[Equest-users] DOAS+DCV+ERV problems - no dummy zone heat recovery

[Bishop, Bill]

As far as I know (AFAIK), no one has posted to equest-users to describe a way to accurately model heat recovery using an OA-FROM-SYSTEM DOAS assigned to a dummy zone. The main problem being that the OA-FROM-SYSTEM uses the dummy zone temperature as the return air temperature to the ERV.
In the case of this particular model, I think a more reasonable workaround would be to model energy recovery at each of the VAV units instead of modeling a dedicated DOAS. Model each VAV system with SELF-CONTAINED ERV-FANS and distribute the DOAS fan power amongst the VAV systems.

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer
134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 698-1956                        F: (585) 325-6005
bbishop at pathfinder-ea.com             www.pathfinder-ea.com
Carbon Fee and Dividend - simple, effective, and market-based.

-----Original Message-----
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of jacob goodman
Sent: Thursday, February 04, 2016 10:32 AM
To: Jones, Christopher <Christopher.r.Jones at wspgroup.com>; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DOAS+DCV+ERV problems

Chris,
Thanks mucho!!! Switching from "Fixed Setpoint" to "Mixed Air Reset" 
seems to have totally cleared up the problem. The model now shows reasonable savings without any unmet hours. I have had many models run with no problem using the Fixed Setpoint controls, but not this one. I agree that Float almost always causes issues.
Thank you so much, you truly saved my day, Jacob


On 2/4/2016 8:13 AM, Jones, Christopher wrote:
> Quoting Brian Fountain's response of January 28:
>
> "The default settings for heat recovery control is'float' which always maximizes heat recovery, even if it reduces free cooling. Changing this to 'mixed air reset' will help.
>
> Also, on the 2nd heat recovery tab, the default is 1" of static added to the supply fan (on top of whatever you have on the fan tab) to account for the added fan power to push the air through the heat recovery device.  "
>
> I changed your model to 'mixed air reset' and the cooling energy dropped significantly.
>
> Christopher Jones, P.Eng.
> Senior Engineer
>
> WSP Canada Inc.
> 2300 Yonge Street, Suite 2300
> Toronto, ON M4P 1E4
> T +1 416-644-4226
> F +1 416-487-9766
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>
> www.wspgroup.com
>
> -----Original Message-----
> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] 
> On Behalf Of jacob goodman
> Sent: Thursday, February 04, 2016 9:50 AM
> To: equest-users at lists.onebuilding.org
> Subject: [Equest-users] DOAS+DCV+ERV problems
>
> Dear Community,
> I am working on a model of a 33 story building served by separate VAV system for core and perimeter zones. Core zones with VAV terminal units and perimeter with fan powered boxes. All areas are served by DOAS via the dummy zone/"OA from system" work around. I have added DCV return sensor to the non-DOAS systems only. These systems showed appropriate savings from this before I added the DOAS and seem ok after as well. The problem comes when I add the ERV to the two DOAS systems. I am using ERV settings and controls that are well tested and have worked in similar models. That is Enthalpy wheel, 56% Sen.&Lat. effectiveness, OA Exhaust DT at 5deg, fixed set point controls and 0.5inH2O pressure drop with premium fans.
>
> The issues is that as soon as I activate on the ERV the heating energy drops by ~90% and cooling/pumps/fans triple or more. This creates 4,000+ unmet hours and overall building energy use is up 40%.
>
> It seems like a massive heat load is being added to the system because of the ERV, but I cant see why or how. I checked fan kW sizing and that does not go up. Neither does supply air flow.
>
> I would work on debugging this for as long as needed, but the deadline looms! Attached is the model for reference. Simply turn "Recover Exhaust?" to No to see the difference.
> Jacob
>
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