[Equest-users] IPLV Curve Fit

[Robby Oylear]

Page 33 of the design guide linked below is what I've used to determine that
EIRFPLR is based on kW power draw and not EIR ratio's.

EIRFPLR = Pi / (Pref * CAPFTi * EIRFTi)

Where:
Pi = part-load input power
Pref = full-load input power at the same evaporator and condenser
temperature
CAPFTi = correction factor for capacity as a function of temperature (assume
= 1 for constant temperature part-load rating)
EIRFTi = correction factor for efficiency as a function of temperature
(assume = 1 for constant temperature part-load rating)

I've assumed CAPFT and EIRFT are equal to one since the effects of
temperature on capacity efficiency are handled by the Cap-fCHWT&DBT and
EIR-fCHWT&DBT curves.

-Robby

On Fri, Jun 17, 2011 at 6:30 AM, Paul Diglio <paul.diglio at sbcglobal.net>wrote:

> Lyle:
>
> The link below has a great section on creating DOE2 chiller curves.
>
>
> http://www.energydesignresources.com/resources/publications/design-guidelines/design-guidelines-hvac-simulation-guidelines.aspx
>
> Paul Diglio
> ------------------------------
> *From:* Lyle Keck <lkeck at aeieng.com>
> *To:* Carol Gardner <cmg750 at gmail.com>; Nick Caton <
> ncaton at smithboucher.com>
> *Cc:* "equest-users at lists.onebuilding.org" <
> equest-users at lists.onebuilding.org>
> *Sent:* Thu, June 16, 2011 4:46:09 PM
> *Subject:* Re: [Equest-users] IPLV Curve Fit
>
> Robby, Nick, and Carol,
>
>
>
> Thanks for all of the input regarding this issue.  I am working on
> obtaining some temperature specific data from the manufacturer.
>
>
>
> I understand this is one of the more complicated procedures to tackle, but
> I hope revisiting this issue will benefit all of the archive users.
>
>
>
>
>
> *Lyle Keck**  *
> SustainablE Systems Analyst
>
>
>
> *AEI* | AFFILIATED ENGINEERS, INC.
> Westlake Center Office Tower, 1601 Fifth Avenue, Suite 1400 | Seattle, WA
>  98101
>
> P: 206.256.0800 | F: 206.256.0423
> lkeck at aeieng.com  |  *www.aeieng.com*
>
>
>
>
>
>
>
>
>
>
>
> *From:* Carol Gardner [mailto:cmg750 at gmail.com]
> *Sent:* Wednesday, June 15, 2011 9:44 PM
> *To:* Nick Caton
> *Cc:* Robby Oylear; equest-users at lists.onebuilding.org; Lyle Keck
> *Subject:* Re: [Equest-users] IPLV Curve Fit
>
>
>
> Hi All,
>
> For curve-fitting I always refer to these two sections of the DOE2
> documentation, attached. Until I spent some time with the equations I really
> didn't get what the program was doing with curve information. Studying them
> is never a waste of time. The second one shows how to create a curve using
> "raw data", which IS normalized around the ARI design point. I use raw data
> because I have always been able to get it from equipment reps: just ask for
> the Technical Specifications. I have never had a vendor offer up curve
> coefficients. Once you enter your raw data eQUEST will calc the curve
> coefficients with it. Anyway, it's tedious and you need to be careful but if
> you have any kind of whoop di do equipment you are using it will be worth
> the effort as the curves within eQUEST only get updated when there's a new
> release, if then.
>
> I also distributed all the equations need for the new VFD chillers around
> the time of Chiller curves, oh my, and I believe Jeremy McClanathan
> distributed a spreadsheet that went with it. Something we should all thank
> him for.
>
> Cheers,
>
> Carol
>
> On Wed, Jun 15, 2011 at 4:46 PM, Nick Caton <ncaton at smithboucher.com>
> wrote:
>
> Hi Robby!
>
>
>
> Let me back into this with some clarifications for everyone’s benefit – I
> might be learning something here too!
