[Equest-users] IPLV Curve Fit
Paul Diglio
paul.diglio at sbcglobal.net
Fri Jun 17 06:30:14 PDT 2011
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
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), 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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---------- 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
________________________________
PartnerEnergy
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
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Carol Gardner PE
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