[Equest-users] Fw: ERV on OA-From-System Comments from Jeff Hirsch

Rick Goeres RickG at musgrovepa.com
Tue Jun 4 08:06:15 PDT 2013


I have specified a DOAS as a single zone unit before and then designated it as the OSA From System in all of the other HVAC systems.  If I leave the Design Outdoor Air and Exhaust flow inputs empty under the heat recovery tab, the outside air from the other HVAC systems does not show up in the ERV.  But if I total the design outside air values and then input these into the Design Outdoor Air and Exhaust flows, the ERV works and seems to be representative.  

 

  Rick Goeres, PE, LEED AP

 

MUSGROVE ENGINEERING, P.A.
Web: www.musgrovepa.com <http://www.musgrovepa.com/> 
234 S. Whisperwood Way, Boise, ID 83709            
Ph: 208.384.0585 x324      Fx:208.384.0765
Over 35 Years of Engineering Excellence

 

 

 

 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Monday, June 03, 2013 5:54 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Fw: ERV on OA-From-System Comments from Jeff Hirsch

 

 

 

 

Stormy:


In the past when I have modeled just an DOAS that did not have any heating or cooling capacity with and ERV was to add an ERV to each zone system that the DOAS fed.  I used the same kw/cfm that the DOAS system had.  So I chopped up the DOAS with it's ERV into smaller ERV's on each system.  This seemed to work good.

The problem with the project that I am working on now, is that the DOAS feeds chilled beams.  The DOAS chilled water coil and heating coil is sized in the design with the assumption that and ERV is conditioning the outside air.  The DOAS has to dehumidify the air because the chilled beams cannot remove moisture as there is no provision for condensate removal.  If I remove the ERV from the DOAS, the chilled and hot water coils are not large enough to condition the OA before it reaches the ERV on the chilled beams and I can't add a chilled or hot water coil to the ERV's on the chilled beams.  So I loose the additional heat/cool capacity designed into the DOAS.

Confusing.

Regards,

 

Paul Diglio, CEM, CBCP

87 Fairmont Avenue
New Haven, CT 06513
203-415-0082

 

www.pdigliollc.com

 

 

________________________________

From: Stormy L. Shanks <shankssl at kjww.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>
Sent: Mon, June 3, 2013 7:15:24 PM
Subject: RE: [Equest-users] ERV on OA-From-System Comments from Jeff Hirsch

Wow, thank you for sharing that. That’s definitely a bummer. I just did a test on a model that I did with DOAS where I had defined an ERV in the DOAS system. I deleted the ERV from the system, and my energy was lower than when the ERV was included. Not good. I should have known better. I suppose I will start modeling ERV/DOAS settings in spreadsheets outside of eQUEST. Or in other software.

 

 

Stormy L. Shanks, PE
Mechanical Engineer

2882 106th St, Des Moines, IA 50322
D 515.334.4315

web <http://www.kjww.com/>  | Facebook <http://www.facebook.com/kjwwengineering>  | Twitter <http://twitter.com/kjww>  | LinkedIn <http://www.linkedin.com/company/kjww-engineering-consultants>  

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Monday, June 03, 2013 5:17 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] ERV on OA-From-System Comments from Jeff Hirsch

 

Just wanted to share an e-mail from Jeff.  I did not know that an ERV on a OA-From system was not supported by eQuest.  That explains why I could never get the correct airflows on this type of design.

Unfortunately almost every project I work on does specify a VAV DOAS with an ERV to supply ventilation air to some type of HVAC system, such as VRF indoor coils, chilled beams or PTHP units.  I will have to try the work around Jeff suggested.

 

Paul Diglio, CEM, CBCP

87 Fairmont Avenue
New Haven, CT 06513
203-415-0082

 

www.pdigliollc.com

 

 

----- Forwarded Message ----
From: Jeff Hirsch <James.J.Hirsch at gmail.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>
Sent: Mon, June 3, 2013 12:17:58 PM
Subject: Re: [Equest-users] OA From System Question

Setting your OA system (ERU1) to be vav and having the ERV on it will not work correctly.  If you need ERV you must place your ERV in the IU system and use that system to supply the conditioned OA.  ERV on a OA-FROM system is not supported.  VAV on an OA-FROM system is possibly not what you want but I cannot tell what you are trying to do.  An IU system has a central constant volume air supply with each zone then having zone coil to do the zone thermostat controlled conditioning via room air flow induced as a constant ratio supply air fro the IU (the induction-ratio). So it seems you can use the IU system as your ERU system supplying the zones. If there is some other reason you used an OA-FROM system, then perhaps my suggestions don’t apply, but the ERV and VAV comments always apply.

 

________________________________

Jeff Hirsch
James J. Hirsch & Associates
12185 Presilla Road -  Camarillo, CA 93012-9243 USA
phone: (805) 553-9000 mobile: (805) 532-1045 fax: (805) 532-2401
email: James.J.Hirsch at gmail.com

 

From: Paul Diglio <mailto:paul.diglio at sbcglobal.net>  

Sent: Monday, June 03, 2013 6:11 AM

To: equest-users at lists.onebuilding.org 

Subject: [Equest-users] OA From System Question

 

Morning:

I am trying to model a chilled beam system as induction units.  The primary air is supplied by an ERU.  I set the outside air to 0 on the chilled beams HVAC systems tab.

In the chilled beam zone tab I set the outside air to the primary CFM and the overall CFM to the induced air flow.

Per the eQuest help menu, "The sum of the OA requirements for all SYSTEMs that reference an OA-FROM-SYSTEM is used to set the referenced OA-FROM-SYSTEM value for MIN-OUTSIDE-AIR, SUPPLY-FLOW as well as adjust the referenced OA-FROM-SYSTEM directly served ZONE maximum and minimum flows for both heating and cooling." 

But per my hourly reports, the ERU is not supplying the necessary amount of primary air and in the summer the ERU flow drops to .01 CFM.

Attached are the project files.  Any ideas?

Thank you,

 

Paul Diglio, CEM, CBCP

87 Fairmont Avenue
New Haven, CT 06513
203-415-0082

 

www.pdigliollc.com 

 

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