# How to set the COP of a chiller as constant in eQuest?

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Dear all,
I wonder how to set the COP of a chiller as constant? after I set the chiller type, the electric input ratio type is determined, which means the self-made constant curve cannot be input.
Thanks!
Esmi

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DOE-2 modifies the COOL-EIR using several curves COOL-EIR-FT as a function of outdoor
conditions and COOL-EIR-FPLR as a function of the Part Load Ratio. I suppose you could set
those to be constant. Another way would be to just take the Cooling Load from the SS-D
report and divide that by your constant COP. But my question would be, why do you want to
do that ?

Joe Huang

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Reputation: 406

Perhaps this would come into play if you are modeling a plant with stipulated efficiencies per the USGBC DESv2.0 guidelines with the "Option 2" approach.

My post on 4/7/13 covers exactly how to create custom chiller curves for a chiller resulting in a constant EIR that matches the stipulated efficiency value of 4.4 COP + 5% losses (i.e. 0.839 kW/ton).

Thanks!

Regards,

James A. Hess, PE, CEM, BEMP

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Reputation: 601

Hi Joe,
In the simulation of a district cooling system, the guidance requires a virtual plant with a constant average efficiency.
In the DOE curves, how can I know the meaning of the equation and the coefficients in it? It seems there is no useful information in the DOE help.
Thanks!
Esmi

DOE-2 modifies the COOL-EIR using several curves COOL-EIR-FT as a function of outdoor conditions and COOL-EIR-FPLR as a function of the Part Load Ratio. I suppose you could set those to be constant. Another way would be to just take the Cooling Load from the SS-D report and divide that by your constant COP. But my question would be, why do you want to do that ?

Joe Huang

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Joined: 2011-12-13
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Hi, James,
I found you email on that day. I prefer to use the method to set the curve. Do you know how can I set Avg EIR = Max EIR = Min EIR = the EIR?
Thanks!
Esmi

Perhaps this would come into play if you are modeling a plant with stipulated efficiencies per the USGBC DESv2.0 guidelines with the ?Option 2? approach.

My post on 4/7/13 covers exactly how to create custom chiller curves for a chiller resulting in a constant EIR that matches the stipulated efficiency value of 4.4 COP + 5% losses (i.e. 0.839 kW/ton).

Thanks!

Regards,

James A. Hess, PE, CEM, BEMP

From:equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Tuesday, April 16, 2013 9:36 PM
To:equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

DOE-2 modifies the COOL-EIR using several curves COOL-EIR-FT as a function of outdoor conditions and COOL-EIR-FPLR as a function of the Part Load Ratio. I suppose you could set those to be constant. Another way would be to just take the Cooling Load from the SS-D report and divide that by your constant COP. But my question would be, why do you want to do that ?

Joe Huang

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Joined: 2011-12-13
Reputation: 0

Do you not have a copy of a DOE-2.2 or DOE-2.1E manual? That would make it hard to
understand how DOE-2 works.
DOE-2 has many performance curves, depending on the type of equipment. The EIR-FT curves
are either bi-linear or bi-quadratic functions of the entering wetbulb and outdoor drybulb
temperature. The EIR-FPLR curves can be linear, quadratic, or cubic functions of the Part

By the way,what I said yesterday was in reference to packaged SYSTEMS. If your model
contains a PLANT model with a Chiller, then
the keywords for the chiller performance curves change somewhat.

Joe Huang

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Joined: 2011-09-30
Reputation: 406

After identifying the curves in play per Joe's suggestion, you could achieve a constant COP, independent of part load or other variables, by making a set of custom curves (of appropriate/acceptable type) using coefficient inputs.

Example from the library:

CentH2O-EIR-fPLR&dT looks like this from the library before modification. This curve works alongside others to determine how to modify the input EIR for a chiller:
[cid:image001.png at 01CE3B79.01D745D0]

What we want is for this and all the other curves to return a value of 1.0, whatever the hourly variables throw at it. Simply enter all coefficients preceding a variable (b,c,d,e,f) to 0. Set the coefficient for the curve's constant (a) at 1.0:

[cid:image003.png at 01CE3B79.8275C180]

Doing the same for all associated curves (again, read up in the help/documentation for your particular equipment to be sure), at all hours the chiller in question will operate at the specified EIR without variance.

NICK CATON, P.E.

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Reputation: 805

Nick,

One point of correction regarding curves to provide constant COP... I'm
pretty sure you do not want the EIR-FPLR curve to be constant 1.0. The
value of that curve is actually (normalized EIR)*(part load ratio). So if
you want constant EIR, then the curve should just equal PLR. That's a
straight line between (0,0) and (1,1). So the "a" coefficient should be
zero and the "b" coefficient should be 1.0. All other coefficients for that
curve should be zero.

