[Equest-users] Dual Duct with package Cooling

Tue Jun 14 16:25:10 PDT 2022

It is - this is a multizone system with hot deck and cold deck where it blends the two airflows to satisfy the zones, taking constant flow overall with proportion of cold and hot deck air. The mixing takes place at the AHU though and a single duct goes out to the zone as opposed to the dual-duct approach. The size of the units is limited since there isn't enough room for ductwork branches, I've usually seen these from three to seven zones. So in that regard it makes sense for a DX although I've mostly seen these in university buildings which do have CHW and HW or steam, sometimes at hotels.

For the dual-duct AHU where the mixing takes place at the zone, you can have a much higher number of zones since the space isn't constrained at the discharge air location so I can see that DD AHUs I've seen would be very large and tend to be CHW and HW/Steam and not DX.

So I think it's probably the best approximation to use the multizone template.

The chiller idea would give another approach but could have part load performance different than the DX system would have, but also a way to attempt a workaround.

David

David S. Eldridge, Jr., P.E., BEMP, BEAP, HBDP, GGF/A
Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman|Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers

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From: Melissa Crowe <MCrowe at cmta.com>
Sent: Tuesday, June 14, 2022 4:15 PM
To: David Eldridge <DEldridge at grummanbutkus.com>; John Aulbach <jra_sac at yahoo.com>; equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Dual Duct with package Cooling

I replied too fast the multi zone is only DX will not allow CHW.

However this is not thermally equivalent to Dual Duct where you can cool one zone while heating the other with out reheating.

Melissa Crowe, BEMP, LEED AP
Sr Mechanical/Energy Engineer
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From: David Eldridge <DEldridge at grummanbutkus.com<mailto:DEldridge at grummanbutkus.com>>
Sent: Tuesday, June 14, 2022 5:06 PM
To: Melissa Crowe <MCrowe at cmta.com<mailto:MCrowe at cmta.com>>; John Aulbach <jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Dual Duct with package Cooling

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Does it let you pick DX for the multizone AHU type?

David

David S. Eldridge, Jr., P.E., BEMP, BEAP, HBDP, GGF/A
Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman|Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
Energy Efficiency Consultants and Sustainable Design Engineers

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From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of Melissa Crowe via Equest-users
Sent: Tuesday, June 14, 2022 3:19 PM
To: John Aulbach <jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Dual Duct with package Cooling

Hi John

If by packaged Cooing you mean Air Cooled DX then, how about trying:

  *   Dual Duct system w. CHW
  *   "Chiller" =  Air cooled with appropriate compressor type (recip or scroll) and count
  *   Pump power = 0
  *   CHW supply temperature = ~ DX evaporator T

Good luck

Melissa Crowe, BEMP, LEED AP
Sr Mechanical/Energy Engineer
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From: John Aulbach <jra_sac at yahoo.com<mailto:jra_sac at yahoo.com>>
Sent: Tuesday, June 14, 2022 1:54 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Dual Duct with package Cooling

A friend of mine asked me about such a system. I looked it up, and lo and behold, eQuest doesn't this as a system.

Is there any equivalent system that can dynamically mimic this?

Thanks,

John R. Aulbach, PE
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