[Equest-users] LEED baseline chiller COP shoulbe determined by building peak load or single chiller capacity

Fri Nov 20 04:28:30 PST 2020

Hi Yongqing,

Based on the information that I’ve seen, you are right. The total building load is used to determine type and quantity of chillers, but the efficiency (COP or kW/ton) is based on the size of each chiller not the total building load. I would suggest requesting a call with reviewer to discuss (this is allowed). Sometimes they bring in other people who didn’t do the review when you challenge them on something like this. My guess is that the specific reviewer that provided this comment is mistaken and interpreted this wrong, but that if the GBCI Energy heads got involved that they would agree with you.

Good luck.

Alex Chapin EIT, BEMP, LEED AP BD+C, O+M
Energy Engineer | Mason & Hanger
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From: Yongqing [mailto:zhaoyongqing1987 at 126.com]
Sent: Tuesday, November 17, 2020 11:25 PM
To: equest-users <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] LEED baseline chiller COP shoulbe determined by building peak load or single chiller capacity

Hi Fiona,

I kown that you mentioned.

The total capacity of my base building is 444 tons(data from  energy model result for LEED CS).And in my enegy mode for LEED cs ,two water-cooled chillers with 222 tons were modeled.And the cooling efficiency for the both chillers is 0.634 kW/ton.

And why in CI project,I should model the chiller efficiency as 0.576kW/ton?

The credit indicates that the Baseline Case water side equipment (i.e. chillers, pumps, etc.) type, size and related controls such as COP, secondary pump control, etc., must be determined based on the whole-building (Base building) capacity,but not based on the Base building peak load!

My understanding is shown as following：

For example, if my base building peak load is 400 tons,and my project peak load is 200 tons.We shoulde use the 400 tons to determined the number of chillers ,that is 2 chillers.And then the capacity for each chiller is 200 tons.Finally according to Table 6.8.1C, the cooling efficiency of each chiller should be 0.637.

At 2020-11-18 11:07:30, "Xiang, Yun (Fiona)" <Fiona.Xiang at atkinsglobal.com<mailto:Fiona.Xiang at atkinsglobal.com>> wrote:
Hi Yongqing,

If your project is CI project, the reviewer is right.
For CI project, the Baseline Case water side equipment (i.e. chillers, pumps, etc.) type, size and related controls such as COP, secondary pump control, etc., must be determined based on the whole-building (Base building) capacity, not only your project.
For example, If the base building has total cooling capacity of 1000 tons, and your project only has cooling capacity of 100 tons. Then the Baseline case should be modeled as two water-cooled centrifugal chillers with 0.576 kW/ton (500tons).

Fiona Xiang LEED AP BD+C  WELL AP
Senior Project Engineer
Asia Pacific
Energy & Sustainability / Engineering, Design & Project Management

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From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of Yongqing via Equest-users
Sent: Wednesday, November 18, 2020 10:49
To: equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] LEED baseline chiller COP shoulbe determined by building peak load or single chiller capacity

Hi,everyone

Recently, I was working on a LEED project,And the reviewer gave below comments:

The MEPC Water-Side HVAC tab indicates that the Baseline Case has been modeled with the two-water cooled centrifugal chillers with each chiller cooling efficiency - kW per ton of 0.634 (full load), which appears to be inappropriate. Note that the Baseline Case water side equipment (i.e. chillers, pumps, etc.) type, size and related controls such as COP, secondary pump control, etc., must be determined based on the whole-building capacity. Based on the base building information provided, it is likely that the Baseline Case should be modeled with two water-cooled centrifugal chillers per ASHRAE 90.1-2010 Table G3.1.3.7<https://urldefense.com/v3/__http:/3.1.3.7__;!!OepYZ6Q!sfr3WuMPL4_O2ncZ60QOq9V2x-x4GqZUWFyin9fICi_fyB99XjcgcktttHWe-RBPvLs$> with each chiller cooling efficiency kW per ton of 0.576 (full load) and 0.549 (part load; if following path A).

Update the Baseline Case energy model and ensure that the Baseline Case chiller type and associated controls are modeled following the requirements of ASHRAE 90.1-2010 Appendix G (based on the base building peak load).

He(She) said LEED baseline chiller cop shoulde be based on building peak load,rather than single chiller capacity.For example,two chillers were modeled in my baseline case,and the capacity for each chiller is 160tons,and I use the capacity of 160tons to determine the COP, kW per ton of 0.634.And according to comments, I should determined the COP based on 320 tons,that is kW per ton of 0.576.

Which is right?

Thank you!

Yongqing

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