[Equest-users] heat recovery and zone exhaust

[Keith Swartz]

Vipul,

If the supply air from the DOAS is at (or near) room temperature, and “room temperature” is about the same in the corridor as in the apartments units, then in the model I would exhaust the air from the corridor that the air goes into. Keep in mind that the energy model does not have to replicate the exact systems in the building. The energy model is to estimate the energy use of the building. As long as the (simplified) modeled system uses about the same energy use as the (complicated) actual system you will still get reasonable results.

If the DOAS supply air temperature is cooler or warmer than room temperature to help meet part of the space loads, then it gets more complicated. Most energy modeling programs, with a few special exceptions, cannot have two air systems serve the same space. In cases like that I have modeled an energy recovery system for each apartment unit instead of one big DOAS system. As long as the energy consumption is on a per cfm basis, the error from this method will be minimal. In the model the terminal unit coils will take the entire load, even though in reality part of the load will be handled by separate coils in the DOAS. If the DOAS coils have different fuel sources (like DX vs. chilled water, electric heat vs. hot water), then this approximation will be off. There will be more error if the big system modulates to meet changing conditions due to the part load curves, but as long as the systems are full on/full off the error will be minimal.

I hope this helps. Simplify as much as you can and remember that you are estimating energy usage.

Keith Swartz, PE, BEMP, LEED AP
Senior Energy Engineer | Energy Center of Wisconsin | Madison.Chicago.Minneapolis
608.210.7123 | www.ecw.org<http://www.ecw.org/>

From: Vipul Babriya [mailto:vipulbabriya at aol.com]
Sent: Thursday, September 12, 2013 3:36 PM
To: wbishop at pathfinder-ea.com; JHANSEN at ghtltd.com; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] heat recovery and zone exhaust

Hello Bill/James,

I have a typical situation for DOAS system that serves fresh air (100% OA) to corridor spaces in multifamily building. The DOAS unit is equiped with heat recovery wheel, and uses the exhaust air from apartments, i.e. exhaust from bathroom and kitchen rather than return air from corridor itself. How would i model the system that uses recovered heat from one system to another in the eQUEST.

Thanks in advance for your help.

Regards,
Vipul



-----Original Message-----
From: Bishop, Bill <wbishop at pathfinder-ea.com>
To: James Hansen <JHANSEN at ghtltd.com>; equest-users <equest-users at lists.onebuilding.org>
Sent: Wed, Dec 15, 2010 10:04 am
Subject: Re: [Equest-users] heat recovery and zone exhaust
James,

Make sure to NOT enter zonal exhaust flows if your intention is for the air to return to the ERV. Specifying zonal exhaust simulates air leaving the zone through a separate exhaust fan (think bathrooms, kitchens, clothes dryers) and not returning to the air handling unit.

Regards,
Bill

William Bishop, PE, BEMP, LEED® AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
wbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>           www.pathfinder-ea.com<http://www.pathfinder-ea.com/>
P   Sustainability – the forest AND the trees. P
________________________________
From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org?>] On Behalf Of James Hansen
Sent: Wednesday, December 15, 2010 9:59 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] heat recovery and zone exhaust

I’m having the typical issues with getting an enthalpy wheel to show appreciable savings.  I’ve adjusted some of the control sequences, and have managed to show a savings in cooling energy, but I’m getting no heating savings, which is strange, unless my building is actually asking for cold OA during the winter because of the rather large internal heat loads (my guess is that this is true).

My question is whether you HAVE to define zonal exhaust airflow rates to properly show the savings from heat recovery, or if the program knows that the exhaust will roughly match the OA delivered to the space?  Do I have to turn on exhaust tracking?

GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com<http://www.ghtltd.com/>



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