[Equest-users] Constructing chiller part load curves

[Carol Gardner]

Hi all,

I agree with all the strategies listed in these emails. HOWEVER, please do
not pass by the article I attached again today, and will attach to this
also.

This article was not written by me but rather by Steve Gates, the same guy
that writes and maintains the HVAC portion of eQUEST. I was working with a
client on chiller curves when the original Chiller Curves (Oh Boy!), thanks
Nick, chain of emails began. There was something about the EDR article that
bothered me and I talked to Steve about it. Steve, being nothing if not
thorough, read the article and wrote the new article with some amendments
and additions.

This article, the contents of the DOE2 Manuals and the EDR article should
provide you with everything you need to create chiller curves. I would
suggest reading all of them starting with everything in the DOE2 Manuals,
moving on the the EDR article and finishing with the Chiller Curves SDG,
etc., as it is, more or less, the final word.

Best,

Carol

On Wed, Jan 19, 2011 at 9:00 AM, Nick Caton <ncaton at smithboucher.com> wrote:

>  Hi Afaan,
>
>
>
> The first table below contains the *sort* of information you will need to
> make a centrifugal EIR curve, but as David says you’re lacking in the
> minimum # of data points.  I believe the bare minimum to extrapolate an
> accurate bi-quadratic curve would require 9 rows of data (minimum 3 PLR’s
> for a minimum 3 dT’s), though you should probably use the maximum number of
> data entry points permitted when allowing eQuest to determine the
> coefficients (20 per curve).
>
>
>
> dT is simply the difference between the chilled and condenser water temps.
>
>
>
> I’m not sure exactly what we’re looking at in the second table, but it
> doesn’t look like data for creating a curve...  If you want to make CAP-FT
> and EIR-FT curves (and if you don’t, that’s okay too – see below) you’ll
> need a rep who understands and can provide you with “maximum capacity” (not
> the designed capacity, or where PLR = 1.0) and power drawn under different
> conditions.  I’ve previously selected 5 CW temps and 4 CHW temps around and
> including the design conditions being normalized to, totaling the maximum 20
> data entry points we’re permitted to input.
>
>
>
> The attached email contains an overview of materials you should review to
> understand the process of custom chiller curve creation (includes a
> reference to the same EDR guideline David brings up below).  Once you feel
> comfortable understanding the required data collection described towards the
> end of the referenced EDR chapter, you might do well to also read through a
> fairly lengthy discussion on this list that I started:  “Chiller Curves
> (oh boy!).”   There, I eventually provided an illustrated breakdown of
> each default curve and its function/implications, eventually realizing and
> providing visuals of their combined effects analogous to what equipment reps
> often provide for “chiller efficiency curves.”  You should be able to follow
> this discussion from start to finish, and should come away knowing exactly
> what eQuest is doing “under the hood” moving forward.  Carol Gardner also
> provided a writeup within that discussion that is similar to the EDR… oh I
> see she just posted it again =)!
>
>
>
> One final suggestion:  Your collected data suggests a possible pitfall – if
> you want to make the CAP-FT and EIR-FT curves, you MUST gather data for
> multiple CHW temps, even if the design should only ever call for 44 degree
> water to be produced.  If you don’t understand why, then honestly you need
> further review of what the curves are functionally doing – see suggested
> reading above and attached.
>
>
>
> If you and your reps are struggling with producing the data required to
> make CAP-FT and EIR-FT curves, it’s advisable to stick with the defaults,
> and ensure your custom EIR-fPLR&dT curve entries are all normalized to ARI
> rather than a design condition.
>
>
>
> Best of luck!
>
>
>
> ~Nick
>
>
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
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>
> www.smithboucher.com* *
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *David Eldridge
> *Sent:* Wednesday, January 19, 2011 7:38 AM
>
> *To:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Constructing chiller part load curves
>
>
>
> You may want to run through this document before you get too much further.
> Skip ahead to “Part 2” of the document.
>
>
>
>
