[Equest-users] IPLV Curve Fit
Carol Gardner
cmg750 at gmail.com
Wed Jun 15 21:43:53 PDT 2011
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*
>
>
>
>
>
>
> _______________________________________________
> Equest-users mailing list
> 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
> contain confidential and/or privileged information. If you are not the
> intended recipient or have received this e-mail in error please notify the
> sender immediately and delete this e-mail. Any unauthorized copying,
> disclosure or distribution of the material in this e-mail is strictly
> forbidden.
>
>
>
>
>
> _______________________________________________
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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
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>
>
--
Carol Gardner PE
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