CVHH-SVX001A-EN
67
Operating Principles
General Requirements
Operation and m aintenance inform ation for CVHH chillers
are covered in this section. This includes both 50 and 60 Hz
centrifugal chillers equipped w ith the Tracer AdaptiView
UC800 control system . This inform ation pertains to all
chiller types unless differences exist, in w hich case the
sections are listed by chiller type as applicable and
described separately. By carefully review ing this
inform ation and follow ing the instructions given, the
ow ner or operator can successfully operate and m aintain
a CenTraVac unit. If m echanical problem s do occur,
how ever, contact a Trane service technician to ensure
proper diagnosis and repair of the unit.
Cooling Cycle
When in the cooling m ode, liquid refrigerant is distributed
along the length of the evaporator and sprayed through
sm all holes in a distributor (i.e., running the entire length
of the shell) to uniform ly 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 draw n through
the elim inators (w hich rem ove droplets of liquid
refrigerant from the gas) and the first stage variable inlet
guide vanes, and into the first-stage im peller.
CVHH 3-Stage Compressor
Com pressed gas from the first-stage im peller flow s
through the fixed, second-stage inlet vanes and into the
second-stage im peller. Here, the refrigerant gas is again
com pressed, and then discharged through the third-stage
variable guide vanes and into the third-stage im peller.
Once the gas is com pressed a third tim e, it is discharged
into the condenser. Baffles w ithin the condenser shell
distribute the com pressed refrigerant gas evenly across
the condenser tube bundle. Cooling tow er 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
econom izer.
The econom izer reduces the energy requirem ents of the
refrigerant cycle by elim inating the need to pass all
gaseous refrigerant through three stages of com pression
(see
Figure 35, p. 67
). Notice that som e of the liquid
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 draw n directly from the
first and second stages of the econom izer into the third-
and second-stage im pellers of the com pressor,
respectively. All rem aining liquid refrigerant flow s
through another orifice plate to the evaporator.
CVHH 2-Stage Compressor
Com pressed gas from the first-stage im peller is
discharged through the second-stage variable guide
vanes and into the second-stage im peller. Here, the
refrigerant gas is again com pressed, and then discharged
into the condenser. Baffles w ithin the condenser shell
distribute the com pressed refrigerant gas evenly across
the condenser tube bundle. Cooling tow er water,
circulated through the condenser tubes, absorbs heat
from the refrigerant, causing it to condense. The liquid
refrigerant then flow s out of the bottom of the condenser,
passing through an orifice plate and into the econom izer.
The econom izer reduces the energy requirem ents of the
refrigerant cycle by elim inating the need to pass all
gaseous refrigerant through both stages of com pression
(see
Figure 37
). Notice that som e of the liquid refrigerant
flashes to a gas because of the pressure drop created by
the orifice plate, thus further cooling the liquid refrigerant.
This flash gas is then draw n directly from the econom izer
into the second-stage im pellers of the com pressor. All
rem aining liquid refrigerant flow s out of the econom izer,
passes through another orifice plate and into the
evaporator.
Figure 34.
Pressure enthalpy curve, 3-stage
Figure 35.
Refrigerant flow, 3-stage
condenser
high side econom izer
evaporat or
2
3
4
P
1
P
3
P
2
P
4
P
re
s
s
u
re
com pr essor
( 3
rd
st age)
low side econom izer
com pr essor
( 2
nd
st age)
com pr essor
( 1
st
st age)
5
6
7
8
1
Summary of Contents for CVHH
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