[Equest-users] Water-Side Economizers

[Sethi, Amarpreet]

Jeff,
 
Note however that the waterside economizer chiller will be used only as a 'all or nothing' where it is used only when it can meet all of the load, not partial loads hence possibly under estimating the energy savings.  Also it is important to have only one cooling tower assigned when using  water side economizer chiller. 
 
I have pasted the help section below that describes this - 
 
Chiller Water-Economizer

     The program assumes a water-side economizer is used in an "all or nothing" mode. If the water-side economizer can handle the entire cooling load, then it will be used. Otherwise, the loop will use its other chillers. A water-side economizer cannot precool the return flow prior to entering the chillers.

The "all or nothing" mode precludes the use of an EQUIP-CTRL sequence to coordinate the operation of an economizer chiller with other chillers. If you list a water-side economizer chiller in an EQUIP-CTRL sequence, it will be ignored.

     There must be a one-to-one correspondence between a CHW loop, a water-side economizer, and a CW loop. A CHW loop may be supplied by only one water-side economizer, and a CW loop may supply only one water-side economizer. In other words, a plant may have any number of chilled water loops having water-side economizers, but those economizers cannot draw from the same CW loop. The program will generate an error if this condition is not met.

     If a CW loop supplies a water-side economizer, it may also supply chillers serving the same CHW loop as the economizer. However, it cannot supply chillers serving other CHW loops. The program will generate an error if this condition is not met.

     A CW loop supplying a water-side economizer should have only one cooling tower. More than one cooling tower is allowed, however only the first tower defined will be checked to see if sufficient free cooling capacity is available. Once free cooling is allocated to a CW loop, the program may use any combination of towers to satisfy it. The program may underpredict the water-side economizer savings if more than one cooling tower serves a given CW loop. To minimize the underprediction, define the largest tower first.

     If there is any water-cooled packaged equipment in the SYSTEM command, this equipment will be ignored when determining whether the tower has sufficient free cooling capacity. This may cause the program to overpredict water-side economizer savings.

     For maximum effectiveness, the CHW loop should have COOL-SETPT-CTRL = LOAD-RESET. This allows the CHW temperature setpoint to rise during periods of low loads, maximizing the effectiveness of the water-cooled economizer. <blocked::javascript:RT_6037.HHClick()> 

Amarpreet Sethi, M.Sc., LEED® AP
Sustainable Building Analyst
Stantec
1932 First Avenue Suite 307
Seattle WA 98101
amarpreet.sethi at stantec.com <blocked::mailto:amarpreet.sethi at stantec.com> 
Stantec


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From: James Hansen [mailto:JHANSEN at ghtltd.com] 
Sent: Thursday, April 15, 2010 2:48 PM
To: Pasha Korber-Gonzalez; Jeff Ross-Bain
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Water-Side Economizers



Just set up a new chiller in your primary chilled water loop, and set it to type "waterside economizer".  Then create the associated pumps / power consumption, and eQuest will automatically use this chiller (in lieu of any powered chillers) whenever there is a possibility for waterside economizer based on ambient conditions and required temperature of chilled water loop to meet loads.

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez
Sent: Thursday, April 15, 2010 4:46 PM
To: Jeff Ross-Bain
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Water-Side Economizers

 

Jeff,

 

if you have chilled water coils through your unit MZ unit and the chilled water is coming from a chiller, then the water size economizing function comes from the cooling tower that is connected to the chiller which supplies the chilled water coils.  If you are talking about economizer --in general terms, then maybe you are trying to air-economize which should be able to be input in the air-side tab-cooling  for your MZ AHU.

 

Look at the plant & cooling tower for your water econo inputs.

 

Pasha

On Thu, Apr 15, 2010 at 1:40 PM, Jeff Ross-Bain <jross-bain at rbgreenbuilding.com> wrote:

Hi All,

 

I have an existing building with a multi-zone air handling system with chilled water and hot water coils. The system consists of the air handling units, a centrifugal chiller, cooling tower, and gas fired boiler. I am trying to introduce a water-side economizer into the system. In the detailed mode, I notice that a water-side economizer is not allowed with a multi-zone system. The spreadsheet input simply has an inaccessible "n/a" shown for the economizer and does not allow access.

 

Am I missing something?

 

Thanks for your help.

 

Jeffrey G Ross-Bain, PE, LEED, BEMP

Ross-Bain Green Building, LLC

404-228-2893

 

P Build Green...Save Time

 

 


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