[Equest-users] Fan energy fundamentals - Appendix G models
Nick Caton
ncaton at smithboucher.com
Fri Feb 24 13:49:49 PST 2012
I'd feel remiss to not reiterate where I left the discussion some months ago also: The baseline VAV curve defined by 90.1 does not paint a clear picture as to what it is representing in regards to SP setpoint strategies.
I've offered some speculation as to what conditions it does seem to be based upon from the shape and the behavior it describes, but ultimately I don't believe the curves produced by eQuest or this EDR guideline are on the same playing field as the 90.1 curve: apples and oranges.
Also, I see the images have dropped off in the emails way below, for anyone picking up on the topic today... so I've attached a copy of the discussion I have including the curve images I posted to compare/contrast some of the curves under discussion.
~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: Bruce Easterbrook [mailto:bruce5 at bellnet.ca]
Sent: Friday, February 24, 2012 3:36 PM
To: Bishop, Bill
Cc: Nick Caton; R B; Paul Riemer; Equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Fan energy fundamentals - Appendix G models
One other thought, these curves are for plenum/plug fans, ie an unhoused wheel. They are not as efficient as a housed wheel, a DWDI blower. Though lack of space, sometimes poor casing and duct design on the DWDI blower can get a plenum fan closer in efficiency. Also the blades are airfoil which are more efficient than a BI blade.
Bruce Easterbrook P.Eng.
Abode Engineering
On 24/02/2012 03:35 PM, Bishop, Bill wrote:
Thanks Nick, RB, Paul,
I was interested in these curves so I could start modeling static pressure reset, AKA critical zone reset. I just tried the "Good SP Reset VSD Fan" curve and the savings were considerable versus the 90.1 Table G3.1.3.15 curve. The Good SP Reset curve also results in less fan energy than the "Variable Speed Drive FPLR" eQUEST library curve (discussed below in earlier correspondence). I did get this message but I'm choosing to ignore it for now:
**CAUTION**********************************************************************
In curve: Good SP Reset VSD Fan the dependent value
is exceeding the limits.
Value/Min/Max/First time: 1.305 0.000 1.000 12/31/24
Thanks,
Bill
From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Friday, February 24, 2012 12:51 PM
To: Bishop, Bill; R B
Cc: Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Fan energy fundamentals - Appendix G models
At first glance it looks as simple as copy-pasting into a .txt file in notepad or similar, then renaming the file extension to .inp... turns out there are a series of formatting issues that kinda threw a wrench into that line of thought.
Here's what I patched together some time back after first encountering that EDR guide. I haven't put this into practice yet for an energy model (though the guide has definitely impacted my design work), so I'd heavily advise carefully re-reading the EDR guideline's explanations of these curves before putting them to use. IIRC, some of that appendix looks like DOE2 but is really just a listing of coefficients for use beyond what's actually provided - I used my own initial judgment of what was "dollar sign" descriptive text in the INP - worth checking out before using also.
Let me know how this works out for ya, I'd appreciate if you'd share any edits you find necessary from this point.
`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> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Friday, February 24, 2012 10:46 AM
To: R B
Cc: Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Fan energy fundamentals - Appendix G models
Yes, that is the guide linked to below. I would like a copy of the fan curves shown in Appendix 5. I was hoping to save time if someone already has them in an input file or TXT file, rather than PDF.
Thanks,
Bill
From: R B [mailto:slv3sat at gmail.com]
Sent: Friday, February 24, 2012 11:37 AM
To: Bishop, Bill
Cc: Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Fan energy fundamentals - Appendix G models
Was looking at it the other day - not sure if this is what you are referring to. The file is EDR_VAV_Guide_5-2-07 (too big to attach). see page 210 onwards.
On Fri, Feb 24, 2012 at 10:05 AM, Bishop, Bill <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>> wrote:
Would anyone like to share an input file (or paste the text into an email) with all the fan curves described in the EDR resource below? (Advanced Variable Air Volume VAV System Design Guide<http://www.energydesignresources.com/media/2651/EDR_DesignGuidelines_VAV.pdf>) The guide references a "New DOE-2 Fan Curves.txt" text file but I have no idea where/if I can download it. Yes, I probably could have typed it out myself by now but this gives me an excuse to post.
I offer the following curve-fit for Appendix G., Table G3.1.3.15 for any of you that don't already have it for your LEED Baseline models. (Just copy and paste into the "Performance Curves" section of the input file.):
"App G VAV Fan FPLR" = CURVE-FIT
TYPE = CUBIC
INPUT-TYPE = COEFFICIENTS
COEFFICIENTS = ( 0.0013, 0.147, 0.9506, -0.0998 )
..
Thanks,
Bill
Error! Filename not specified.<mailto:wbishop at pathfinder-ea.com>
From: Nick Caton [mailto:ncaton at smithboucher.com<mailto:ncaton at smithboucher.com>]
Sent: Tuesday, October 11, 2011 3:45 PM
To: Paul Riemer; Bishop, Bill; Dahlstrom, Aaron; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Fan energy fundamentals - Appendix G models
I've also been surprised at the magnitudes involved, but these kinds of savings do seem very real. One fundamental I had to wrap my head around (confirmed with some controls servicing contacts) is that large supply fans with VSD's should rarely operate at or near full capacity when a system is being controlled correctly.
