The Russian company Systeme Electric has introduced a series of digital thermostats SystemeRT RTF for regulating room temperature in heating, ventilation and air conditioning (HVAC) systems equipped with 2- and 4-pipe fan coils and valves (2-position and with 0…10 V DC actuators). These digital room thermostats are easy to install, connect and use, do not require programming, and models with an RS-485 interface support integration into BMS building management systems via the Modbus RTU protocol. The design of the new products includes an air temperature sensor, a backlit LCD menu screen and 5 buttons, with which you can set the required operating modes of the climate control equipment.
SystemeRT digital thermostats of the RTF type are designed for flush-mounted wall mounting at a height convenient for viewing and control - 1.2-1.5 m from the floor. For the digital room thermostat to work correctly, there should be no obstructions to air circulation, heat sources such as radiators and air curtains, and direct sunlight, since it is equipped with a built-in temperature sensor. If necessary, the digital thermostat can be supplemented with a remote temperature sensor with an NTC 10 kOhm output (option not available for all models), for example, a wall-mounted Systeme Electric SRTN or SDTN, installed in the exhaust air duct.
The climate control equipment is intuitive and is controlled using the buttons on the front panel of the thermostat. Along with the on/off button, the digital room thermostat is equipped with a button for going to the menu for selecting the operating mode and fan speed, and the menu is navigated using the up and down buttons. SystemeRT RTF supports operation in cooling, heating and ventilation modes, and thermostats for controlling the RTF4xx 4-pipe fan coil also support automatic mode. It is worth noting that to prevent unauthorized changes to the current settings, the thermostat buttons can be locked, which is convenient when using it, for example, in public spaces.
Integration into the automated building management system BMS (Building Management System) is available for digital thermostats that support connection to the RS-485 data bus and is performed using the Modbus RTU protocol. In this case, the digital room thermostat acts as a Modbus RTU Slave. To connect the thermostat to the system, it is recommended to use a cable specialized for RS-485, observe the loop topology and install 120 Ohm terminators at the ends of the line, and to protect against interference, use a shielded cable with a connection to the low-current ground bus at one point, for example, in the controller cabinet.
Connection of additional equipment, such as a card switch or another switch, via a "dry contact" is available optionally for SystemeRT RTF digital thermostat models with the "I" index in the name. For example, using a card switch allows you to switch the digital room thermostat to a previously set mode when inserting a card into the card reader, without entering the device menu. When removing the card from the card reader, the thermostat switches to an economical operating mode: the cooling mode setting increases to 26 °C, the heating mode setting decreases to 18 °C, the control buttons are disabled.