I have been using eQuest to evaluate chiller performance for retrofit
projects. I have not had a problem modeling air-cooled, but I can't seem to
get the data from the reps that I would like for water-cooled centrifugal
projects. I have settled on using standard curves for CAPFT and EIRFT and
using a cubic curve with coefficients created through a curve fit in excel
for EIRFPLR.
The manufacturers reps aren't able to produce a capacity or EIR curve as a
function of temperature (entering condenser water temp). Has this been
everyone's experience with this.
I'm attaching the excel file I created to calculate all of this.
Any feedback is appreciated. I'm just concerned about the data I'm
reporting to the client without touching those curves.
Thanks,
Jordan Jackson.
Michael,
Thanks for the spreadsheet. That is definitely more elaborate than the one
I put together.
I was able to successfully model air-cooled screws using the spreadsheet I
attached, but the issue I'm running into with the water-cooled centrifugals
is that the capacity provided by the rep does not change as a result of
entering condenser water temperature. KW changes, but tonnage does not.
This creates an unrealistic curve for CAPFT and EIRFT.
I'm at the mercy of the reps to provide this data and so far I have struck
out. I was just curious if there was something I'm missing. Does something
need to be held constant that will allow the capacity to change based on
entering condenser water temperature and leaving chilled water temperature?
On a similarly frustrating note... I'm trying to come up with a workaround
to model series chillers in eQuest with free cooling on the upstream
chiller. From reading the DOE manual it seems waterside economizer won't do
what I need it to since I can't be in WSE and supplementing with the
downstream chiller. I considered combining performance of the two chillers
into one machine, but I haven't totally figured out how that will work.
Any ideas are welcome.
Thanks,
Jordan Jackson.
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Jordan:
You can use the equipment management to allow one virtual chiller that is the WSE to run up to a certain capacity, then stage on a single chiller, and then a virtual chiller that is equivalent to the performance of the two SCF chillers as a unit.
The chiller vendor most likely will need to provide the performance data of the two SCF chillers working together as a unit. I?m not sure you have the data necessary to construct that performance curve yourself from the standard submittals.
So to be clear, you?ll have three chillers in your model:
1. Equivalent WSE chiller
2. A single chiller, as designed
3. A virtual chiller for both machines operating in series counterflow
You won?t have two single chillers as designed, eQUEST would operate these in parallel instead of in series.
David
David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates
Jordan:
With respect to WSE, my practice to handle simultaneous chiller/WSE
operations is to ?roll my own? waterside economizer
?chiller/heat-exchanger? leveraging load management inputs. I?ve attached
a discussion wherein I provided an outline for a starting point, and have
also copied that text below this response since my attachments haven?t been
working of late.
In short, you should be able to have your WSE operation function
independently of the other chillers on the same loop. It will be up to you
to build on this framework to be sure to account for the pumping/fan
energies/additional head associated with that ?free cooling? operation (as
applicable).
~Nick
*NICK CATON, P.E.*
*Owner*
*Caton Energy Consulting*
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office: 785.410.3317
www.catonenergy.com
Hi Nikola, good to hear from you!
An approach I like to start with (sometimes this is a rough approximation,
other times it is very accurate & appropriate), is:
1. Establish an outside temperature at and below which the waterside
economizer is designed to handle the building?s cooling loads (or largely
so)
2. Create a ?free cooling? chiller with an EIR a hair above zero
(something like 0.0000001), attach it to the CHW loop(s) servicing your
coils, alongside the regular chiller(s)
3. Create a pair of equipment control sequences: ?Free? and ?Normal?
a. For the ?Free? control sequence, assign the ?free cooling chiller?
in the first row to handle loads first. You may optionally also assign the
actual chillers and associated capacity ranges for each.
b. For the ?Normal? control sequence, specify your normal chiller
sequence of operations
4. Then create a Load Management of type OA-TEMP.
a. Set the outside air temperature below which free cooling is active
under management sequence 1, and assign the free cooling control sequence
defined in the previous step.
b. Set management sequence 2 to a maximum OSA temp of 999, and assign
the normal control sequence from the previous step
Integrating WSE into eQuest is one of those things I always plan on
spending extra time on ? the devil is in the details! I don?t believe
waterside economizer systems are something you can make a simple rote
procedure around, as actual waterside economizer system
operations/limitations are varied and nuanced. Consider this a simple
outline to convey the approach concept & get you started. I would
particularly advise paying close attention to your pumping and heat
rejection energies from this point forward.