>
>
>
> First, the procedure I’m describing below is specifically to guide someone
> in developing an EIR-fPLR, not an EIR-fPLR& dT curve.  In that point, you
> and I diverged in how we’re advising Lyle to proceed.  The discussion I
> attached previously delves into whether one curve type or another is
> appropriate for a given situation… but to summarize a long discussion: a
> curve incorporating dT is not always critical to modeling behavior in line
> with the actual equipment.
>
>
>
> Second, below I’ve copied a library EIR-fPLR curve per your suggestion, and
> I’ve generated a visualization as well for discussion:
>
>
>
> [Inserted picture: eQuest library curve input screen illustrating curve
> coefficients for an EIR-fPLR curve]
>
> [Inserted picture: Excel plot of that library curve’s coefficients]
>
> (x-axis is the PLR, y-axis is the “EIR factor”)
>
>
>
> I think we all agree, but let’s collectively be clear on this point:  This
> curve does *not* represent “efficiency.”  It is a factor applied against
> the EIR specified for the chiller at full load.  As we can observe, the EIR
> “correction factor” decreases as part load decreases, and that agrees with
> our expectation that the chiller should draw less energy per unit work (or
> be “more efficient”) at part load.
>
>
>
> Efficiency is “what you get out / what you put in,” where measures like
> kW/ton and EIR are conceptually more of an inverse: “what you put in / what
> you get out.”
>
>
>
> I took a look at the linked discussion Robby, and while I was not privy to
> the off-list discussion, I sense we may have a different understanding here
> (or we might concur?)… Does all this sit agreeably with you to this point?
> If anything I’m stating seems incorrect, I (and others) would very much
> appreciate being corrected, preferably with illustrations ^_^!
>
>
>
> Our syntax might be getting in the way... so let me touch on that as well:
> When I say this library curve is “normalized,” it is because the derived
> equation returns a correction factor, not an actual EIR figure.  The library
> curve above is telling us that at 100% loading, the EIR should be 1.00 x
> [specified EIR at 100%].  If you were build a curve as I describe below
> without first dividing the EIR data points by the 100% figure (so the factor
> at 100% is 1.0), you will have coefficients that will produce actual EIR’s
> for any given PLR, which would be multiplied for each hour against the
> specified EIR… The results could either be wildly off from reality, or could
> also produce deceptively sensible behavior as well.  I suppose a curve
> created this way might be made to work correctly if you make a point to
> specify the chiller’s EIR as 1, but I’m not entirely sure something else
> wouldn’t be affected… =)
>
>
>
> I do want to support that Robby is correct to assert one cannot build a
> performance curve from an IPLV rating alone, but one can work towards a
> simple fPLR curve if that’s desirable and appropriate for the model at hand,
> if you do have the values for each part load point as Lyle is describing
> (you cannot extrapolate these from the IPLV number).
>
>
>
> A few extra points: I forgot to mention is that EIR-fPLR curves can be
> entered as either Quadratic (2nd order) or Cubic (3rd order), so in excel
> it would be a good exercise to try out both with your curve-fit and see what
> shape fits your data/expectations best.  Also, I may have somewhat
> overstated the importance of specifying a chiller at ARI conditions when
> using EIR-fPLR curves… but suffice to say – the library curves are built
> around ARI conditions, so specifying your chiller at ARI conditions is
> always a safe bet if you aren’t planning to make a full set of curves around
> your design conditions.
>
>
>
> Game on!
>
>
>
> ~Nick
>
> [image: 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:* Robby Oylear [mailto:robbyoylear at gmail.com]
> *Sent:* Wednesday, June 15, 2011 4:36 PM
> *To:* Nick Caton
> *Cc:* Lyle Keck; equest-users at lists.onebuilding.org
>
>
> *Subject:* Re: [Equest-users] IPLV Curve Fit
>
>
>
> Hi Nick,
>
>
>
> In my experience the EIRFLPR curve is not looking for a normalized
> efficiency.  If you look at the default chiller curves you'll notice that
> the EIRFPLR correction factor actually decreases as you approach zero
> part-load.  This would not make sense if it was an EIR correction factor, as
> the efficiency of the chiller actually increases as part-load decreases (at
> least with a variable speed chiller).
