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NC-2009 EAp2:Minimum Energy Performance

Fan Power and Fan Power Adjustment (FPA)

Greetings, In the project we are modeling, the following issues are still not quite clear for us and we'd appreciate any advice on the matter. Baseline system is 8. The Proposed AHU systems are with fully ducted supply, return and exhaust parts. Their AHUs are provided with filter F7 (MERV13), rotary heat recovery device (HRD) and sound attenuator on the supply side. The questions are: 1. By applying the PD adjustments as per table 6.5.3.1.B, should we take the fully ducted PDA only once or we should apply it twice - for supply and return. Also regarding HRD, should we apply the PDA for the supply and for the return side or only once. 2. Baseline system 8 has a fan power related to the PFBs. How to estimated these powers. All comments and advices are highly appreciated. Thanks

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
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Mon, 11/07/2016 - 14:54

1. The PDA is for fully ducted return so it only counts once. 2. See G3.1.3.14 So it sounds like you can claim a PDA for fully ducted return (0.5), MERV 13 filters (0.9), and sound attenuation (0.15). Keep in mind that you can only claim the fully ducted return PDA if 100% of the returns are ducted. If you have one transfer grill or plenum return then you can't claim it (see the Under's Manual). Also you can only claim a PDA for heat recovery if it is required in the Baseline according to G3.1.2.10. It does not matter if there is heat recovery in the Proposed system.

Tue, 11/08/2016 - 13:20

Marcus, thanks a lot for the reply. Could you please clear also what is understood by airflow control devices and in what situationthey it could be applied. Is this closing or adjusting dampers on the return side and in which place. I'm sorry, but without some more explanation, I could've missed or unproperly apply them. Thanks.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Tue, 11/08/2016 - 15:21

That refers to situations only where the airflow is modulated to maintain relative negative or positive space pressure (e.g. lab, operating room). There may be a few other applications but this is rarely installed in most standard HVAC systems. The User's Manual has a good discussion of this I think. This one is often incorrectly applied.

Tue, 11/08/2016 - 15:25

Thanks a lot Marcus, I'd like to ask again about System 8 and the fan power assigned to fan powered VAV boxes - how to estimate it. Thanks.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Tue, 11/08/2016 - 15:42

ASHRAE 90.1-2007 Appendix G3.1.3.14 tells you how to model these boxes in the Baseline for a System #8.

Tue, 11/08/2016 - 15:48

Thanks Marcus, Sorry for didn't check about it. I do applogize

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