[Equest-users] 90.1 App G Fan Power and EER Calculations
Paul Diglio
paul.diglio at sbcglobal.net
Thu May 31 12:35:27 PDT 2012
Maria:
Yes, I agree. I use the supply fan power at the design static from the
manufacturer's data sheet for the proposed model. I then re-calculate the unit
EER without the supply fan power, which raises the EER and lowers the EIR.
Perhaps I am misunderstanding the thread. It seems that some people are
talking about the baseline because they reference Section 6. So it appears
that some simulators are using the ARI fan rating instead of using G3.1.2.9 to
calculate pfan for the baseline? It doesn't appear to be any wiggle room in
G3.1.2.9 as it states:
"G3.1.2.9 Supply Fan Power. System fan electrical power
for supply, return, exhaust, and relief (excluding power to fanpowered
VAV boxes) shall be calculated using the following
formulas:"
Is this your understanding of the thread? I am a bit confused.
Regards,
Paul Diglio, CEM, CBCP
87 Fairmont Avenue
New Haven, CT 06513
203-415-0082
www.pdigliollc.com
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: Paul Diglio <paul.diglio at sbcglobal.net>; 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 2:57:23 PM
Subject: RE: [Equest-users] 90.1 App G Fan Power and EER Calculations
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
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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