Electronic Expansion Valve (Exv); Moisture Indicator; Filter Drier; Sensors - Carrier AQUAFORCE 30XW Series Installation, Operation And Maintenance Instructions

12 - MAJOR SYSTEM COMPONENTS AND OPERATION DATA
12.2.2 - Condenser and oil separator
The 30XW chiller uses a heat exchanger that is a combination
condenser and oil separator. It is mounted below the evaporator.
Discharge gas leaves the compressor and flows through an
external muffler to the oil separator, which is the upper portion of
the heat exchanger. It enters the top of the separator where oil is
removed, and then flows to the bottom portion of the vessel, where
gas is condensed and subcooled. 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 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) 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 2100 kPa 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.
12.2.3 - Economiser function (depending on model)
The economiser function includes a liquid line valve, a filter drier,
two electronic expansion valves (EXVs), a plate heat exchanger
as well as protection devices (fuse or valve).
At the condenser outlet a part of the liquid is expanded via the
secondary EXV in one of the heat exchanger circuits and then
returns as a gas. This expansion permits increase of the liquid
sub-cooling of the rest of the flow that pene-trates the evaporator
via the principal EXV. This permits increasing the cooling capacity
of the system as well as its efficiency.

12.3 - Electronic expansion valve (EXV)

The EXV is equipped with a stepper motor (2785 to 3690 steps,
depending on the model) 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.

12.4 - Moisture indicator

Located on the EXV, 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-con-densables
in the system. The presence of moisture changes the colour of
the indicator paper in the sight-glass.

12.5 - 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 tempera-ture between the filter inlet
and outlet shows that the element is dirty.

12.6 - Sensors

The units use thermistors to measure the temperature, and
pressure transducers to control and regulate system opera-tion
(see SmartVu Control IOM for a more detailed explanation).
TM
40

12.7 - SRMCR high-pressure safety circuit

General description
The device is equipped with a high pressure safety loop, also
known as safety related measurement control and regulation
system (SRMCR), consisting of:
■ 2 high pressure switches (HPS) with manual reset located at
the outlet of each compressor:
- A pressure switch type PZH
- A pressure switch type PZHH
■ A control relay on the compressor board
■ 2 compressor main contactors
See the wiring diagram and bill of material of the unit for details
of identification and references.
This safety loop is designed according to EN 61508 for:
SIL level (Safety Integrity): 2
Demand mode: high and low
Mission Time: 20 years.
Periodic test: The safety loop operation must be tested at least
once a year to maintain its integrity.
Function description and reset:
Diagram below describes the description of operation: refer to the
machine documentation to obtain the detailed wiring diagram
Normal
Start-stop
CR1
Logic
Normal
Start-stop
Normal
Start-stop
Compressor A_C board
HPS : High Pressure Swich
CR : Relay with dry contact
KM : Power contactors
_ : Circuit designation (1 or 2)
: Parts of the SRMCR
The HPS switches are wired in series to the control relays of the
A_C board which controls the KM and KM-D main contactors.
Both switches are closed during continuous operation of the
compressor. When one of the HPS switches opens, the control
relay interrupts the supply voltage of the KM-and KM-D contactor
coil: the main contactor opens, which causes the compressor to
lose power and stop.
The operation of this safety loop is electromechanical: it is not
based on software or an electronic component.
HPS SP_F
HPS SP_F
(115Vac)
CR2
KM_D
KM_Y
400Vac
KM_D
Compressor
06T
KM_
400Vac
0v