[Equest-users] Waterside Economizer

[Sethi, Amarpreet]

Hi Charles,

 

You can model this using a chiller of the type called 'water economizer chiller' this has some limitations however.  

 

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.

 

Enjoy!

Amarpreet

 

 

Amarpreet Sethi MSc LEED AP
Sustainable Building Analyst
Stantec
amarpreet.sethi at stantec.com 

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

 

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From: Charles Land [mailto:cland at geo-marine.com] 
Sent: Wednesday, June 02, 2010 8:26 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Waterside Economizer

 

Does anyone know a way to do waterside economization other than through the airside tabs.  The building I'm currently modeling has older multizone systems with a water to water heat exchanger for waterside economization.  Equest does not give the option for waterside economization for multizone units.  I thought there may be a way to create a heat exchanger and accomplish this through a water side route but have so far been unsuccessful.

 

 

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