>
>
>
> The chiller EIRFPLR curve is actually looking for a ratio of current kW
> power draw divided by kW power draw at full-load.
>
>
>
> The thread from when I was struggling through this for the first time
> myself is located here:
> http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2008-February/006827.html
>
>
>
> Not all that useful as I believe someone assisted me through the process
> off-list, but the conclusion remains the same.
>
>
>
> -Robby
>
> On Wed, Jun 15, 2011 at 1:55 PM, Nick Caton <ncaton at smithboucher.com>
> wrote:
>
> Hi Lyle,
>
>
>
> I think you need to review a little further before proceeding.  Read
> through the attached discussion from the bottom up.  This discussion
> diverges a bit (as performance curve topics usually do) but I think you’re a
> bit ahead of the curve so to speak (har har!) in recognizing what the IPLV
> numbers really mean.  Plugging in your IPLV values as coefficients for a
> cubic equation (where f(x) = Ax^3+Bx^2+Cx+D) is pretty much wildly different
> from the correct course of action, but you’re definitely in the ballpark’s
> parking lot ;).
>
>
>
> Ultimately, you (and others – listen up!) will probably have the best shot
> of getting it right on the first go if you visualize what you’re doing in
> excel.  That’s what worked for me when I was climbing this mountain:
>
>
>
> ·         Assemble your part load percentages and corresponding EER’s in
> excel
>
> ·         Stop and review what the curve in eQuest is looking up, and from
> what variable(s).  You can glean this from the title of the default curve
> used…  In this case, you want eQuest to determine EIR each hour as a
> function of Part load (EIRfPLR).
>
> ·         Knowing that, convert convert your EER values to to EIR
>
> ·         Now, normalize each EIR value to the ARI value*.  If the EER at
> ARI is 9, and your 50% part load EER is 6, then the normalized vaule is 6/9
> = 0.67.  This normalized number is actually a multiplier of sorts that
> eQuest will apply against your specified ARI efficiency in the chiller input
> window.  If none of this is making sense, go back further and review my
> “recommended reading” list in a thread called “Chiller curves, oh boy!” from
> sometime last year in the archives.
>
> ·         Using excel, plot these normalized efficiencies (y-axis) against
> the part load ratios (x-axis) with a scatter chart.
>
> ·         Right click and add a curve-fit to the series.  In the dialog,
> try making it third order (quadratic) and see if you get a good fit.  Check
> the option to display the curve equation.
>
> ·         Voila, there are your four coefficients (A,B,C,D – see eQuest’s
> curve inputs to be sure you know which is which in the quadratic format) for
> eQuest!  You’ve also developed a visual check to ensure the numbers make
> sense.
>
>
>
> *Important:  You MUST work from ARI-condition data points, and normalize to
> the ARI condition, and specify your chiller’s capacity/efficiency at ARI
> conditions, if you are trying to only make PLR curves without doing a full
> set of custom curves.  The reasons why are complex, and I’ve already nearly
> written a book on the matter in the archives if you’re itching to know why
> ^_^.  If you want to specify your chiller around design conditions, then
> it’s all or nothing (library curves) with regard to custom curve creation!
>
>
>
> A general statement/consolation to everyone: We all have to crawl before we
> can run!  Make no mistake, coming to a true fundamental understanding of
> custom curves in eQuest/DOE2, to the point you can manipulate and even
> create them on your own, is no small feat.  They should give out medals!
> The best way to develop this skill set is to accept you will probably screw
> it up a few times to start, look hard at your results, and read up on the
> literature/advice that’s out there in order to learn what it is that you
> personally don’t know.  Once you come around to understanding what you do
> know, and more importantly what you know that you don’t know… (Donald
> Rumsfeld would make a good energy modeler, lol<http://en.wikiquote.org/wiki/Donald_Rumsfeld>),
>  it’s all downhill from there, and you can begin to ask the right questions
> of yourself and others to bridge your personal gaps.  Making mistakes is
> commendable, provided you resolve to learn from them!
