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

[Maria Karpman]

Paul, 

 

I think we are all in agreement that Pfan must be calculated as described in G3.1.2.9 when modeling the baseline fans. This discussion is about extracting the fan energy from the rated EER when modeling system efficiency (EIR) to satisfy G3.1.2.1 quoted below:

 

G3.1.2.1 Equipment Efficiencies. All HVAC equipment

in the baseline building design shall be modeled at the minimum

efficiency levels, both part load and full load, in accordance

with Section 6.4.Where efficiency ratings, such as EER

and COP, include fan energy, the descriptor shall be broken

down into its components so that supply fan energy can be

modeled separately.

 

G3.1.2.1 refers to efficiency requirements in Section 6.4, which in turn refers to efficiency at the rating conditions and not the project’s design conditions (see 6.4.1.1 included in my earlier email below). If the efficiency requirements in 6.4 were for the design conditions, then I would agree that Pfan should have been used to convert from EER to EIR.

 

Maria 

 

From: Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: Thursday, May 31, 2012 12:53 PM
To: Maria Karpman; Nick Caton; Paul Riemer; Steve Burley; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] 90.1 App G Fan Power and EER Calculations

 

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

 

cid:489575314 at 22072009-0ABB

 

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

cid:489575314 at 22072009-0ABB

 

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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