[Equest-users] Cooling Increase DCV and ERV Measures

Paul Diglio paul.diglio at sbcglobal.net
Fri May 31 08:02:56 PDT 2013


Nina:

Below is a GBCI review comment on a project where I provided Enhanced 
Commissioning services, but not the energy model.  It might help.


7. Table 1.4.2 and the system Input Data reports for the Proposed model indicate 
that demand control ventilation (DCV) was modeled for credit in the Proposed 
case; however, it is unclear how the outdoor air ventilation rates were 
determined in each case. Table G3.1.4 in the Baseline building column allows 
schedule changes for DCV as approved by the rating authority, and as the rating 
authority, GBCI requires that, for spaces taking credit for DCV in the actual 
design, the outdoor air ventilation rates in the Baseline model must be modeled 
using the minimum ASHRAE Standard 62.1-2007 rates during periods of peak 
occupancy, and the outdoor air ventilation rates in the Proposed model must 
reflect the outdoor air ventilation rates from the actual design during periods 
of peak occupancy. For example, if credit for DCV is reflected for AHU-3 in the 
Proposed model, the minimum outdoor air ventilation rates must reflect 497 cfm 
in the Baseline case and 1,000 cfm in the Proposed case, based on the values 
indicated in IEQp1: Minimum Indoor Air Quality Performance. For spaces taking 
credit for DCV in the actual design, revise the Baseline model to reflect the 
ASHRAE Standard 62.1-2007 minimum outdoor air ventilation rates and revise the 
Proposed model to reflect the outdoor air ventilation rates from the actual 
design. For all other spaces (no DCV control or DCV control modeled in both the 
Proposed and Baseline model), confirm that the outdoor air ventilation volumes 
are modeled identically, using the actual as-designed ventilation rates (not the 
ASHRAE Standard 62.1-2007 minimum ventilation rates) in the Proposed and 
Baseline models, as required by Section G3.1.2.5. In addition, verify that all 
HVAC systems in both the Proposed and Baseline cases are modeled with zero 
outdoor air flow when the HVAC fans are cycled on to meet unoccupied setback 
temperatures, unless health or safety regulations mandate an alternate minimum 
flow during unoccupied periods (in which case, the unoccupied minimum outdoor 
air ventilation rates must be modeled identically in each model). Further, 
provide the revised total outdoor air ventilation volume (in units of cfm) for 
the Proposed and Baseline models in Table 1.4.2, and provide a revised Input 
Data report for each system in the Proposed and Baseline models reflecting the 
changes. Note that the total minimum outdoor air ventilation volume in the 
Baseline model must never be greater than the Proposed model.
Regards,

  
Paul Diglio, CEM, CBCP


87 Fairmont Avenue
New Haven, CT  06513
203-415-0082


www.pdigliollc.com




________________________________
From: Daniel Knapp <danielk at arborus.ca>
To: Netty Nina <nnina at ers-inc.com>
Cc: "equest-users at lists.onebuilding.org" <equest-users at lists.onebuilding.org>
Sent: Fri, May 31, 2013 10:19:04 AM
Subject: Re: [Equest-users] Cooling Increase DCV and ERV Measures

I don't know if this is relevant to your situation, but we recently ran into a 
problem where turning on DCV increased the OA intake for a VAV system.  The 
model is at an early design stage for core and shell and the OA hasn't been 
specified yet so we were using eQuest OA autosizing.  The OA without DCV was 
sized to meet the critical zone requirement at the full design supply flow 
rate.  When using DCV, the OA is sized to meed the critical zone on an 
hour-by-hour basis, and as the supply flow rate drops, the outdoor air 
requirement can go up if the OA fraction for the critical zone approaches 1 
leading to an increase in overall OA.  Lesson learned: don't rely on eQuest to 
autosize the OA as it does the OA sizing against the full design supply flow 
rate which may not be the worst case condition. 


Cheers,
Dan

—
Daniel Knapp, PhD, P Phys, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue 
Ottawa, ON, K1S 1V9 
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740




On 2013-05-30, at 10:23 PM, Netty Nina <nnina at ers-inc.com> wrote:

> Hi eQuesters,
>  
> The next two questions have been asked on here multiple times, but I have 
>scourged the list and haven’t found a resolution. My building is a school in New 
>England.
>  
> I have a DCV measure that shows an increase in cooling. My thought is that DCV 
>is taking precedence over the economizer. Is there a way to force eQuest to have 
>economizer priority or is there another issue going on?
>  
> The other issue is in the Heat Recovery. It also shows an increased cooling 
>load for the building. I tried setting it on an ERV Schedule and limiting it to 
>the heating season. I tried playing with the different controls. I know it’s not 
>due to the increase in fan energy needed since the majority of units already 
>have ERVs, but the efficiencies are better than code (and I also tried messing 
>with the fan energy). Someone on the bldg-sim list even suggested controlling 
>the ERV with Exhaust DT and increasing the delta-T to 20F.
>  
> I couldn’t get any suggestions to work.  How can I avoid overheating? Or is 
>there another issue?
>  
> Thanks in advance for any help you can give me.
>  
> Sincerely,
>  
> Netty
>  
>  
> Netty Nina, LEED® AP BD+C
> Project Engineer
> ERS
> 120 Water Street, Suite 350
> North Andover, MA 01845
>  
> Ph: 978-521-2550 ext. 224
> Fax: 978-521-4588
> nnina at ers-inc.com
> www.ers-inc.com
>  
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