter the result as the design cfm.

I think you might be able to do the second step directly by specifying a sizing ratio (see second screenshot), although for whatever reason I haven't done it this way in the past, so I'd be curious to hear from the more experience eQuesters what approach they take.

Hope the helps,

Luka Matutinovic, B.A.Sc., LEED(r) AP
Green Building Consultant

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________________________________
From: reniel barroso [mailto:renielbarroso at yahoo.com]
Sent: Sunday, October 25, 2009 1:37 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Baseline Airflow Autosizing

I've been trying to look on the equest interface where we can set the airflow to autosize itself as per LEED baseline requirement.
I don't think we have this option here. Have we?

Thanks in advance.

Reniel



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