>
>
>
> ~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
>
> fax 913.345.0617
>
> www.smithboucher.com* *
>
>
>
>
>
> *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
>
> 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 *Robby Oylear
> *Sent:* Wednesday, June 15, 2011 2:43 PM
> *To:* Lyle Keck
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] IPLV Curve Fit
>
>
>
> Lyle,
>
>
>
> The short answer is no.  IPLV cannot be used to create performance curves
> in eQUEST.
>
>
>
> Part-load curves are a strange animal in eQUEST. You'll need cooperation
> from the chiller manufacturer to get the correct data.  You need to have
> enough data to describe the way energy varies as a function of part-load,
> chilled water supply temp, and outside air temperature.  Take a look at the
> attached spreadsheet which can be used to create curves in eQUEST.  The data
> in yellow should be entered by the manufacturer or manufacturer's rep. The
> data in red should be entered into eQUEST.
>
>
>
> If you look into the formulas, you'll note that EIR-FPLR is actually not an
> EIR factor, it is based on the power draw of the equipment at part-load
> compared to at full-load.  This throws a lot of people off as it is not
> described that way in the help documentation.
>
>
>
> The interesting question that arises when working with custom part-load
> curves is how accurate does the eQUEST default performance curve model the
> required IPLV for the baseline per ASHRAE 90.1?  In my experience the
> default curve is approximately 10% worse than the IPLV requirement.
>
>
>
> Hope this helps,
>
>
>
> Robby Oylear, LEED AP BD+C
>
> Mechanical Project Engineer
>
> Energy Analyst
>
> Rushing
>
>
>
> On Wed, Jun 15, 2011 at 10:59 AM, Lyle Keck <lkeck at aeieng.com> wrote:
>
> All,
>
> I am trying to create a part load curve for an air-cooled screw chiller.  I
> have the EER & COP data for 100%, 75%, 50%, and 25% loading.
>
>
>
> I have read through the various posts in the archives and I am still unsure
> if I should input this data as ‘raw data’ or ‘coefficients’
>
>
>
> From previous posts:
>
>
>
> IPLV (or NPLV) = 0.01A+0.42B+0.45C+0.12D
>
> Where:
>
> A = COP or EER @ 100% Load
>
> B = COP or EER @ 75% Load
>
> C = COP or EER @ 50% Load
>
> D = COP or EER @ 25% Load
>
>
>
> It is my understanding that EIR-PLR curves give the EIR as a function of
> part load ratio.
>
>
>
> SO, if I create a ‘cubic’ curve with input type ‘curve coefficients’, and
> input a=(1/COP-100%), b=(1/COP-75%), c=(1/COP-50%), and d=(1/COP-25%) and
> specify this curve as the EIR - f(part load ratio) curve, would that be
> accurate?
>
>
>
> Additionally, this chiller has a condenser water temp of 95 degF and design
> conditions that differ from AHRI conditions (design EWT=58 degF and LWT=44
> degF)
>
> Do these values have direct correlation to the curve creation ? Or can the
> condenser and CHW temp simply be defined in the ‘basic specifications’ tab
> for the chiller, and the EWT defined via the CHW loop deltaT?
>
>
>
> I know this topic has been widely discussed, but I am still uneasy about
> the actual inputs for the creation of the part load performance curve.
>
>
>
> Any input, or reference to a previous post would be appreciated.
>
>
>
> Thanks in advance,
>
>
>
> *Lyle Keck**  *
> SustainablE Systems Analyst
>
>
>
> *AEI* | AFFILIATED ENGINEERS, INC.