Hope that helps get you started - Happy new year!
~Nick
*NICK CATON, P.E.*
*Owner*
*Caton Energy Consulting*
1150 N. 192nd St., #4-202
Shoreline, WA 98133
office: 785.410.3317
www.catonenergy.com
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
] *On Behalf Of *Nikola Kravik
*Sent:* Tuesday, December 30, 2014 8:45 AM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] Water side economizer
Hi eQuest users,
Can you please share your experiences with implementing WSE successfully
and workarounds in v3.65?
Thank you,
Nikola
Nikola Kravik, BEMP, LEED AP
Energy Engineer
ASHRAE Golden Gate BOG
IBPSA USA San Francisco Committee
*Willdan Energy Solutions*
*Celebrating 50 years of service*
6120 Stoneridge Mall Road, Suite 250
Pleasanton, CA 94588
T. 925.416.4200 ext. 1228
D. 925.416.4228
C. 925.719.5883
F. 925.737.0174
Email: nkravik at willdan.com
www.willdan.com
*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Brian Fountain
*Sent:* Wednesday, April 08, 2015 4:12 PM
*To:* jordan jackson; Michael Busman; equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Centrifugal Chiller Curves
DOE-2.3 (eQUEST 3.70) does serial chillers. DOE-2.2 does not and as you
observed the WSE will only work when it can take all the load. Have not
tried. The DOE-2.3 WSE in series.
*From: *jordan jackson
*Sent: *Wednesday, April 8, 2015 6:31 PM
*To: *Michael Busman; equest-users at lists.onebuilding.org
*Subject: *Re: [Equest-users] Centrifugal Chiller Curves
Michael,
Thanks for the spreadsheet. That is definitely more elaborate than the one
I put together.
I was able to successfully model air-cooled screws using the spreadsheet I
attached, but the issue I'm running into with the water-cooled centrifugals
is that the capacity provided by the rep does not change as a result of
entering condenser water temperature. KW changes, but tonnage does not.
This creates an unrealistic curve for CAPFT and EIRFT.
I'm at the mercy of the reps to provide this data and so far I have struck
out. I was just curious if there was something I'm missing. Does something
need to be held constant that will allow the capacity to change based on
entering condenser water temperature and leaving chilled water temperature?
On a similarly frustrating note... I'm trying to come up with a workaround
to model series chillers in eQuest with free cooling on the upstream
chiller. From reading the DOE manual it seems waterside economizer won't do
what I need it to since I can't be in WSE and supplementing with the
downstream chiller. I considered combining performance of the two chillers
into one machine, but I haven't totally figured out how that will work.
Any ideas are welcome.
Thanks,
Jordan Jackson.
David/Nick,
The virtual chiller idea makes a lot of sense. I will play around with it tomorrow. I remember reading the post that you attached after re-reading. Too bad my sleep deprived brain couldn't get there first.
Thanks,
-Jordan.
Sent from my iPhone
Jordan,
In order to map the compressor properly for CAPFT you need to have the min. of 10 full load data points (tons, kW) at different leaving chilled and entering condenser water temps I discussed previously.
The chiller mfg. sales engineers have the software to run this for you. They probably don?t want to if they think there?s nothing in it for them. Tell them you have a project to install new chillers and the ability to properly model them will dictate whether you select Trane, Carrier, York, McQuay, etc. for the project. You might also tell them that the level of cooperation and assistance will influence the selection decision.
If your project is an energy savings performance contract where savings are guaranteed and there will be M&V of the chiller (certified mfg. test report or field tested), you might want to degrade the fouling factors a bit to add some conservatism to your model.
My best,
Mike
Mike Busman, C.E.M.
Lead Project Engineer
765 The City Dr South Suite 475
Orange, CA 92868
T. 657-216-3261
M. 310.387.2083
mbusman at opterraenergy.com
[OpTerra]
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