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

Paul Riemer Paul.Riemer at dunhameng.com
Thu May 31 05:28:44 PDT 2012

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

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


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.

[cid:image001.jpg at 01CD3EFC.8314EDC0]


Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
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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?


Steven Burley

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