> Westlake Center Office Tower, 1601 Fifth Avenue, Suite 1400 | Seattle, WA
>  98101
>
> P: 206.256.0800 | F: 206.256.0423
> lkeck at aeieng.com  |  *www.aeieng.com*
>
>
>
>
>
>
> _______________________________________________
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> http://lists.onebuilding.org/listinfo.cgi/equest-users-onebuilding.org
> To unsubscribe from this mailing list send  a blank message to
> EQUEST-USERS-UNSUBSCRIBE at ONEBUILDING.ORG
>
>
>
>
>
> ---------- Forwarded message ----------
> From: "Paul Diglio" <paul.diglio at sbcglobal.net>
> To: "Nick Caton" <ncaton at smithboucher.com>, <
> equest-users at lists.onebuilding.org>
> Date: Sat, 26 Feb 2011 07:15:46 -0500
> Subject: Re: [Equest-users] using IPLV in eQuest
>
> Nick:
>
> I agree with your analysis.  A curve built using different kW/Ton for the
> four different load ratios that are used in the IPLV calculation would be
> sufficient.
>
> I would just be careful when creating a curve that uses different condenser
> water supply temperatures.  It is more of a design issue.  There has to be a
> reason why the condenser water temperature varies.  It will effect the lift
> and kW/Ton.  For example, current chillers will tolerate a much lower
> condenser water temperature.  Does this mean that it is more efficient to
> provide the lower condenser water temperature?  Not necessarily, since
> energy will be wasted running the cooling tower fans to achieve the lower
> temperature and energy will be wasted for the hot-gas bypass to bring the
> condenser pressure up.
>
> In my experience, the lower condenser water temperature is most often an
> issue on chiller start-up in cold weather.  Some chillers will surge until
> the chiller warms the condenser water loop.  Surging sounds like someone
> with advanced COPD breathing.
>
> So, if Rohini's chillers are supplied with a nearly constant condenser
> water temperature, the EIR f(PLR&Lift) would not be critical.
>
> Please see attached modeling data from Trane for a CVHE 450 ton chiller.
> All the data to build the various curves is shown.  Note the difference in
> condenser bundle pressure drop for standard flow v. minimum flow.  Much
> energy can be saved with a variable condenser water pumping strategy.
>
> This data was used to calculate the loss of chiller efficiency due to
> reduced condenser water flow.  In this particular project, I had three
> existing chillers.  Total savings realized by the variable condenser water
> scenario was 250,000 kWh/Year.  The reduced chiller efficiency consumed
> 50,000 kWk per year so the net energy savings was 200,000 kWh/Year.  Notice
> that the condenser water temperature varies in the data.  That was based on
> the maximum heat rejection of the towers during the cooling season with a
> minimum of 65 degrees condenser water supply temperature.  If I assumed a
> constant 78 degrees condenser water supply temperature the kW/Ton values
> would be much different.
>
> It takes a little time to find the right person to provide this chiller
> data, but it is well worth it.
>
> Paul
>
>
>
>
> ------------------------------
>
> *From:* Nick Caton <ncaton at smithboucher.com>
> *To:* Paul Diglio <paul.diglio at sbcglobal.net>;
> equest-users at lists.onebuilding.org
> *Sent:* Fri, February 25, 2011 4:38:43 PM
> *Subject:* RE: [Equest-users] using IPLV in eQuest
>
> Thanks very much for the informed response, Paul!
>
>
>
> With all respect, I want to be sure I’m picking up the right lessons here
> =):
>
>
>
> Accepting the arbitrary nature of IPLV ratings, what I’ve proposed for
> Rohini’s case is to define a curve that will utilize his model’s unique
> annual part-load profile (tossing IPLV’s weightings out the window), and
> would isolate the effects of PLR to make his equipment comparison.
>
>
>
> Am I correctly understanding that any comparative analysis that isolates
> only the effects of part-load in comparing two chillers is pretty much
> pointless?
>
>
>
> I am not trying to make a case that lift, variable flows, and their effects
> on capacity and efficiency are not important (and I have also experienced
> responses all over the map from different manufacturers).  I agree that at
> least considering all of these in many cases is necessary when one wants to
> model accurate behavior, particularly from a commissioning/servicing
> context.  With all other things being equal, I’m however proposing these
> factors shouldn’t be critical if the specific goal is to determine *whether
> chiller A or chiller B fits a model’s part load profile better*.
