7
4.1 - Control boards
All boards making up the Touch Pilot Junior control
system are installed inside the electrical cabinet. They
communicate via an internal LEN bus.
The system may embrace up to two SIOB boards, where the
first board is used to manage all major inputs and outputs of
the controller, whereas the second SIOB board is used to
support either the compressor of circuit A or circuit B.
The first SIOB board is also referred to as the main board
– the main board continuously monitors the information
received from various pressure and temperature probes
and accordingly starts the program that controls the unit.
At the same time, up to two (2) AUX1 boards can be
installed. The first AUX1 board may provide additional
inputs and outputs used to monitor chiller water system
cooling temperature (Master/Slave assembly), leakage
charge detection readings, electric heating or boiler
operation. This board is used only for smaller units (units
with only one fan) that have any of the aforementioned
options available (electric heaters, boiler, etc.).
The second AUX1 board is optional and it is used for units
with the dry cooler option. It provides information
required to control the free cooling cycle.
4.2 - Electrical box
The electrical box includes all boards controlling the unit
and the user interface (
Touch Pilot Junior
).
4.3 - Power supply to boards
All boards are supplied from a common 24 VAC supply
referred to earth.
In the event of a power supply interrupt, the unit restarts
automatically without the need for an external command.
However, any faults active when the supply is interrupted
are saved and may in certain cases prevent a given circuit
or the unit from restarting.
CAUTION
Maintain correct polarity when connecting the power supply
to the boards, otherwise the boards may be damaged.
4.4 - Light emitting diodes
All boards continuously check and indicate the proper
operation of their electronic circuits. A light emitting diode
(LED) lights on each board when it is operating properly.
•
The red LED flashing for a two-second period
indicates correct operation. A different rate indicates
a board or a software failure.
•
The green LED flashes continuously on all boards to show
that the board is communicating correctly over its internal
bus (LEN bus). If the green LED is not flashing, this
indicates a LEN bus wiring problem or a configuration issue.
4 - HARDWARE
4.5 - Pressure transducers
Three types of transducers (high pressure, low pressure,
water pressure) are used to measure various pressures in
each circuit. These transducers deliver 0 to 5 VDC. They
are connected to the SIOB board.
Discharge pressure transducers (high pressure type)
These transducers measure the discharge pressure in each
circuit. They are used to control condensing pressure or
high pressure load shedding. Discharge pressure sensors
are mounted on the discharge line piping of each circuit.
Suction pressure transducers (low pressure type)
These transducers measure the suction pressure in each
circuit. They are used to control EXV, evaporating
pressure (in heating mode) and monitor suction pressure
safeties related to the compressor operating envelope.
Suction pressure sensors are located on the common
suction piping of each circuit.
Pump inlet/outlet water pressure transducers
(water pressure type, hydronic kit option)
These transducers measure the hydronic kit pump water
inlet/outlet water pressure and monitor the water flow.
Pump inlet/outlet water pressure sensors are mounted on
the optional hydronic kit.
4.6 - Temperature sensors
Temperature sensors constantly measure the temperature
of various components of the unit, ensuring the correct
operation of the system.
Water heat exchanger entering and leaving water
temperature sensors
The water heat exchanger entering and leaving water
temperature sensors are used for capacity control and
safety purposes.
Outdoor air temperature sensor
This sensor measuring the outdoor air temperature is used
for start-up, setpoint temperature reset and frost control.
Suction gas temperature sensors
These sensors measure the suction gas temperature. They
are used for the EXV control. Suction gas temperature
sensors are located at the suction side of each circuit.
Master/slave water sensor (optional)
This sensor measures the common water temperature in
the master/slave system capacity control. It is installed only
in the case of master/slave units.
Defrost temperature sensors (heat pumps)
These sensors are used to determine the end of the defrost
cycle for a given circuit.