[Equest-users] 90.1 App G Fan Power and EER Calculations

[Paul Diglio]

I received a comment back from a recent LEED submission.  The reviewer required 
that I calculate pfan per G3.1.2.9.  I didn't argue since this increased my 
baseline energy consumption and increased my proposed savings.

 Paul Diglio, CEM, CBCP


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


www.pdigliollc.com




________________________________
From: Maria Karpman <maria.karpman at karpmanconsulting.net>
To: Nick Caton <ncaton at smithboucher.com>; Paul Riemer 
<Paul.Riemer at dunhameng.com>; Steve Burley <steve.burley at csa-eng.biz>; 
equest-users at lists.onebuilding.org
Sent: Thu, May 31, 2012 11:35:41 AM
Subject: Re: [Equest-users] 90.1 App G Fan Power and EER Calculations


Nick, Steve and Paul,
 
I believe that using ARI fan power in EIR calculations is the way to go, because 
the efficiency tables in 90.1 Section 6 show the required performance at ARI 
conditions (see the last column in each table), not at the project conditions. 
Here is the related abstract from 90.1 Section 6:
 
6.4.1.1 Minimum Equipment Efficiencies—Listed
Equipment—Standard Rating and Operating Conditions.
Equipment shown in Tables 6.8.1A through 6.8.1G shall have
a minimum performance at the specified rating conditions
when tested in accordance with the specified test procedure.
 
When a packaged system that meets 90.1 efficiency requirements at ARI conditions 
is installed in a project where the fan power is higher than in ARI testing 
procedure (e.g. projects with more extensive ductwork, air filters, energy 
recovery, etc.), it will have a lower actual EER than what’s listed in Section 
6. However, this wouldn’t make the installation incompliant with mandatory 
efficiency requirements in 90.1 Section 6. In my experience, LEED reviewers do 
comment on EIR calculations if EIR is not what they expect. However, using 
Appendix G fan power in baseline EIR calculations typically results in a more 
stringent baseline (lower EIR), so they do not insist on changing it.  
 
Thanks,
 
Maria
 
From:equest-users-bounces at lists.onebuilding.org 
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Thursday, May 31, 2012 9:56 AM
To: Paul Riemer; Steve Burley; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] 90.1 App G Fan Power and EER Calculations
 
Hi Paul!
 
I maintained the exact same position for a long while, though I thought I was 
the vocal minority =)!  Ultimately, you can argue for/against either approach as 
having different advantages of ‘correctness.’  I’ve heard future addenda or 
versions of 90.1 may address the conundrum by stipulating something more 
simplistic than either approach, like a uniform “factor” to come up with 
compressor/condenser energies from the total consumption.
 
My final position is both approaches make sense, and for different reasons – 
modelers should use whichever they feel most comfortable defending should their 
methodology come into question.  My LEED reviewers have to this point taken zero 
interest in which approach I’ve used in my calculations, after using both, so I 
take it this degree of nuance is probably not on their usual checklists.  I’ve 
switched over to the ARI approach for a few reasons, but not because I feel a 
Pfan-based approach is ‘wrong.’
 
Best wishes,
 
~Nick
 
 
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:Paul Riemer [mailto:Paul.Riemer at dunhameng.com] 
Sent: Thursday, May 31, 2012 7:29 AM
To: Nick Caton; Steve Burley; equest-users at lists.onebuilding.org
Subject: RE: 90.1 App G Fan Power and EER Calculations
 
Nick, Steve, and list,
I think I concur more with Steve. If you use Nick’s approach to calculate the 
cooling EIR by subtracting out ARI rated fan power from the 90.1 EER AND then 
model the 90.1 fan power limits directly, you will be modeling a packaged unit 
that does not comply with the package EER. 

I could see using other splits of fan and cooling, but a baseline model should 
comply with both limits.
 
Paul Riemer, PE, LEED AP BD+C
DUNHAM
 
From:equest-users-bounces at lists.onebuilding.org 
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Tuesday, May 29, 2012 10:51 AM
To: Steve Burley; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] 90.1 App G Fan Power and EER Calculations
 
Steve,
 
There are two schools of thought for dealing with fan power in cooling 
efficiency calcs.  The first pulls away the baseline fan power Pfan, as you’re 
describing, and the other instead pulls out a fan energy draw based on ARI 
testing procedures…  400 CFM/ton à 365W/1000CFM.  I follow the latter these 
days, but see both as viable.
 
The two approaches result in similar results when your Pfan calculation doesn’t 
involve a lot of static pressure adders.  When it does, the approaches diverge 
in a fashion that may be either problematic or helpful in a LEED rating sense.  
Attached discussion sums up things further, includes an outline of an ARI-based 
approach. You can find more discussions and read into advantages/disadvantages 
to both approaches in the mailing list archives.
 
That said, I haven’t checked your math or references but the procedure you’ve 
roughly outlined sounds alright for a Pfan approach.  There are steps in between 
what you’ve written for correctly coming up with Pfan, but I take it that’s 
implicit.
 
~Nick
 
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 Steve Burley
Sent: Tuesday, May 29, 2012 6:37 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] 90.1 App G Fan Power and EER Calculations
 
I’m sure this must have been asked before but I cannot find an answer in the 
archives – if there is one please point me to it.
 
I have interpreted the requirements of 90.1, App. G to split the EER of cooling 
equipment with a supply fan into its components to model the fan energy 
separately as follows:
 
1.       Say a space has a cooling load of 80,000Btu/h and the system is 
packaged single zone, EER – 11.2.
2.       Calculate airflow for 20°F temperature difference – 3708cfm
3.       Calculate fan bhp from Table G3.1.2.9 – 3.49bhp
4.       Calculate fan power as per G3.1.2.9 – 2972W
5.       Calculate gross input power from load and EER – 7143W
6.       Subtract 4 from 5 for compressor/condenser input power – 4171W
7.       Convert to EIR – 0.1779
 
This appears to make sense from reading App. G but ends up with high fan power 
consumption and low space cooling loads. Am I wrong here?
 
Thanks,
 
Steven Burley
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