>
>
>
> So to clarify and make our bridges meet:  Is it critical that Rohini
> creates an EIR-fPLR&dT curve for his analysis (between two screw chillers
> with everything else presumed identical), or is it fair to say this may be
> overkill considering what he’s trying to achieve?
>
>
>
> I for one will continue the good fight to obtain more solid input data for
> my curves, sometimes I have to settle for “the best I can get” with the
> people I’m supposed to be talking to, but your experiences are further
> motivation to try to find the right people =)!
>
>
>
> Thanks again,
>
>
>
> ~Nick
>
>
>
> *Error! Filename not specified.*
>
> * *
>
> *NICK CATON, E.I.T.*
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> www.smithboucher.com* *
>
>
>
> *From:* Paul Diglio [mailto:paul.diglio at sbcglobal.net]
> *Sent:* Friday, February 25, 2011 2:58 PM
> *To:* Nick Caton; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] using IPLV in eQuest
>
>
>
> Nick:
>
> I come from a mechanical contracting and service background.  Condenser
> water temperature is a hotly debated item.  Some manufacturers define a very
> narrow range of acceptable condenser water temperature and others define a
> very narrow range of the temperature difference between entering and leaving
> condenser water temperature.
>
> During one investment-grade audit I performed recently, Trane told me that
> the condenser water dt can be no *less* than 5 degrees for maximum
> efficiency on the 650 ton CVHE chillers I was working with.  The water
> temperature could be anywhere to 50-80 degrees.  This machine had hot-gas
> bypass to keep the head pressure up.
>
> Other chillers that I have overhauled require a very narrow band of
> condenser water temperature, such as 75-78 degrees supply temperature.  So
> modeling a wide condenser water range does not make much sense to me since
> it is not a real world application.  The chillers I have worked on either
> have a tower bypass loop or a hot gas bypass to keep the condensing pressure
> up where it belongs.  Energy is wasted when too cold a condenser water
> temperature is specified.
>
> Other manufacturers say the colder the better.
>
> Specifying variable primary chilled water flow and variable condenser water
> flow has a large impact on chiller efficiency.  I ask the manufacturers to
> provide me the kW/Ton for minimum flow, standard flow and maximum flow for
> the evaporator and condenser bundles.  A chiller that has an kW/Ton of .56
> at AHRI conditions can often have a 1.3 kW/Ton at minimum condenser flow (3
> gpm/ton) at 30% load.
>
> The IPLV is really a useless rating for a real world application since it
> assumes a certain percentage load a certain percentage of the time.  It all
> depends on the design of the system and the load profile.  It is a good
> rating to compare various chillers if they conform to the load profile.  I
> see more chillers that run in the 40-60% range 90% of the time than I see
> chillers that match the IPLV conditions.
>
> During my investment-grade reviews with our local utility, the lift of the
> chiller is always an important consideration.
>
> There was an e-mail for someone, I believe York, that offered to model any
> manufacturers chiller on this forum a few months ago.  I have had good luck
> getting the rep to provide the information that I requested as long as I
> find the right person.
>
> Paul
>
>
> ------------------------------
>
> *From:* Nick Caton <ncaton at smithboucher.com>
> *To:* Paul Diglio <paul.diglio at sbcglobal.net>;
> equest-users at lists.onebuilding.org
> *Sent:* Fri, February 25, 2011 2:50:44 PM
> *Subject:* RE: [Equest-users] using IPLV in eQuest
>
> Paul, I may not have been crystal-clear, but if someone is merely making a
> comparative analysis between two screw chillers, aren’t the relative effects
> of varying lift between the two chillers negligible?  My general
> understanding is that lift is a more critical variable when comparing VSD
> centrifugal chillers…  This is why I suggested a simpler EIR-fPLR curve
> would be sufficient in lieu of an EIR-fPLR&dT – I was trying to simplify
> Rohini’s comparative analysis.
