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11 - MAJOR SYSTEM COMPONENTS AND OPERATION DATA
Corrosion allowances:
Gas side: 0 mm
Heat exchange fluid side: 1 mm for tubular plates in lightly alloyed
steels, 0 mm for stainless steel plates or plates with copper-nickel
or stainless steel protection.
11.2.1 - Evaporator
19PV chillers use a flooded multi-tube evaporator. The water
circulates in the tubes and the refrigerant is on the outside in the
shell. One vessel is used to serve both refrigerant circuits. There
is a centre tube sheet which separates the two refrigerant circuits.
The tubes are 3/4" diameter copper with an enhanced surface inside
and out. There is just one water circuit with two water passes (one
pass with Evaporator with option 100C, please refer to chapter 6.5).
The evaporator shell has a polyurethane foam thermal insulation
and a water drain and purge.
It has been tested and stamped in accordance with the applicable
pressure codes. The maximum standard relative operating pressure
is 1850kPa for the refrigerant-side and 1000 kPa for the water-side.
These pressures can be different depending on the code applied.
The water connection of the heat exchanger is a Victaulic
connection.
The products that may be added for thermal insulation of the
containers during the water piping connection procedure must be
chemically neutral in relation to the materials and coatings to which
they are applied. This is also the case for the products originally
supplied by the manufacturer.
11.2.2 - Condenser
The 19PV chiller uses a flooded multi-tube condenser. It is mounted
below the evaporator. The water circulates in the tubes and the
refrigerant is on the outside in the shell. One vessel is used to
serve both refrigerant circuits. There is a center tube sheet which
separates the two refrigerant circuits. The tubes are 3/4" or 1"
diameter internally and externally finned copper tubes.
There is just one water circuit with two water passes (one pass
with Condenser with option 102C, please refer to chapter 6.5).
For the Heat Machine units the condenser shell can have a polyure-
thane foam thermal insulation (Option 86 or 322) and a water drain
and purge.
It has been tested and stamped in accordance with applicable
pressure codes. The maximum standard relative operating pressure
is 1850kPa for the refrigerant-side and 1000 kPa for the water-side.
These pressures can be different depending on the code applied.
The water connection of the heat exchanger is a Victaulic
connection.
11.3 - Disconnect switches for power supply
Each circuit includes two disconnect switches: One main supply
disconnect switch for the compressor(s) supply and one disconnect
switch associated with a handle for the supply of the control part,
the under-voltage protection circuit and the motor mechanism
module.
The motor mechanism module and an under-voltage protection
circuit are mounted on the main supply disconnect switch.
Note: The following procedure must be done to lock the main
supply disconnect switch:
- Set the motor mechanism in "Manual" position. The circuit
breaker must be to the O (OFF) position before this operation.
- Pull up the locking tab.
- Lock the circuit breaker using the keylock (leaving the tab out).
After removing the lock, the motor mechanism must be switch in
"Auto" position before to supply the unit.
The command of the main supply disconnect switch closure is
ensured by the software using the motor mechanism module when
the unit is turned on (with the handle) or when the voltage is back
after the loss of the power supply.
The under-voltage protection circuit ensures the main supply
disconnect switch opening in case of a turn off (using the handle
from the front panel), a high-pressure safety switch opening or
when the doors is open.
The downstream circuit of the disconnect switch with the handle
is consider as an excepted circuit and is identified with orange
conductors.
11.3.1 - Safety chain of the automatic reset
11.3.1.a - High-pressure switch HP
19PV units are equipped with high-pressure safety switches.
In accordance with the applicable code , the unit is equipped with high
pressure switches with manual reset, called PZH (former DBK).
These pressure switches are located at the discharge line of each
compressor.
11.3.1.b - Safety door contacts
The purpose of the door contact is to inhibite the possibility of an
automatic closure order of the main supply disconnect switch from
the software while the door is opened
11.4
Electronic expansion valve (EXV)
The 19PV unit is equipped with two EXV :
- The main EXV located in the liquid line. The main EXV
regulates refrigerant flow into the evaporator.
- The staging EXV located in the discharge line. The staging
EXV regulates by-pass flow during compressor stat-up.
The EXV is equipped with a stepper motor 480 steps that is
controlled via the EXV board.
The EXV is also equipped with a sightglass that permits verification
of the mechanism movement and the presence of the liquid gasket
(Relevant only for main EXV).
11.5 - Moisture indicator
Located on the EXV and on the compressor cooling line, permits
control of the unit charge and indicates moisture in the circuit. The
presence of bubbles in the sight-glass indicates an insufficient
charge or non-condensables in the system. The presence of
moisture changes the colour of the indicator paper in the sight-
glass.
11.6 - Filter drier
The role of the filter drier is to keep the circuit clean and moisture-
free. The moisture indicator shows, when it is necessary to change
the element. A difference in temperature between the filter inlet
and outlet shows that the element is dirty.
11.7 - Sensors
The units use thermistors to measure the temperature, and
pressure transducers to control and regulate system operation
(see 19PV Touch'Pilot Control manual for a more detailed
explanation).
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