*Erik Kolderup, PE, LEED AP*

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Erik,

You're right. It should be a straight diagonal line from 0,0 to 1,1.

Joe Huang

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Joined: 2011-09-30
Reputation: 406

Absolutely, and thanks for correcting me guys!

All: Apologies for just throwing the concept out there without thinking it through totally. Here's a fresh shot at the procedure with a more complete explanation, to make amends and reinforce the lesson for myself. I'm wide open for corrections if I've missed something =):

The typical function for determining a chiller's hourly energy consumption is:
Elechour = Caphour * EIR * EIRf(t1,t2) * EIRf(PLR,dT) / 3413 Btu/Kw

Erik's direction, setting only the 'b' coefficient to 1.0 and the rest to zero, turns EIRf(PLR,dT) into a linear curve that will very simply return the PLR. This reduces the formula to:
Elechour = Caphour * EIR * EIRf(t1,t2) * PLR / 3413 Btu/kW

Following my original direction for coefficients, setting only 'a' to 1.0 and the rest to zero, will turn EIRf(t1,t2) into a curve that will always return 1.0. This reduces the formula to:
Elechour = Caphour * EIR * 1.0 * PLR / 3413 Btu/kW

By their respective definitions in this context (see DOE2 entry below), (Caphour * PLR) equals the Hourly Load, in Btuh. The formula is therefore reduced to:
Elechour = "The Hourly Load (Btuh)" * EIR * / 3413 Btu/kW

So now we are finally utilizing the input EIR every hour, as intended! Interesting to note, one need not even touch the CAPf(t1,t2) curve as its effects are canceled out along the way.

NICK CATON, P.E.

PS: ...If all this is looking foreign, here's the DOE2 help entry I'm starting from:

[cid:image004.png at 01CE3BA2.9F7FB2D0]

[cid:489575314 at 22072009-0ABB]

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Hi Joe,
Is the DOE-2.2 manual the DOE help in the eQuest?
Esmi

Do you not have a copy of a DOE-2.2 or DOE-2.1E manual? That would make it hard to understand how DOE-2 works.
DOE-2 has many performance curves, depending on the type of equipment. The EIR-FT curves are either bi-linear or bi-quadratic functions of the entering wetbulb and outdoor drybulb temperature. The EIR-FPLR curves can be linear, quadratic, or cubic functions of the Part Load Ratio (PLR).

By the way,what I said yesterday was in reference to packaged SYSTEMS. If your model contains a PLANT model with a Chiller, then
the keywords for the chiller performance curves change somewhat.

Joe Huang

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Joined: 2011-12-13
Reputation: 0

Dear Nick,
I now know how to set the COP of a chiller. But I also have two quesions:
1 where to find the meaning of these parameters of the curve? Are them in the DOE help?
2 How to verify that the COP is set as constant from the simulation output file of eQuest?
Thanks!
Esmi

Absolutely, and thanks for correcting me guys!

All: Apologies for just throwing the concept out there without thinking it through totally. Here?s a fresh shot at the procedure with a more complete explanation, to make amends and reinforce the lesson for myself. I?m wide open for corrections if I?ve missed something =):

The typical function for determining a chiller?s hourly energy consumption is:

Elechour = Caphour * EIR * EIRf(t1,t2) * EIRf(PLR,dT) / 3413 Btu/Kw

Erik?s direction, setting only the ?b? coefficient to 1.0 and the rest to zero, turns EIRf(PLR,dT) into a linear curve that will very simply return the PLR. This reduces the formula to:

Elechour = Caphour * EIR * EIRf(t1,t2) * PLR / 3413 Btu/kW

Following my original direction for coefficients, setting only ?a? to 1.0 and the rest to zero, will turn EIRf(t1,t2) into a curve that will always return 1.0. This reduces the formula to:

Elechour = Caphour * EIR * 1.0 * PLR / 3413 Btu/kW

By their respective definitions in this context (see DOE2 entry below), (Caphour * PLR) equals the Hourly Load, in Btuh. The formula is therefore reduced to:

Elechour = ?The Hourly Load (Btuh)? * EIR * / 3413 Btu/kW

So now we are finally utilizing the input EIR every hour, as intended! Interesting to note, one need not even touch the CAPf(t1,t2) curve as its effects are canceled out along the way.

NICK CATON, P.E.

PS: ?If all this is looking foreign, here?s the DOE2 help entry I?m starting from:

From:equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Wednesday, April 17, 2013 6:56 PM
To:equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

Erik,

You're right. It should be a straight diagonal line from 0,0 to 1,1.

Joe Huang

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Joined: 2011-12-13
Reputation: 0

FYI, email I sent on 4/7/13 at 10:12 PM CST shows how to verify COP is constant.

Thanks!