> http://www.energydesignresources.com/media/2654/EDR_DesignGuidelines_%20HVAC_Simulation.pdf
>
>
>
> In a nutshell – you should acquire a few more data points to develop a more
> comprehensive matrix.  Right now your matrix would be equivalent to a line
> through the middle of possible conditions, you need to extend your data set
> over a wider range of water temperatures and load conditions.
>
>
>
> David
>
>
>
> *
> *
>
>
>
> *David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, HBDP*
>
> Project Manager
>
>
>
> Direct: (847) 316-9224 | Fax: (847) 328-4550
>
> http://www.grummanbutkus.com
>
>
>
> *Grumman/Butkus Associates* | 820 Davis Street, Suite 300 | Evanston, IL
> 60201
>
> Energy Efficiency Consultants and Sustainable Design Engineers
>
> *
> *
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Afaan Naqvi
> *Sent:* Tuesday, January 18, 2011 8:33 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Constructing chiller part load curves
>
>
>
> After browsing the forums, it seems there are many users that have
> constructed custom chiller curves based on selection data. I believe I have
> all the data I need to do this, but am coming up with polynomial
> coefficients and hourly results that do not make sense at all. Can someone
> please walk me through how to go about building the 3 curves for a
> centrifugal, water cooled chiller with a VSD based on the following data:
>
>
>
> % Load
>
> Capacity
>
> kW in
>
> Perf
>
> Evap T in
>
> Evap T out
>
> Conden T in
>
> Coned T out
>
> 100
>
> 85
>
> 53.6
>
> 0.63
>
> 54
>
> 44
>
> 85
>
> 94.8
>
> 75
>
> 63.8
>
> 29.8
>
> 0.47
>
> 51.5
>
> 44
>
> 75
>
> 82
>
> 50
>
> 42.5
>
> 13.3
>
> 0.31
>
> 49
>
> 44
>
> 65
>
> 69.5
>
> 25
>
> 21.3
>
> 6.9
>
> 0.32
>
> 46.5
>
> 44
>
> 65
>
> 67.2
>
>
>
>
>
> I believe the additional data I need is calculated below, except for the dT
> term which I am unclear on:
>
>
>
> Load
>
> PLR
>
> kW
>
> f PLR
>
> 85
>
> 1
>
> 53.6
>
> 1
>
> 63.8
>
> 0.751
>
> 29.8
>
> 0.556
>
> 42.5
>
> 0.500
>
> 13.3
>
> 0.248
>
> 21.3
>
> 0.251
>
> 6.9
>
> 0.129
>
>
>
>
>
> Not sure if the dT term required by the curves is the difference in
> condenser supply and return, or condenser and evaporator supply, condenser
> supply and evaporator return, etc. Can someone please clarify?
>
>
>
> Thanks
>
>
>
>
>
> *Afaan Naqvi ** *PE  LEED AP
>
> ____________________________________________________________
> Electronic mail messages entering and leaving Arup  business
> systems are scanned for acceptability of content and viruses
>
>
> ---------- Forwarded message ----------
> From: "Nick Caton" <ncaton at smithboucher.com>
> To: "Grammy" <grammy.hkust at gmail.com>, "Ana N." <ananeddav at hotmail.com>
> Date: Fri, 5 Nov 2010 09:12:24 -0600
> Subject: Re: [Equest-users] Electricity consumption by CHILLER
>
> Ana/Grammy:
>
>
>
> Chiller modeling is a topic that took me many attempts (projects) to fully
> get my arms around, so don’t get discouraged if it boggles the mind.
>
>
>
> To start, remember that the reported “space cooling” end use consumption
> values may include energy from components other than your chiller (heat
> pumps, DX cooling…), so make sure that’s not clouding your perspective.
>
>
>
> With that out of the way, you’re right to first check and ensure the loads
> on the loop are appropriate to what you’re trying to model.  I think you
> should review what CAPhour and PLR really represent…  Multiplying them
> should result in your hourly load, in Btuh, but if you’re multiplying your “operating
> chiller capacity at current condition” (Hourly Load) by your PLR then I
> suspect the result would be equal to “PLR^2/CAPhour.”  I’m doubtful that’s
> the value you were looking for… Let me suggest two paths to account for what
> you’re trying to do:
>
>
>
> *If you are working with the library performance curves*, recognize you
> have a limited number of critical inputs to review/edit regarding the
> behavior of the chiller itself:  Capacity (a part of CAPhour) and EIR at
> the design/rated conditions, the design conditions themselves, and the
> associated loop temperatures.  If any input on the chiller screens is
> something you’re unsure of, right-click it and read/re-read the associated
> help entry.
>
>
>
> *If you want to delve into custom performance curves*, welcome to the
> rabbit hole!  This required significant personal learning and time for me to
> get my arms around, I would suggest expecting the same.  I’d suggest first
> getting comfortable specifying chillers using the library curves, per above
> before pursuing this skillset.
>
