Hi everyone, I'm a bit confused about the correct way to calculate BL fan power. The building has 6 stories and therefore 6x System 7 in the BL. In the Proposed there's just 1 CAV for the whole building. The proposed CAV is fully ducted, has filters in supply ducts and exhaust ducts, a heat recovery device and sound attenuation. So theres a long list of applicable power drop adjustments. My question is: Are these only applicable once or for every single BL system? So in my mind there are 3 possibilities: 1. Summarize all supply air flow rates -> calculate P_fan with all Pressure Drop Adjustments -> P_single_fan = P_fan * SA flow rate / summarized SA flow rates 2. Calculate P_fan individually with all Pressure Drop Adjustments 3. Calculate P_fan individually with Pressure Drop Adjustments, but count the "shared" Pressure Drop Adjustments like heat recovery device, sound attenuation only with 1/6. Would be great to get some help here.

Post a reply

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 10/12/2011 - 14:39

Your number 2 is closest to the correct approach. Calculate P_fan individually based on supply cfm of each BL system with all Pressure Drop Adjustments, except no pressure drop adjustment should be taken for heat recovery where it is not required in the BL. See footnote to Table G3.1.2.9.

Maya Karkour

EcoConsulting

LEEDuser Basic Member

549 thumbs up

Wed, 10/19/2011 - 12:54

Interesting thread.. One question though: You might have scenarios whereby you have 8 systems for the proposed (depending on the design) and 5 systems for the baseline (depending on the number of floors). "Zone A" (served by HVAC System P1) in the proposed has a ducted return air, whereas "Zone B" (served by HVAC System P1) has a free return. Both zones ended up in the Baseline being served under the same system B1 (same floor). Do we then have to adjust the baseline fan powers corrections of system B1 to accommodate for the ducted return, knowing that Zone 1 has a ducted return in the proposed but Zone 2 does not? Thanks!

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 10/19/2011 - 13:44

The pressure drop adjustment of 0.5 is only applied to the return CFM for zone A. It would not be applied to return CFM for zone B. Refer to Table 6.5.3.1.1A which defines CFMd.

Maya Karkour

EcoConsulting

LEEDuser Basic Member

549 thumbs up

Thu, 10/20/2011 - 09:04

Thanks Marcus, However, my understanding was that I should enter the adjustment on the System level (AHU) and not on the zone (I think that's the way it is done using eQUEST).

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Fri, 10/21/2011 - 16:49

The information is entered at the system level. The pressure drop is not entered directly in eQUEST. It is included in the calculation you do to determine the kW/cfm you enter in eQUEST. To calculate this value determine the total kW of all fans, then divide by the supply cfm and enter the kW per cfm in eQUEST at the system level. There is a calculator in the Documentaion Toolkit related to Appendix G calculations for fan power. So for example, assume your system serving zones A and B has a total supply cfm of 1000 and the return cfm is 500 each. Enter 1000 in the column CFMs, the appropriate pressure drop in the PD column (0.5 for zone A and 0 for zone B) and the CFMd (500 each) for each zone in that column. The wattage should then be calculated as 1,208.3 watts. In eQUEST you enter 1.21 kW/1,000 cfm = 0.00121 kW/cfm at the system level.

Santiago Rodriguez

Revitaliza Consultores

LEEDuser Basic Member

47 thumbs up

Thu, 02/09/2012 - 15:39

Hello Marcus, I am trying to find this documentation toolkit related to the Appendix G calculations for fan power, but cannot find it. Could you please tell where is it? Many thanks!

Morteza Kasmaei

Principal

Climatic Design Inc.

LEEDuser Basic Member

18 thumbs up

Thu, 02/09/2012 - 17:49

Hi Marcus, I have two questions regarding the calculator. 1- Why you assumed 0 pressure drop for zone B. 2- Is always total return cfm (CFMd) is equal to total supply cfm. Thanks

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Sun, 02/12/2012 - 19:56

Santiago, Go to the top of the page and click on Documentation Toolkit.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Sun, 02/12/2012 - 20:06

Morteza, 1 - see citation above regarding 0 pressure drop in zone B. 2 - not always

Add new comment

To post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.

You are currently logged in under an enterprise account

FAQs about EAp2 :

fan power calculation

You rely on LEEDuser. Can we rely on you?

Add new comment