Regards,

James A. Hess, PE, CEM, BEMP

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Joined: 2011-09-30
Reputation: 601

I was referring to the DOE-2 Supplement, Version 2.1E, produced by LBNL in 1993
(LBL-34947). I have not looked at the help function of eQUEST, so I can't tell how
detailed is it.

Joe Huang

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Joined: 2011-09-30
Reputation: 406

Highly recommended for anyone using eQuest - the manuals behind the DOE-2 engine: http://doe2.com/DOE2/

I am constantly referring to these every time I get stuck and need to know how something in eQuest works.

Cheers,

Daniel Knapp, PhD, P Phys, LEED? AP O+M

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Thanks Dan!

Scrolling further down that page than I have before, following the links to each volume, I've found my answer:

"These documents are the basis of the eQUEST on-line help system but contain a more complete and up-to-date description of the details of the DOE-2.2 version within the current release of eQUEST."

Better keep these PDF's handy as well!

NICK CATON, P.E.

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Joined: 2011-09-30
Reputation: 805

This is something I haven't ever fully resolved for myself actually... eQuest contains a set of DOE-2.2 manual volumes, found under the eQuest "Help" menu.
[cid:image005.png at 01CE3F4B.993AAEA0]

I believe the first 4 volumes are the "core" DOE2.2 volumes, and the other volumes have been appended over time as eQuest/DOE2 have developed in more recent years. I'm not clear on whether these in sum are any more or less "complete" than past or present manuals for the underlying DOE2 simulation engine itself. I am pretty sure some parts of this are compiled by & for eQuest specifically (Volume 5: Compliance Analysis in particular jumps to mind).

More specifically to Esmireta's follow up query, you can find the entry I cited on Chiller Energy Consumption, and explore the associated inputs further, in a few ways:

First, navigate to "DOE-2 Help" from the Help context menu.
[cid:image003.png at 01CE3F47.FE73C170]

Second, while working in eQuest and particularly after the wizards, you can also right-click most input fields to pull up a context-sensitive index of sorts to lead you to appropriate entries in the DOE2 manuals - this is the primary way I access & navigate the supporting documentation in practice:
[cid:image004.png at 01CE3F4A.293FF430]

Regards,

NICK CATON, P.E.

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Joined: 2011-09-30
Reputation: 805

Another point that might help some folks who are trying to model constant chiller COPs:

I needed to use the existing district plant method for a local utility rebate recently, and by inspecting the PS-H report for my "chiller," which represented the plant, I found that I was not getting constant EIRs after creating my own curves, etc. It was also not a constant error, getting worse in the cooler months and closer to my expected value in the summer.

The fix was to remove any peripherals or vampire loads from the chiller power in the chiller properties dialog. I modeled the plant as a single, air-cooled chiller, set my calculated EIR, applied the flat curves (as noted by others below), allowed the "Min Ratio" to go down to 0.01, set "Elec to Condenser" to zero (assuming that is already calculated in my overall EIR), and set "Start-up Time" and "Standby Time" to zero, since in reality the water is available when the building needs it and we're not firing up a chiller just for me.

Seemed obvious after the fact, but drove me crazy for a little while.

Thanks,
Wesley

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Hi Nick,
Thank you so much for your patience!
Esmi

? 2013-04-23 00:40:51?"Nick Caton" ???

This is something I haven?t ever fully resolved for myself actually? eQuest contains a set of DOE-2.2 manual volumes, found under the eQuest ?Help? menu.

I believe the first 4 volumes are the ?core? DOE2.2 volumes, and the other volumes have been appended over time as eQuest/DOE2 have developed in more recent years. I?m not clear on whether these in sum are any more or less ?complete? than past or present manuals for the underlying DOE2 simulation engine itself. I am pretty sure some parts of this are compiled by & for eQuest specifically (Volume 5: Compliance Analysis in particular jumps to mind).

More specifically to Esmireta?s follow up query, you can find the entry I cited on Chiller Energy Consumption, and explore the associated inputs further, in a few ways:

First, navigate to ?DOE-2 Help? from the Help context menu.

From here, you can navigate to the previously appended chiller energy consumption entry. Here?s a better citation for those who aren?t seeing images in my emails: Volume 2 > HVAC Components > CHILLER > Chiller Energy Consumption. You can also read up on all the associated BDL inputs by highlighting the branch elements following in the tree view:

Second, while working in eQuest and particularly after the wizards, you can also right-click most input fields to pull up a context-sensitive index of sorts to lead you to appropriate entries in the DOE2 manuals ? this is the primary way I access & navigate the supporting documentation in practice:

Regards,

NICK CATON, P.E.

From:equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Monday, April 22, 2013 10:40 AM
To: Esmireta
Cc:equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

I was referring to the DOE-2 Supplement, Version 2.1E, produced by LBNL in 1993 (LBL-34947). I have not looked at the help function of eQUEST, so I can't tell how detailed is it.

Joe Huang

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Joined: 2011-12-13
Reputation: 0

Hi Wesley,
Actually, air-cooled chiller is required per ASHRAE90.1, thus, no energy consumption from cooling tower and cooling pumps will be included.
Thanks!
Esmi

Another point that might help some folks who are trying to model constant chiller COPs:

I needed to use the existing district plant method for a local utility rebate recently, and by inspecting the PS-H report for my ?chiller,? which represented the plant, I found that I was not getting constant EIRs after creating my own curves, etc. It was also not a constant error, getting worse in the cooler months and closer to my expected value in the summer.

The fix was to remove any peripherals or vampire loads from the chiller power in the chiller properties dialog. I modeled the plant as a single, air-cooled chiller, set my calculated EIR, applied the flat curves (as noted by others below), allowed the ?Min Ratio? to go down to 0.01, set ?Elec to Condenser? to zero (assuming that is already calculated in my overall EIR), and set ?Start-up Time? and ?Standby Time? to zero, since in reality the water is available when the building needs it and we?re not firing up a chiller just for me.

Seemed obvious after the fact, but drove me crazy for a little while.

Thanks,

Wesley

Celebrating 25 Years

Mechanical Engineers + Electrical Engineers + Sustainable Design

Wesley Care, EIT | Mechanical Project Engineer|* wesley.care at esdaz.com|(480.481.4973|6480.481.4903

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Hi, James,
I found that email! It really helps me out!
Thanks!
Esmi

FYI, email I sent on 4/7/13 at 10:12 PM CST shows how to verify COP is constant.

Thanks!

Regards,

James A. Hess, PE, CEM, BEMP

From:equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Esmireta
Sent: Sunday, April 21, 2013 11:55 PM
To: Nick Caton
Cc:equest-users at lists.onebuilding.org; Erik Kolderup
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

Dear Nick,

I now know how to set the COP of a chiller. But I also have two quesions:

1 where to find the meaning of these parameters of the curve? Are them in the DOE help?

2 How to verify that the COP is set as constant from the simulation output file of eQuest?

Thanks!

Esmi

Absolutely, and thanks for correcting me guys!

All: Apologies for just throwing the concept out there without thinking it through totally. Here?s a fresh shot at the procedure with a more complete explanation, to make amends and reinforce the lesson for myself. I?m wide open for corrections if I?ve missed something =):

The typical function for determining a chiller?s hourly energy consumption is:

Elechour = Caphour * EIR * EIRf(t1,t2) * EIRf(PLR,dT) / 3413 Btu/Kw

Erik?s direction, setting only the ?b? coefficient to 1.0 and the rest to zero, turns EIRf(PLR,dT) into a linear curve that will very simply return the PLR. This reduces the formula to:

Elechour = Caphour * EIR * EIRf(t1,t2) * PLR / 3413 Btu/kW

Following my original direction for coefficients, setting only ?a? to 1.0 and the rest to zero, will turn EIRf(t1,t2) into a curve that will always return 1.0. This reduces the formula to:

Elechour = Caphour * EIR * 1.0 * PLR / 3413 Btu/kW

By their respective definitions in this context (see DOE2 entry below), (Caphour * PLR) equals the Hourly Load, in Btuh. The formula is therefore reduced to:

Elechour = ?The Hourly Load (Btuh)? * EIR * / 3413 Btu/kW

So now we are finally utilizing the input EIR every hour, as intended! Interesting to note, one need not even touch the CAPf(t1,t2) curve as its effects are canceled out along the way.

NICK CATON, P.E.

PS: ?If all this is looking foreign, here?s the DOE2 help entry I?m starting from:

From:equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Joe Huang
Sent: Wednesday, April 17, 2013 6:56 PM
To:equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] How to set the COP of a chiller as constant in eQuest?

Erik,

You're right. It should be a straight diagonal line from 0,0 to 1,1.

Joe Huang

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Joined: 2011-12-13
Reputation: 0

Since I've had several requests this week for the old DOE-2.1E documentation, I've decided
to put them on my Web site for public access. The PDFs are quite large because all the
documentation were scanned from paper copies.

Joe Huang

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Joined: 2011-09-30
Reputation: 406

Thank you Joe. That's very helpful!

Daniel Knapp, PhD, P Phys, LEED? AP O+M

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Joined: 2011-09-30
Reputation: 0

http://bepan.info/doe21e-program
Varkie
http://www.iit.edu/arch/faculty/thomas_varkie.shtml

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Varkie
Do you still need the password to unzip the DOE2.1e zip files? I
recall that at one time you had to fill out the license agreement,