AERMEC MCR Manuel D'utilisation page 33

9 LOCAL NETWORK TTL
The chilled beam thermostat has been designed to be able to manage MCR controller networks via a dedicated serial port based on TTL logic standards and low throughput
(amount of data transmitted in a unit of time).
This serial communication is indispensable for the exchange of information between chilled beams installed in the same area, which for system reasons requires several hy-
dronic units. We are talking about a network of a maximum of 6 units and a maximum length of approximately 30 metres.
Specifically in this network there is always a master to which the VMF-E4X/VMF-E3/VMHI user interface is connected, which controls the operation of the slaves connected to
it, based on the settings made on its user interface.
Max 30m
MODBUS TTL
MASTER SLAVE 1 SLAVE 6
VMF-E4X
FUNCTIONING PRINCIPLE
The master cold beam, i.e. the one connected to the user interface, cyclically transmits to the slave units and sets the following information on them:
— Control setpoint
— Operation mode (OFF, AUTO, V1, V2, V3, AUX)
— Operating season
Therefore, slave units cannot operate (except in special cases) according to settings other than those dictated by the master.
Room probe: The room control probe is not required on slave chilled beams as these can use the master's control probe, if any. However, if you want to avoid microclimates,
it can also be installed on the slaves, which will then be regulated with the respective probe. In the particular case in which the room sensor fails on the master, the slaves not
equipped with a sensor will operate in emergency mode (like the master) while the slaves equipped with a room sensor will continue to operate in normal mode.
Water probe: The water probe may or may not be installed on the chilled beams of the TTL network. Units equipped with a probe can use it for the minimum and maximum
checks required.
Humidity probe: As with the air probe, the humidity probe is not required on all chilled beams. Slave units can receive the data read by the master.
External Contact Input (DI1): This digital input is enabled on all units and maintains the intended operation.
Presence sensor input (DI2): the presence sensor digital input is only active on the master beam which uses this to determine, as explained in the "Sleep function" paragraph,
the value of the adjustment setpoint which will then be sent to the slaves.
Antifreeze function: Antifreeze mode is the only case in which a slave in this state can operate according to settings not foreseen by the master. In general, chilled beams,
regardless of whether they are masters or slaves, when they enter frost protection mode, they begin to operate as described above in the "Frost protection" section.
FAULTS ON THE TTL NETWORK
No Master-Slave Communication: Slave units cyclically expect zone settings from the master. If a slave no longer communicates with the master for any reason, it goes into
OFF status (i.e. all loads are switched off) 10" after the last command is correctly received.
No Master-User Interface Communication: If the master finds itself at some point no longer communicating with the user interface, it goes into OFF status 30" after the last
command received from the user interface. The master will also send the OFF command to all slaves.
TTL NETWORK CONSTRAINTS
The constraint relates to the management of the control dead zone, which in fact only needs to be set on the master controller as it is ignored on the slaves since both the
setpoint and the operating season of these depend on the master.
22/04 – 5572952_00 33