Expert advice to show minimum efficiency compliance Table 6.8.1C [1 Attachment]

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I would appreciate your expert advice on selecting 90.1-2010 Baseline
system to show minimum efficiency compliance as given under *Table 6.8.1C*.
One of the proposed project i am working on has two* Chillers*

1. *One with Std. Dry Coolers *
2. Second chiller has special arrangement where the surrounding air of
cooling tower being cooled (dry bulb) by some sort of misting to increase
the dry cooler effectiveness during extreme outdoor condition (CZ5A) ~ 80%
lower water consumption compared to typical water cooled cooling tower. In
this hybrid cooling tower, evaporation effect is happening but not like
std. water cooled cooling tower.

? To show minimum efficiency compliance, *what condenser type do i need to
choose*; Air or Water Cooled in both the Cooling tower type; Std Dry cooler
and Hybrid Dry cooler (see image below)? ?Also find an attachment to have
more info
on the product.

?Thank you so much.


Javed Iqbal, LEED AP, CEA
Sr. Energy Analyst

javed iqbal's picture
Joined: 2012-05-18
Reputation: 0

Hi Javed,

In my opinion the air-cooled chiller efficiency should be used. As in the
hybrid cooler (with water sprayer), the water spray is limited to only 200
hours in a year which is approximately 2-5% of the total hours in a year.
So the worst case scenario would be air-cooled chiller.


Mayank Bhatnagar
Senior Project Manager

*Environmental Design Solutions Pvt. Ltd. [EDS]*
D - 1/25
Vasant Vihar
New Delhi - 110057

Mayank Bhatnagar's picture
Joined: 2011-10-02
Reputation: 0

I am inclined to agree with Mr. Bhatnagar, but think it will be worth
asking GBCI for a clarification so that you have greater confidence. The
"hybrid" nature of one air-cooled and one evaporatively cooled chiller is

James V Dirkes II, PE's picture
Joined: 2011-10-02
Reputation: 203

Are you trying to show compliance with the mandatory minimum mechanical equipment efficiency or are you trying to select the App. G or ECB baseline system and efficiency?

What fluid runs through the actual DX equipment condenser water or air? I suspect your dry coolers are still creating condenser water to cool the equipment, in which case it is water-cooled.

Cory Duggin, PE, LEED AP BD+C, BEMP
Principal/Energy Modeling Wizard
USGBC MidTN Branch Leadership Group Co-chair
TLC Engineering for Architecture


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Joined: 2013-04-16
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I think Javed?s situation is most easily explained by mapping out some of our industry?s terminology, as I can see the discussion going in many directions as we reply to each other ? If there?s one thing I?ve found consistent between great engineers, it?s probably *not* consistency of terminology (much less, between languages). With that, I?m certain some regions and individuals will disagree with parts of the following mapping, but hopefully this will help guide the majority:

* What cooling medium is piped between the chiller and condenser equipment?
* Refrigerant --> ?Air-cooled chiller? (in AHRI 550/590 & 90.1 terms)
* In the case of air-cooled chillers, the condenser is simply referred to as the condenser.
* I have not personally run into commercial/spec-grade refrigerant-circulating condensers that pre-cool the air with sprayers/misting. I?m aware they exist, but I?m not familiar with how to distinguish this feature? I guess I would call it ?evaporative cooling add-on? or ?evaporative preconditioning?
* This is a 3rd party solution a colleague of mine investigated once, but didn?t make it into the project scope:
* Water --> ?Water-cooled chiller? (in AHRI 550/590 & 90.1 terms)
* This includes water with add-mixtures, like glycol
* Is the condenser water loop closed, or exposed to air?
* Open Loop --> ?Cooling Tower?
* Closed Loop --> ?Fluid cooler?
* Terminology usage grows particularly loose here between different manufacturers and specifiers --> Best to grab a datasheet to confirm what exactly you?re dealing with
* Is water sprayed on the fluid cooler?s fins to induce evaporative cooling?
* No --> ?Dry cooler? or ?Radiator?
* Yes --> ?Evaporative Fluid Cooler? or ?Indirect Evaporative Cooler? or ?Closed Loop Cooling Tower?

With that mapping, I?m inclined to agree that Javed is dealing with a combination of ?Dry coolers? and ?Evaporative Fluid Coolers,? both of which I?d expect to be paired with water-cooled chillers. The image below leads me to feel it?s hydronic/water fluid cooling in lieu of refrigerant because:

1. The headers on the end (copper color) appear to be equally sized pipes ? if it were refrigerant I?d expect one to be narrower
2. I don?t see the condensers anywhere? it?s possible they could be remote and I?m wrong however.

I?d still advise Javed to seek out some literature / cutsheets to be certain of what the cooling medium is. I can?t be 100% certain only looking at the picture.

Hope this helps someone!


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Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at

15200 Santa Fe Trail Drive
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Lenexa, KS 66219
United States

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