Trane CGAX/CXAX Manual page 9

Minimum water volume for a process application
If a chiller is attached to an on/off load such as a
process load, it may be diffi cult for the controller to
respond quickly enough to the very rapid change in
return solution temperature if the system has only the
minimum water volume recommended. Such systems
may cause chiller low temperature safety trips or in the
extreme case evaporator freezing. In this case, it may
be necessary to add or increase the size of the mixing
tank in the return line or consider the optional factory-
installed buffer tank with the chiller. Some guidance on
calculating the minimum volume necessary for proper
Scroll Compressors Chillers operation are given here,
through a simplifi ed formula, which does not take in
account variations on chiller effi ciency, compressor
sequencing, evaporator inlet/outlet temperature.
Minimum recommendable volume on the hydraulic loop
V= Cc * T / (Sh * Db) where:
Cc * T = V * Db * Sh
V = Volume of the loop (l)
Cc = Cooling Capacity of the chiller biggest Stage (kW)
T = Compressor Time (min running time (s))
Db = Dead Band (K)
Sh = Brine Specifi c heat (kJ.K
Multiple Unit Operation
Whenever two or more units are used on one chilled
water loop, Trane recommends that their operation be
coordinated with a higher level system controller for
best system effi ciency and reliability. The Trane Tracer
system has advanced chilled plant control capabilities
designed to provide such operation.
CG-PRC026C-GB
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Application Considerations
9