[Equest-users] Fw: ERV on OA-From-System Comments from Jeff Hirsch
Brian Fountain
bfountain at greensim.com
Thu Jun 6 11:53:21 PDT 2013
I will jump into this thread late. What the OA-FROM-SYSTEM keyword does in DOE-2 is to set the incoming outdoor air temperature of the system using the keyword (the borrowing system) equal to the return air temperature of the system it specifies it is getting its OA from (the lending system). That is all. Thus there is no real transfer of air using this keyword.
Regarding using an ERV with the OA-FROM-SYSTEM keyword, the “air” is not returned to the lending system (see above) so there is no or little heat to recover in the exhaust airstream. There are 2 possible workarounds for this. I have used the frost control “preheat exhaust” in the ERV keywords to set the exhaust temperature from which heat can be recovered. I then use electric heating for this exhaust preheat and put that preheat on a separate, zero cost, electrical meter. I then compare the heat added on the dummy meter to the internal gains in the actual space to ensure they are comparable. Alternately, you could add a dummy internal load in the lending system space to increase the exhaust air stream temperature to give you your heat for heat recovery.
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Tuesday, June 04, 2013 4:01 PM
To: Rick Goeres; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Fw: ERV on OA-From-System Comments from Jeff Hirsch
Rick:
Thanks for the response. I have tried what you are suggesting and have not been successful in modeling the same energy recovery results that manual calculations indicate should be achieved. It seems to me that the return airflow is from the zone that the DOAS is attached to and not the other zones, as indicated by the return air temperature. In other words, it lloks like the only heat availabe for recovery is from the zone or dummy zone served by the DOAS.
I would be interested in looking at one of your projects if you care to share one.
If the eQuest developer, Jeff Hirsh tells me that an OA-From with an ERV is not supported, I will have to take him at his word. He did not say what aspect is not supported. Like I said, in the past I have chopped up the ERV and attached a smaller one to each system served and achieved the results that my manual calculations indicated would be achieved. I am just at a loss with a DOAS that has chilled and hot water coils as well as an ERV, since the coils have been sized assuming that the ERV conditions the air previous to it entering the coils.
Without the ERV on the DOAS my discharge air temperature in the winter (Westfield, MA) is as low as 30 degrees and the chilled beams, modeled as IU, cannot supply the required discharge air temperature. If I try to remove the coils from the DOAS and chop them up and increase the heating/cooling capacity of each chilled beam system, my discharge air off the DOAS drops as low as -5 in the winter and again the chilled beams with their mini ERV's cannot condition this air.
Any ideas?
Thank you,
Paul Diglio, CEM, CBCP
87 Fairmont Avenue
New Haven, CT 06513
203-415-0082
www.pdigliollc.com
_____
From: Rick Goeres <RickG at musgrovepa.com>
To: Paul Diglio <paul.diglio at sbcglobal.net>; equest-users at lists.onebuilding.org
Sent: Tue, June 4, 2013 11:06:19 AM
Subject: RE: [Equest-users] Fw: ERV on OA-From-System Comments from Jeff Hirsch
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
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MUSGROVE ENGINEERING, P.A.
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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.
cid:image001.png at 01CE0924.38506AB0
Stormy L. Shanks, PE
Mechanical Engineer
2882 106th St, Des Moines, IA 50322
D 515.334.4315
<http://www.kjww.com/> web | <http://www.facebook.com/kjwwengineering> Facebook | <http://twitter.com/kjww> Twitter | <http://www.linkedin.com/company/kjww-engineering-consultants> 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 <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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