> Still here?  Okay, the following 3-step program is what I wish I could go
> back in time and tell myself months ago:
>
> 1.       Open the DOE2 help files to Volume 2: Dictionary > HVAC
> Components > Chiller.  Read everything in the tree in order up to the
> “Attachment to Chilled Water Loop” entry, and stop.  Pay special attention
> to the “Chiller Energy Consumption” article and the sub-entries describing
> each performance curve in that equation.  When you’re familiar enough to
> recount all the variables involved in that equation you brought up below by
> memory, proceed to…
>
> 2.       Download the EDR design guidelines to HVAC simulation<http://www.energydesignresources.com/Portals/0/documents/DesignGuidelines/EDR_DesignGuidelines_%20HVAC_Simulation.pdf>,
> and read the chapter on chillers, pages 23-44 (of 65).
>
> a.       Re-read until you feel comfortable understanding what information
> you need from your manufacturer rep/vendor.  A good rep is always trying to
> be helpful, and may unintentionally provide the wrong information and
> convince you both you’re on solid footing.  You must know exactly what data
> you do and don’t need before beginning the discussion of asking for that
> information.  Whether your vendor/rep can deliver exactly what you want is
> something of a toss-up, but it’s a pretty slim chance if you don’t know what
> that is yourself.
>
> b.      The equations presented showing the math behind the coefficients
> may seem insurmountable, but for context recognize the author(s) of this
> document advocating to not figure out the coefficients directly… rather to
> let eQuest/DOE2 do that legwork for you (the “data method”).  To an extent
> this is something of a reference regarding what’s going on “under the hood.”
>
> 3.       Read the lengthy discussion I started this week (with
> illustrations) under the heading “Chiller Curves (oh boy!).”  This hopefully
> also bring you full circle to understanding what the default curves really
> look like, what they each individually represent, and ultimately how they
> work together.  Note my discussion revolved around a centrifugal VSD
> chiller, for context.  Other equipment may use curves of a simpler format.
>
>
>
> *If a “bi-quadratic equation” sounds like something that makes the warp
> drives work on the Star Ship Enterprise, stop for a second and review the
> math – it’s not that crazy.  You might want to skip ahead to see to those
> visualizations I provided, or even build your own in excel.
>
>
>
> Best of luck!
>
>
>
> ~Nick
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, E.I.T.***
>
> PROJECT ENGINEER
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> *Check out our new web-site @ *www.smithboucher.com* *
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Grammy
> *Sent:* Friday, November 05, 2010 6:17 AM
> *To:* Ana N.
> *Cc:* equest-users
> *Subject:* Re: [Equest-users] Electricity consumption by CHILLER
>
>
>
> I am also confusing this problem, and I strongly recommend you to read the
> DOE-2 engineering manual, verison 2.1A, and DOE-2.2 volume 4, which can be
> downloaded from eQuest web site.
>
>
>
> On page V.35 - V.38, engineering manual, it introduces the electric
> calculation of chiller, and on page 265, volume4, it introduces the chiller
> variable list number, you can export the hourly data in eQuest and
> calculated by hand. I am lost at this step. As i know at this place, there
> is something you need to notice, the unit of assign loading (1) shall be
> BTU, and electric demand (12) may be kW, then I still can't get the right
> number, if you get it, please let me know how.
>
>
>
> On Fri, Nov 5, 2010 at 8:04 AM, Ana N. <ananeddav at hotmail.com> wrote:
>
>
> I am trying to calculate/estimate the electricity consumption by a
> chiller based on hourly outputs.
>
> First, I plugged the cooling coil load on loop and corrected EIR in the the
> equitation
>  Elec= CAP hour* EIR*EIR(t1,t2)*EIR(PLR,dT)/3413 Btu/kW
>
> but the calculated annual electricity consumption was not  even close to
> the numbers reported under Space Cooling Enduse.
>
> Then, I used PLR and operating chiller capacity at current condition to
> calculate CAP hour (instead of using the cooling coil load on loop), but
> calculated numbers did not make any sense.
>
> Has anyone done similar calculations? I am sure I am missing something very
> simple here, but what?
>
> Any suggestions are very appreciated
>
>
> Ana
>
>
>
>
>
>
>
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-- 
Carol Gardner PE
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