>
>
>
> I’d agree that an EIR-fPLR&dT curve would be more precise and more
> appropriate if the goal is to better match the chiller behavior (and
> creating custom CAP-FT and EIR-FT would be even better), but I was thinking
> this would require an unnecessary amount of extra work for Rohini’s
> comparative purpose.
>
>
>
> My “suggested information to request” below for constructing EIR-fPLR&dT
> curves is based on my past experience with limitations of my local manf.
> rep’s software – they need to set certain items constant to get the numbers
> to crunch…  Have you had luck collecting PLR runs where the evaporator
> and/or condenser temp was allowed to float?  I’ve picked up through the
> lists that a better way to skin the cat may be to approach the chiller
> controls reps where they may exist, as they may have more flexible software…
>
>
>
> I throw this disclaimer out sometimes:  I certainly haven’t been doing this
> for decades!  If I’m misunderstanding something, I very much welcome
> corrections ;).
>
>
>
> Thanks,
>
>
>
> ~Nick
>
>
>
> *Error! Filename not specified.*
>
> * *
>
> *NICK CATON, E.I.T.*
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> olathe ks 66061
>
> direct 913 344.0036
>
> fax 913 345.0617
>
> www.smithboucher.com* *
>
>
>
> *From:* Paul Diglio [mailto:paul.diglio at sbcglobal.net]
> *Sent:* Friday, February 25, 2011 12:44 PM
> *To:* Nick Caton; James Waechter; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] using IPLV in eQuest
>
>
>
> Actually what everyone is calling dt is more accurately referred to as
> lift.  It is the difference between the saturated evaporating temperature
> and the saturated condensing temperature, which is different than the
> condenser water temperature and the evaporator water temperature.
>
> A more accurate curve can be built if you have the chiller manufacturer
> model both these variables for you, rather than leaving the evaporator water
> temperature constant and just varying the condenser water temperature.  Any
> change in the evaporator pressure will effect the condensing pressure and
> any change in the condensing pressure will effect the evaporator pressure.
>
> Paul
> ------------------------------
>
> *From:* Nick Caton <ncaton at smithboucher.com>
> *To:* James Waechter <jamesw at McKinstry.com>;
> equest-users at lists.onebuilding.org
> *Sent:* Fri, February 25, 2011 1:21:42 PM
> *Subject:* Re: [Equest-users] using IPLV in eQuest
>
> James et al,
>
>
>
> Rohini will need to create performance curves to make this particular
> comparison.  Otherwise using the default curves will result in identical
> part load performances.
>
>
>
> The following is excerpted from the following (short) recommended reading
> concerning what IPLV means:
> http://ashrae-cfl.org/2010/03/understanding-iplvnplv/
>
> IPLV (or NPLV) = 0.01A+0.42B+0.45C+0.12D
>
> Where:
>
> A = COP or EER @ 100% Load
>
> B = COP or EER @ 75% Load
>
> C = COP or EER @ 50% Load
>
> D = COP or EER @ 25% Load
>
> John is saying knowing only the IPLV and the 100% load condition efficiency
> (variable ‘A,’ above) is not enough information to extrapolate the IPLV
> curves to compare the two chillers.
>
>
>
> For the exercise of comparing the two non-centrifugal chillers of the same
> technology/type, I would just focus on making a custom EIR-FPLR (not
> EIR-fPLR&dT) for each chiller, and use the library CAP-FT AND EIR-FT curves.
>  My understanding is the effects of temperature on capacity and EIR outside
> of centrifugal VSD chillers is negligible.  NOTE:  Whenever using any of the
> default library chiller performance curves, that means you MUST normalize to
> and specify the chiller at ARI conditions – those curves aren’t normalized
> to anything else.
>
>
>
> So!  If you can find the IPLV A, B, C and D values for both chillers’
> curves, you could come up with your EIR-FPLR curve coefficients (*curve
> type = quadratic or cubic*) using a curve-fit in excel… or alternatively
> make eQuest figure the coefficients by entering those points as raw data.