Small differences as the curves approach zero really add up over 8760 hours however. The EDR resource linked below is really a better teacher than myself, but if you'll compare the curves I posted below, you'll notice they're actually very different at most PLR's. Actually I can overlay these pretty quickly with my personal curve spreadsheet:
Error! Filename not specified.
When looking at these: consider the same system operating at any given PLR: The difference may seem small, but at 20% PLR the system with the library curve is drawing double the energy of the 90.1 curve. Similar story but inversed around the 40% mark. Bill's model producing a ~50% difference in fan energy consumption between the curves is not outside the realm of reason considering this -his hourly PLR distribution through the year and minimum flow ratios would factor in, of course.
I more strongly do not believe these two particular curves are apples-to-apples however. My present understanding is the library VSD curve (the "Nike swoosh") represents a VSD fan system without static pressure reset (as prescribed by 90.1). The other curve shape (umm... "upturned banana?") does look like fan system curves incorporating a static reset sequence, but it's still weird that it actually approaches zero at zero (well technically 0.0013)... .
This is something I haven't reconciled with reality just yet... One thought is it would appear to represent a perfectly efficient duct system with zero static pressure to overcome at low flows - perhaps that means for a level playing field we're supposed to assume the same for a proposed curve? Is there language in 90.1/users' manual that explicitly says something along the lines of "duct/pipe distribution losses are not supposed to be modeled?"
Still mulling this over... =)
~Nick
Error! Filename not specified.
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036<tel:913.344.0036>
fax 913.345.0617<tel:913.345.0617>
www.smithboucher.com<http://www.smithboucher.com>
From: Paul Riemer [mailto:Paul.Riemer at dunhameng.com<mailto:Paul.Riemer at dunhameng.com>]
Sent: Tuesday, October 11, 2011 2:06 PM
To: 'Bishop, Bill'; Nick Caton; Dahlstrom, Aaron; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Fan energy fundamentals - Appendix G models
I agree it is not trivial but I am really surprised by that 50.8% number. I think the curves are relatively similar at the high end and most systems rarely spend time on the low end where the curves do differ considerably. Is there a big difference in the system volumes, specifically are the baseline fans bigger in volume and thus always operating at a lower ratio than the proposed?
Generally, I assume that the curve in 90.1 was supposed to represent a VAV VFD curve and that my VAV VFD fans should not be penalized against it. VAV vs. CAV is trickier and brings the temptation to switch your rationale based on which side your project falls on.
Paul Riemer, PE, LEED AP BD+C
DUNHAM
From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>]
Sent: Tuesday, October 11, 2011 1:07 PM
To: Nick Caton; Paul Riemer; Dahlstrom, Aaron; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Fan energy fundamentals - Appendix G models
Nick's concern about VAV fan curves is not trivial. I am working on a LEED model using Baseline System 5 (PVAV). The Baseline fan energy using the 90.1 G3.1.3.15 VAV FPLR curve is 50.8% more than the fan energy using the default eQUEST "Variable Speed Drive FPLR" curve. YMMV of course but that is a big difference. This penalizes the Baseline for my project - the total electrical use increases 8.9% in the Baseline vs. only a 4.1% increase in the Proposed model when switching to the same G3.1.3.15 curve.
Bill
Error! Filename not specified.
From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Nick Caton
Sent: Tuesday, October 04, 2011 3:30 PM
To: Paul Riemer; Dahlstrom, Aaron; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Fan energy fundamentals
Paul & others:
I just wanted to say off the bat: the EDR resource Paul linked us looks to address the heart of my query directly (and thank you so much!), but it's difficult for me to summarize further right now...
I think I'll need to re-read the appropriate parts of this document a few times over and arrive at a deeper understanding of actual methods/sequencing strategies for static pressure reset before I come to any definite conclusions regarding VAV fan curve.
The query I'm trying to nail down is what assumptions and specific system behaviors the DOE2 library/default curves and particularly the prescribed 90.1-2007 baseline curve represent, and from there answer what's fair game insofar as defining/modifying a different sort of EIR-FPLR curve for a proposed model. I have the understanding that the associated fan energy savings between various approaches are potentially big and real, but I'm scratching the surface of how to actually model it to a realistic degree.
If anyone has pondered the same topic or is a few strides ahead of me and wishes to share any thoughts/guidance, please do not hesitate =).
~Nick
Error! Filename not specified.
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036<tel:913.344.0036>
fax 913.345.0617<tel:913.345.0617>
www.smithboucher.com<http://www.smithboucher.com>
From: Paul Riemer [mailto:Paul.Riemer at dunhameng.com<mailto:Paul.Riemer at dunhameng.com>]
Sent: Friday, September 30, 2011 7:21 AM
To: 'Dahlstrom, Aaron'; Nick Caton; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: RE: [Equest-users] Fan energy fundamentals
As for fans I suggest two resources:
Advanced Variable Air Volume VAV System Design Guide<http://www.energydesignresources.com/media/2651/EDR_DesignGuidelines_VAV.pdf> by Energy Design Resources has some good discussion and suggested fan curves.
