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RE: [EnergyPlus_Support] Re: Ventilation control strategy for ASHRAE 90.1 compliance
Dear Luke,
I LOVE (thoughtful and considerate) contrariness!
On the one hand, it would not be unbelievable for a system to run a constant minimum OA that was sufficient for the exhaust fan operation. A supermarket of this size has plenty of places an exhaust damper capacity for the air to find egress without much pressurization. (I could tell you stories about pressurization!) On the other hand, it would be rather stupid to do so and the designers of this project are pretty smart.
The outdoor air for this store is provided from a central AHU that serves (almost) the entire store, so it’s not a dedicated makeup air unit. I’m glad you mentioned that, however, because it may not have occurred to me otherwise for a project that does use separate makeup air!
Thanks!
James V Dirkes II, PE, BEMP, LEED AP
<http://www.buildingperformanceteam.com/>www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Wednesday, June 11, 2014 4:24 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Ventilation control strategy for ASHRAE 90.1 compliance
As with most things involving DCV, this is a sticky situation.
I think the best indiciation is to look at how the system would operate if you were to run it in the real world in�your "Baseline" configuration. Would pumping 12,000 cfm of outdoor air into the zones in question without activating the exhaust fans overpressurize the space? Can the exhaust damper on the outdoor air unit handle 12,000 cfm, or does it require relief through the separate exhaust fans? If the Baseline configuration is not feasible, then you probably can't take credit for the savings.
Also, if outdoor air units are purely make up air units for the kitchen, then they are technically considered process energy, and therefore�unregulated under�Appendix G. And thus, required to be modeled identically between�Baseline and Proposed cases�unless an exceptional calculation measure can be demonstrated. In that case, you must demonstate that interlocking make up air and exhaust fans is not common practice, which is a hard sell.
Sorry to be contrary,
Luke
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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
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