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Operating Principles
General Requirements
Operation and maintenance information are covered in this
section. This includes both 50 and 60 Hz centrifugal chillers
®
equipped with the Tracer
control system. This information pertains to all chiller types
unless differences exist, in which case the sections are
listed by chiller type as applicable and described
separately. By carefully reviewing this information and
following the instructions given, the owner or operator can
successfully operate and maintain the chiller. If mechanical
problems do occur, however, contact a Trane service
technician to ensure proper diagnosis and repair of the
unit.
Important: Although CenTraVac™ chillers can operate
through surge, it is NOT recommended to
operate them through repeated surges over
long durations. If repeated surges of long
durations occur, contact your Trane Service
Agency to resolve the issue.
Cooling Cycle
Duplex™ CenTraVac™ chillers have two refrigerant circuits
that operate as their own independent circuits. These
circuits are discussed as individual chiller refrigeration units
in the following section. The sequence of operation of the
two refrigeration circuits is discussed in a later section.
When in the cooling mode, liquid refrigerant is distributed
along the length of the evaporator and sprayed through
small holes in a distributor (i.e., running the entire length of
the shell) to uniformly coat each evaporator tube. Here, the
liquid refrigerant absorbs enough heat from the system
water circulating through the evaporator tubes to vaporize.
The gaseous refrigerant is then drawn through the
eliminators (which remove droplets of liquid refrigerant from
the gas) and the first-stage variable inlet guide vanes, and
into the first-stage impeller.
CDHH 3-Stage Compressor 1 or 2
Compressed gas from the first-stage impeller flows through
the fixed, second-stage inlet vanes and into the second-
stage impeller. Here, the refrigerant gas is again
compressed, and then discharged through the third-stage
variable guide vanes and into the third-stage impeller. After
the gas is compressed a third time, it is discharged into the
condenser. Baffles within the condenser shell distribute the
compressed refrigerant gas evenly across the condenser
tube bundle. Cooling tower water circulated through the
condenser tubes absorbs heat from the refrigerant, causing
it to condense. The liquid refrigerant then passes through
an orifice plate and into the economizer.
The economizer reduces the energy requirements of the
refrigerant cycle by eliminating the need to pass all
gaseous refrigerant through three stages of compression
(refer to the following figure). Notice that some of the liquid
76
AdaptiView™ Symbio™ 800
refrigerant flashes to a gas because of the pressure drop
created by the orifice plates, thus further cooling the liquid
refrigerant. This flash gas is then drawn directly from the
first and second stages of the economizer into the third-
and second-stage impellers of the compressor,
respectively. All remaining liquid refrigerant flows through
another orifice plate to the evaporator.
Figure 49. Pressure enthalpy curve, 3-stage
P
6
4
High Side Economizer
P
7
3
Low Side Economizer
P
8
2
Evaporator
P
1
1
Enthalpy
Figure 50. Refrigerant flow, 3-stage
CDHH 2-Stage Compressor 1 or 2
Compressed gas from the first-stage impeller is discharged
through the fixed, second-stage variable guide vanes and
into the second-stage impeller. Here, the refrigerant gas is
again compressed, and then discharged into the
condenser. Baffles within the condenser shell distribute the
compressed refrigerant gas evenly across the condenser
tube bundle. Cooling tower water circulated through the
condenser tubes absorbs heat from the refrigerant, causing
it to condense. The liquid refrigerant then passes through
an orifice plate and into the economizer.
The economizer reduces the energy requirements of the
refrigerant cycle by eliminating the need to pass all
gaseous refrigerant through both stages of compression
Condenser
5
Compressor
Third Stage
4
Compressor
Second Stage
3
Compressor
First Stage
2
CDHH-SVX003C-EN
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