[Equest-users] Equest - adding Heat Recovery to VAVS system

Bishop, Bill bbishop at pathfinder-ea.com
Wed Jun 5 09:51:38 PDT 2013


Ginnie,

Higher fan energy and cooling energy are typical results when adding heat recovery.

Consider the following changes:

*         The default 1.5" static on both sides of the HRV adds a lot of fan energy. You need to determine if this is reasonable and whether or not you should adjust the system fan power/static.

*         ERV-RUN-CTRL is set to "When minimum OA". You are not simulating an economizer because OA-CONTROL is "Fixed Fraction". Therefore, you are always running the OA through heat recovery when the system is running, adding fan energy and cooling energy. Determine how the actual design will be controlled. OA temperature or OA enthalpy are typical.

*         ERV-OA-FLOW is entered as 86,000 cfm, but the SV-A report shows only ~30,000 cfm OA. So you added a huge amount of OA when you added the HRV, which is probably not what you intended, and which contributed to the energy penalty.
Unrelated observations:

*         Your plug load energy is low - only 1/10th your lighting energy. This is unusual and probably not reasonable. (They are nearly equal in most of my models.)

*         Your ground floor surfaces are modeled as exterior surfaces, rather than underground. This will most likely increase your cooling load in the cooling months and skew the envelope loads the rest of the year. (I'm assuming the school is slab-on-grade.)

Regards,
Bill

William Bishop, PE, BEMP, BEAP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
bbishop 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: Ginnie Schofield [mailto:GSchofield at edaengineering.com]
Sent: Wednesday, June 05, 2013 11:58 AM
To: Bishop, Bill; equest-users at lists.onebuilding.org
Subject: RE: Equest - adding Heat Recovery to VAVS system

Adding correct .inp file for my question

Ginnie

From: Bishop, Bill [mailto:bbishop at pathfinder-ea.com]
Sent: Wednesday, June 05, 2013 9:32 AM
To: Ginnie Schofield
Subject: RE: Equest - adding Heat Recovery to VAVS system

You attached the wrong input file. I don't know why two are created for all projects but you need to send the larger file.

Regards,
Bill

William Bishop, PE, BEMP, BEAP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
bbishop 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] On Behalf Of Ginnie Schofield
Sent: Wednesday, June 05, 2013 11:22 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Equest - adding Heat Recovery to VAVS system

Equest Users:

In my school model, I have added the Heat Recovery option to my VAVS system in the current model, and it throws results clear out of line, increasing electric power usage almost 3 times, with increased  ventilation fan operation and space cooling year round, which shouldn't be necessary in Wyoming.

Looking for methods to modify input and correct these obviously errant results.  There has been some discussion here earlier this week, tried a couple of the suggestions, without acceptable results.  If adding another system to handle the heat recovery or adding smaller heat recover to each zone is the right answer, please share the method for creating the new system in detailed edit mode.

Thank you in advance for your time and suggestions.


GINNIE SCHOFIELD
ENGINEERING DESIGN ASSOCIATES
(Ph) 307-266-5033   (Fx) 307-234-3805



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