Lista

Applications
Engineering
Manual
Multiple-Chiller-System
Design and Control
SYS-APM001-EN (March 2001)

Multiple-Chiller-System
Design and Control
Mick Schwedler, applications engineer
Ann Yates, information designer
Preface
The Trane Company, in proposing these system design and application
concepts, assumes no responsibility for the performance or desirability of any
resultingsystem design. System design is the prerogative and responsibility of
the system designer.
© 2001 American SYS-APM001-EN Standard Inc. All rights reserved
This manual examines chilled-water-system components, configurations,
options, and control strategies. The goal is to provide system designers with
options they can use to satisfy the building owners’ desires, but this manual is
not intendedto be a complete chiller-system design manual.
System designers may get the most use from this manual by familiarizing
themselves with chilled-water-system basics and understanding the benefits of
various options. Thereafter, when a specific job will benefit from these
advantages, consult appropriate sections of the manual in detail.
The Engineers Newsletters that are referenced in this manualare available at:
www.trane.com/commercial/library/newsletters.asp
SYS-APM001-EN iii
Contents
Introduction ...........................................................................................1
Chilled-Water-Plant Basics ...............................................................2Chiller...........................................................................................................2
Loads ...........................................................................................................5
Chilled-water distribution system ............................................................7
Condenser-water system .........................................................................10
Controls....................................................................................................11
Chilled-Water-System Options ....................................................13
Chilled- and condenser-water temperatures .........................................13
Chilled- and condenser-water flow rates ...............................................15
Misconceptions about low-flow rates .....................................................24System Configurations ...................................................................27
Parallel chillers .........................................................................................27
Series chillers ...........................................................................................29
Primary–secondary (decoupled) systems ..............................................31Pumping Arrangements...................................................................36
Flow-based control ...................................................................................38
Chiller sequencing ...................................................................................39
Variable-Primary-Flow Systems ..................................................40
VPFadvantages ........................................................................................41
VPF caveats ..............................................................................................41
Chiller sequencing ...................................................................................43
Chilled-Water-Control Options ................................................... 47Chilled-water reset—raising and lowering.............................................47
Critical valve reset ....................................................................................48
Design Considerations ....................................................................49
Chilled-water pump configurations.........................................................49
Bypass line...