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

[Paul Diglio]

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 | Facebook | Twitter | LinkedIn  
 
 
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 
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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