Reid Hart of PECI did a presentation to BSUG on September 16, 2009 on fan curves and static pressure reset. BSUG posted their items, including this one, to their yahoo group at http://tech.groups.yahoo.com/group/BSUG/files/. BSUG has morphed into BESF and has a new home at http://energytrust.org/business/building-energy-simulation/.
Paul Riemer, PE, LEED AP BD+C
DUNHAM
From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Dahlstrom, Aaron
Sent: Friday, September 30, 2011 12:03 AM
To: Nick Caton; Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Fan energy fundamentals
Nick -
We're in the midst of asking the same questions about the Pump-Power-fFlow equations.
I imagine in both types of flow networks there may some fixed pressure drops that won't be reduced:
1) Min static pressure across flow control devices (VAV boxes, water control valves)
2) Static pressure in critical branches that may not be at reduced flow, even though the overall flow network is at reduced flow
3) In staged plants, static pressure across individual constant-volume plant components (eg in our case, chiller 1 of 6 always has 12 psig, regardless of whether it is the only chiller on or not)
With this mixture of fixed and variable pressure drops, I imagine multiple different power-versus-flow curves for the same building, depending on the physical location of the prime movers and the intervening pinch points / critical flow networks. 20000 cfm out of a peak 30000 cfm fan probably looks different in terms of power depending whether the majority is headed to west zones from an east mechanical room 400 ft away or headed to east zones just a few feet away.
Probably the most accurate method would be explicitly defining the flow network and calculating these pressure drops dynamically (if the modeler had the time to do that explicitly, or software cool enough (BIM?) to do it automatically). Anyone familiar enough with Energy Plus to know if that's a feature?
I guess no answers here, just more questions ...
Aaron Dahlstrom , PE, LEED(r) AP
In Posse - A subsidiary of AKF| 1500 Walnut Street, Suite 1414, Philadelphia, PA 19102
d: 215-282-6753<tel:215-282-6753>| m: 267-507-5470<tel:267-507-5470>| In Posse: 215-282-6800<tel:215-282-6800>| AKF: 215-735-7290<tel:215-735-7290>
e: ADahlstrom at in-posse.com<mailto:ADahlstrom at in-posse.com> | in posse web: www.in-posse.com<http://www.in-posse.com/> | akf web: www.akfgroup.com<http://www.akfgroup.com/>
From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Nick Caton
Sent: Thursday, September 29, 2011 12:08 PM
To: Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Fan energy fundamentals
Bill Bishop suggested a good clarification that I want to take on. I've edited my language below (highlighted) to clarify the question I'm trying to pose.
~Nick
From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org]<mailto:[mailto:equest-users-bounces at lists.onebuilding.org]> On Behalf Of Nick Caton
Sent: Thursday, September 29, 2011 10:32 AM
To: Equest-users at lists.onebuilding.org<mailto:Equest-users at lists.onebuilding.org>
Subject: [Equest-users] Fan energy fundamentals
Hi everyone!
A recent discussion with a mechanical mentor brought up a question I'd like to share with the list... If anyone has a partial or complete response I think we'd all benefit and appreciate it if you'd share your thoughts!
For a given duct distribution system, you've got a certain static drop. At full flow, your supply fan also has to deal with a certain velocity pressure drop due to friction with the duct distribution. If you reduce the supply airflow rate, you also lower the velocity and therefore the velocity pressure drops for the given duct distribution. The net result is system supply fan has a lower total pressure drop to overcome, and so should operate more efficiently.
Does anyone know: Whether we choose "variable speed" fan control, use the FAN-EIR-FPLR curve generated by the wizards, or use the VSD curve defined in 90.1 appendix G... are we simultaneously accounting for the efficiency gains due to lowered velocity pressure drop in addition to the drop in fan energy from lower RPMs? If this is not accounted for inside/outside the fan curves, is there a direct way to define that or logically work it into the curves?
If it helps anyone answer, I can illustrate from recent checks that the wizard-generated FAN-EIR-FPLR curve has a "Nike Swoosh" shape with an inflection around the 20% mark. This shape best matches the (limited) data I've seen for "real world" VSD input measurements. Here's a screenshot:
Error! Filename not specified.
The following illustrates the 90.1-2007 VAV curve we're made to use for baseline systems 5-8 (I haven't checked to see if this still applies to 2010). It does not have the same "inflection point" as zero is approached. I think it's based on the fan law power equation or something similar that doesn't account for motor/VSD losses:
Error! Filename not specified.
The help files illustrate a different, third shape for "variable speed" control different from both of the above...
Error! Filename not specified.
Seeing these side-by-side raises another question for me regarding 90.1-2007 intent/practice... not specific to eQuest... but I've already spent too much of my time today writing this out! Another day =)...
Thanks in advance for anyone joining in the discussion!
~Nick
Error! Filename not specified.
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036<tel:913.344.0036>
fax 913.345.0617<tel:913.345.0617>
www.smithboucher.com<http://www.smithboucher.com>
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Subject: Re: [Equest-users] Fan energy fundamentals - Appendix G models
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