[Equest-users] Air-cooled Chiller EIRFPLR curve in eQUEST

[Bishop, Bill]

Kusum,

The entry for “Chiller Energy Consumption” in the DOE-2 help files is a good place to start. It explains how hourly chiller energy is determined.
The three curves that determine hourly chiller energy are EIR-FT, EIR-FPLR and CAPACITY-FT. I believe the data in your attachment could help you create a custom curve for any one of these inputs, given the other two. I would create a custom EIR-FT curve based on the default eQUEST curves for EIR-FPLR and CAPACITY-FT for an air-cooled chiller, but you could create a custom EIR-FPLR curve using default curves for the other two as well.

The independent variables (knowns) that you have based on your manufacturer’s data are CHW-T, DBT, (or t1, t2 per the help menu description), Load, rated Capacity and EIR. (More correctly, you have design capacity at 105F since the eQUEST rated capacity is based on 95F outdoor drybulb.)
The dependent variables are hourly capacity as a function of temperature Caphour, and PLR which is a function of load and Caphour.
The manufacturer’s data column for “Capacity” is mislabeled. It is actually load, as seen by multiplying the “Percent Loading” column by the design capacity. Actual chiller capacity should increase slightly with decreasing ambient temperature. So the table doesn’t actually show you the part load ratio PLR, which is the load divided by the hourly capacity.

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Monday, October 19, 2015 12:26 PM
To: Kusum Sekhalia <skusum3 at gmail.com>; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Air-cooled Chiller EIRFPLR curve in eQUEST

Hi Kusem:

I don't have too much time, but if you are holding a 44 DegF CHW temp and varying the outdoor temp (essentially your condenser), aren't you simply changing the capacity of the chiller based on outdoor temp. I believe you need to leaving the outdoor temp at a fixed temp, then apply your part load  and the equivalent kW.

eQuest will vary the chiller peak based on outdoor loadwith onwe of the other chiller curves (guys, help me).

John Aulbach


On Monday, October 19, 2015 9:05 AM, Kusum Sekhalia <skusum3 at gmail.com<mailto:skusum3 at gmail.com>> wrote:

Hi all,

I am trying to create an air-cooled chiller EIRFPLR curve but am getting errors. I am not able to figure out what am I doing wrong? I have attached the part load data from the manufacturer. Can someone help me or provide me some information which shows step by step on how to create the curve. I am using the Design guidelines HVAC simulation pdf to create the curve but not successful so far. Please help.

Thank you in advance.

Kusum Shekhlia

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