>
>
>
> You may more easily just make your own curves, following John’s advice and
> getting part load unloading curves (100%, 90%, 80%... etc) held at a
> constant chilled & condenser temperature to match the ARI* conditions (85CWT
> if this is water cooled) at which you’re specifying the chiller
> capacity/EIR.  Again, you could either go into excel, normalize the data
> (review DOE2 help entry for EIR-FPLR), make a scatter chart, and get the
> coefficients using a curve fit… or enter the data as raw points into eQuest
> and the coefficients will be figured by eQuest… whatever makes more sense to
> you.
>
>
>
> For others and personal future reference…. If you are looking to make an *
> EIR-fPLR&dT* curve (for centrifugal chillers or otherwise):  Ask your rep
> instead for multiple (minimum 3) part load unloading runs, holding the
> delivered chilled water temp constant, and vary the condenser water
> temperature incrementally for each run (i.e. 85, 75, 65).  Choose a range of
> CWT’s that cover the anticipated range to be encountered in the actual
> design. This will get you enough data to have the minimum 3 delta-T’s
> represented in your part load data points to build this curve correctly.
> You’ll be using eQuest “raw-data” entry method to make it generate the
> coefficients.
>
>
>
> ~Nick
>
>
>
> * Rather than ARI conditions (85F CWT), you could be normalizing to Design
> condition EIR/CAP, provided you’re making a full set of custom curves in the
> same fashion.
>
>
>
> *Error! Filename not specified.*
>
> * *
>
> *NICK CATON, E.I.T.*
>
> PROJECT ENGINEER
>
> Smith & Boucher Engineers
>
> 25501 west valley parkway
>
> 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 *James Waechter
> *Sent:* Friday, February 25, 2011 10:55 AM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] using IPLV in eQuest
>
>
>
> John,
>
>
>
> If the only parameter Rohini enters into the program is the full-load EIR –
> which he said is the same for both chillers – how will eQuest know to bend
> the curves differently for the two chiller options.  It is my understanding
> that program would use the same chiller efficiency curves for both machines
> even though their IPLVs are different.
>
>
>
> In order to overcome this issue, are you saying Rohini should get chiller
> performance data from each of the manufacturers and enter his own custom
> curves?  I recall there was a discussion on that topic a few months back.
>
>
>
> Regards,
>
> James Waechter Jr., P.E., CEM, LEED A.P.
> Energy Engineer – Rocky Mountain Region
> p 303 215 4062 | m 727 686 3248
>
> *McKinstry*
> Consulting | Construction | Energy | Facility Services
>
> www.mckinstry.com
>
>
>
>
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *John Aulbach
> *Sent:* Friday, February 25, 2011 9:41 AM
> *To:* R B; eQUEST Users List
> *Subject:* Re: [Equest-users] using IPLV in eQuest
>
>
>
> Rohini:
>
>
>
> Won't happen. IPLV is a number which has one equation and 4 unknowns.
> Actually, three unknowns as you know the 100% point. You need a
> manufacturer's curve run at 85F constant condenser water temperature. Let
> eQuest do the curve bending after that. ARI curve won't work right.
>
>
>
>
>
> John R. Aulbach, PE, CEM
>
> Senior Energy Engineer
> ------------------------------
>
> *Partner Energy*
>
> 1990 E. Grand Avenue, El Segundo, CA 90245
> W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745
>
> www.ptrenergy.com | jaulbach at ptrenergy.com
>
>
> ------------------------------
>
> *From:* R B <slv3sat at gmail.com>
> *To:* eQUEST Users List <equest-users at lists.onebuilding.org>
> *Sent:* Fri, February 25, 2011 7:25:18 AM
> *Subject:* [Equest-users] using IPLV in eQuest
>
> Hi All,
>
> I would like to compare two screw chillers with same full load kW/ton and
> different IPLV kW/ton. I am using the full load number for the EIR. Where
> can the IPLV number be used? Is there some way to scale the performance
> curves to reflect different IPLV's?
>
> -Rohini
>
>
>
>
> This email is the property of McKinstry or one of its affiliates and may
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>
>
>
>
>
>
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>
> --
> Carol Gardner PE
>
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