[Equest-users] Separating Fan Energy from EER

[Bill Talbert]

Nick and Christian,
The 90.1 prescriptive performance values for unitary equipment are based on ARI rated conditions. The 90.1 baseline fan power allowance does not directly align with the fan energy used in the ARI test. The fan energy in the ARI test is based on 365 W/1000 CFM and 400 CFM/12000 Btu/h. I believe you should use your baseline system equipment capacity (Btu/h or KW) to calculate the amount of fan energy to 'extract' from the cooling equipment EER/SEER/COP rather than the 90.1 baseline fan power allowance as indicated below in step 4. If you use the 90.1 baseline fan power allowance, you could be removing a larger fan power value, making the cooling equipment more efficient in the baseline than the tested performance requires.

Also, the ARI tests are based on specific temperature conditions so you may need to adjust for project specific design conditions.

Regards,
Bill


Bill Talbert  PE, LEED(r) AP
Sustainable



AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Boulevard | Madison, WI  53719

P: 608.441.6677 | C: 608.234.3803 | F: 608.238.2614
btalbert at aeieng.com<mailto:btalbert at aeieng.com>  |  www.aeieng.com<http://www.aeieng.com/>






From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Monday, July 11, 2011 9:52 AM
To: Christian Kaltreider; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Separating Fan Energy from EER

Hi Christian,

USGBC/LEED/90.1 does not officially sanction or require any eQuest-specific procedure (nor any other program), so ultimately it falls on the modelers to know what the heck we're doing and be able to defend it in cases like this.

As a qualifier, not all efficiency ratings are fan-energy-inclusive.  For those that are, the procedure I follow (using a spreadsheet) is to basically:

1.       Using the maximum design capacity, translate the prescribed/scheduled efficiency from SEER/EER to kW input at maximum capacity.  You may have noticed there's more than one SEER equation out there... For seasonal efficiencies (SEER/AFUE), there are various formulae for conversion to steady-state efficiencies (EER/COP) that vary based on what kind of equipment you're dealing with.  You'll also find that certain equipment like heatpumps have multiple equations referenced, as there are multiple white papers published over the decades that attempt to establish a relationship between nominal seasonal efficiency and steady-state efficiency, where each study sampled different equipment from a different period of time.  What does this mean for today's LEED modeler?  There are multiple right answers (provided you know where you're coming from).  To give a more concrete response on this point, here are the equations I have collected and currently use for baseline system seasonal efficiencies (with references):


EER=f(SEER):

[Reference: NREL Building America House Simulation Protocol (Revised), citing Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations.]<http://apps1.eere.energy.gov/buildings/publications/pdfs/%20building_america/house_simulation_revised.pdf>

(AC) (Baseline Systems #1, #3, #5 & #6):

EERNET = -0.0182*SEER^2 + 1.1088*SEER

(HP-cooling) (Baseline Systems #2 & #4):

EERNET = -0.02*SEER^2 + 1.1268*SEER


COP=f(HSPF):

[Reference: Wassmer, M. (2003). A Component-Based Model for Residential Air Conditioner and Heat Pump Energy Calculations. Masters Thesis, University of Colorado at Boulder.]

(HP-heating) (Baseline Systems #2 & #4):

COPNET = -0.0255*HSPF^2 + 0.6239*HSPF


HIR = f(AFUE):

[Reference: California Energy Commission's 2005 "Nonresidential Alternative Calculation Method (ACM) Approval Manual"]

For single packaged central furnace (baseline system #3):

HIR = (.005163*AFUE+0.4033)^-1

For Boilers where 75 ≤ AFUE < 80 (Baseline systems #1, #5 &#7):

HIR = (0.1*AFUE+72.5)^-1*100

For Boilers where 80 ≤ AFUE < 100 (Baseline systems #1, #5 &#7):

HIR = (0.875*AFUE+10.5)^-1*100



*Note: The cited references above are freely accessible on the internet, last time I checked.  If anyone has a "better" equation to suggest, (knowing where the equation came from), please share!


2.       For baseline systems, calculate the system fan energy Pfan.  For proposed systems, calculate the actual system fan energy in kW.

3.       Using the system fan design airflow(s), enter the calculated fan energy as kW/CFM under airside systems tab.

4.       Subtract #2 from the cooling "kW input" in #1 - this is the "other-than-fan energy."  Using the design cooling capacity for the system, turn that into an EIR figure for input in the model.


Those who make the effort to understand what's happening have the right idea.  Relying on others' work and tools without fundamental understanding on occasion is necessary, but it's a slippery slope to be sure.

Best of luck to you!

~Nick
[cid:image001.jpg at 01CC3FB9.54A6A9D0]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Christian Kaltreider
Sent: Monday, July 11, 2011 7:43 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Separating Fan Energy from EER

Hi All,

There are strings about this subject in the archives, but they do not fully answer my questions and I am not able to open some of the key attachments.  Here is my question:  Is there a LEED-accepted method for separating out fan energy from an EER?  I am looking for how this can be done without eQUEST doing some behind-the-scenes calculations/assumptions.  There is an equation that was given in a former string, but I don't know its source or whether it is an accepted method by the reviewing committee.  Again, I am looking to be able to show how this is done by hand...not how to get eQUEST to do it for me.

Thanks very much for your help,
Christian


Christian Kaltreider, LEED AP
Energy Engineer
Sud Associates, PA
(828) 255-4691
ckaltreider at sudassociates.com<mailto:ckaltreider at sudassociates.com>



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