Two pipe systems feature a single valve actuator to control the water inlet to an exchanger. In this type of installation all zones are either on “Cool” mode or “Warm” mode, since there are only 2 pipes (supply/return) through which either warm or cool water circulates. Warm or cool water supply to the circuit is determined by a decision based on various weather parameters, or it will be set by the individual in charge of the facility.
This device is designed to work as a stand-alone element; however, it includes a standard EN14908 LonWorks communication bus that enables remote communication with a BMS (Building Management System) in order to remotely control all its parameters and provide room status data such as temperature, setpoint, occupancy status, etc.
In this Application Note, device inputs and outputs are configured as follows:
• Card reader contact input: connected to the room card reader. When the card is inserted, the courtesy light comes ON during a period of time that is preset through a configuration variable and HVAC operation is enabled. When the card is removed, the courtesy light comes ON during the same preset period and HVAC operation is automatically disabled. At this point, the device status is modified to indicate that the zone becomes unoccupied.
• Window contact input: connected to a window magnetic switch in the room. When the window is opened, the HVAC power is disconnected. When it is closed again, HVAC is restored.
• Water sensor input: not used for this Application Note.
• External temperature input: not used for this Application Note.
• Fan coil speed outputs (I-II-III): connected to the fan coil to control fan coil operating speed. If the device is in AUTO mode, fan speed is automatically controlled, based on temperature and the user-defined setpoint.
• Valve actuator output: connected to the valve actuator. The device activates and stops this output, based on zone climate demand. It activates when the device requests climate control and it stops when the device reaches the required temperature.
• AUX output: connected to the courtesy light. It activates when the card is either inserted or removed. The output remains active during a “t” period of time, which is preset by the installer.