[Equest-users] IPLV Curve Fit

[Robby Oylear]

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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