4.6 - Actuators
■
Electronic Expansion Valve:
The electronic expansion valve
(EXV) is used to adjust the refrigerant flow to changes in the
operating conditions of the machine. The high degree of
accuracy with which the piston is positioned provides precise
control of the refrigerant flow and suction superheat.
■
Staging valve:
The staging valve is used during the start of
the compressor to route its flow through a bypass and to enable
the compressor start in proper conditions.
■
Evaporator flow switch:
A flow switch is mounted to ensure
that the minimum flow rate required for the correct operation and
protection of the system is maintained. If the flow switch fails, the
alarm condition shuts off the unit. The flow switch can also be
added in the condenser exchanger (not provided with the unit).
■
Variable-speed water pumps:
The controller provides a
command of speed for the evaporator water loop. The water
flow control is based on the heat exchanger temperature
difference.
■
Water pumps (optional):
The unit can be fitted with one
evaporator and one condenser pump. The controller can
independently regulate each water heat exchanger pump.
4.7 - Terminal block connections
The “Terminal block connections” table given below summarizes
connections at the user terminal block. Connections available at
the user terminal block may vary depending on the selected options.
IMPORTANT: Some contacts can be accessed only when the
unit operates in Remote mode.
4.7.1 - Volt-free contact (on/off and cool/heat)
Contact
Off
Cooling
Heating
On/Off switch
open
closed
closed
Heat/Cool switch
open
open
closed
4.7.2 - Volt-free setpoint selection contact
When the unit is under remote control, the volt-free contact is used
to determine the active setpoint. This dry contact is used to switch
between setpoints.
Contact
Setpoint 1
Setpoint 2
Setpoint 3
Setpoint switch
open
closed
closed
* Ice done contact must be open to enable “setpoint 3”
4.7.3 - Volt-free demand limit selection contact
Two dry contacts can be used to limit unit capacity.
Contact
100%
Limit 1
[lim_sp1]
Limit 2
[lim_sp2]
Limit 3
[lim_sp3]
Demand limit switch #1
open
closed
open
closed
Demand limit switch #2
open
open
closed
closed
4 - HARDWARE DESCRIPTION
Terminal block connections
Description
Board
Connector
Remarks
On/Off switch
SIOB #1
DI-01, 32-33
Used for the unit on/off control (Remote mode only):
open = unit is Off
closed = unit is on
Heat/Cool Switch
SIOB #1
DI-02, 63-64
Used to switch between heating and cooling (Remote mode only)
Demand Limit Switch #1
SIOB #1
DI-03, 73-74
Used to control demand limit:
open = 100% capacity can be used, no demand limitation is applied
closed = demand limitation applied
Customer interlock
SIOB #1
DI-04, 34-35
- Bypass
Used to control unit start/stop:
open = unit shuts down
closed = unit is allowed to operate
Setpoint Switch
SIOB #1
DI-05, 65-66
When the unit is under remote control, the volt-free contact is used to
determine the active setpoint (see section 8.4.1)
Setpoint reset
SIOB #1
AI-10, 71-72
4-20 mA signal to offset the active setpoint of the unit
Alarm relay *
SIOB #1
DO-05, 30A-31A
Used to signal an alarm:
open = inactive (no alarms active)
closed = alarm(s) active
Running Relay
SIOB #1
DO-06, 37-38
Used to signal a running status (at least one compressor start)
External Pump Speed Command
of the evaporator
SIOB #1
AO-01, 90+ 90 -
Used to control the speed of a pump by a 0-10V signal
3-way valve control
AUX1 #1
Ch 9, 80+ 80-
Used to control a three way valve on the condenser water loop (optional)
Occupied Override Switch
SIOB #3
DI-01, 77-78
In Remote mode closing this switch set occupancy to "yes"
Demand Limit Switch #2
SIOB #3
DI-02, 73A-74A
In remote mode enables the 2nd capacity limit setpoint
Ice setpoint
SIOB #3
DI-03, 75-76
Closing this input disables the ice setpoint
Condenser flow switch
SIOB #3
DI-05, 96-97
- Bypass
Used to detect the flow on the condenser side. It should be closed to
authorise the unit to start
Space temperature for reset
control
SIOB #3
AI-01, 71A-72A
Space temperature for reset control
Capacity limit control
SIOB #3
AI-10, 67-68
4-20 mA signal to set the demand limit of the unit
Chiller Alert state *
SIOB #3
DO-05, 30B-31B
Closed if an alert is present
Chiller shutdown state *
SIOB #3
DO-06, 30-31
Closed if chiller is shutdown
Chiller capacity running output
(0 to 10V)
SIOB #3
AO-01, 79+ 79-
Used to transmit the voltage level corresponding to unit production
(10V = production at full capacity)
* These signals can be reversed by setting the parameter al_rever to “yes” in the GEN_CONF table.
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