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

Thu May 31 08:35:34 PDT 2012

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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