Control Logic Operation and Features of ianBMS

Occupancy monitoring

Occupancy is monitored in every supervised space (every room) using motion sensors. The control logic supports up to four motion sensors per room. The outputs of the sensors are ORed together to create the occupied / unoccupied signal for the room. In order to minimize false-negatives, the raw "occupied" signal (coming from the sensors) is prolonged to create three logical occupancy signals per room (short, medium, and long). The "occupied short" signal, once activated, remains so for at least 10 seconds. The "occupied medium" signal, once activated, remains so for at least 15 minutes, and the "occupied long" signal remains activated for at least half an hour. Logic blocks can use the short / medium / long signals as required. The occupancy signals of several rooms are ORed together to create five aggregate occupancy indications: "Front" (for rooms at the front side of the building), "side", "back", "util" (for u tility rooms: kitchen, hallways, restrooms, etc), plus a global "building occupied" signal.

Lighting control

Lights are controlled using bistable (ratchet) relays. A bistable relay is energized to change state from open to closed and vice versa. Once its state changes the relay remains in the new state until it receives the next energization stimulus. One bistable is used for every lighting load (one or more fixtures). The bistables are controlled by the RSC.

Push-buttons are installed to allow the occupants manually toggle the lighting loads (typically one button per load, but more in some spaces like hallways). The push-buttons are connected to controller digital inputs therefore their association to lighting loads can be modified by reconfiguring the controller logic. The occupants can also control the lights though a simple web-based HMI, as well as see the current condition of all the lights in the building.

Apart from manual lights control, the system also provides auto switch-off functionality during after-hours. Auto switch-off will be activated when all three conditions are met:

• It is after 20:00 in the evening and before 08:00 in the morning, or it is a non-working day
• The illuminated space is not occupied, and has remained unoccupied for at least 15 minutes
• The pushbuttons controlling the load have not been pressed for at least 15 minutes
• No HMI command has been issued to turn-on the loads for at least 15 minutes

If no motion sensor is installed in a room, or if a motion sensor is removed or stops to function the system considers the room "always occupied" and acts accordingly.

For some rooms (e.g. rarely visited storage rooms), auto switch-off functionality is enabled during working hours as well. For these rooms, if no motion sensor is present to determine occupancy the lights are switched-off after 15 minutes regardless of occupant presence.

For the restrooms the auto switch-off functionality is also enabled during working hours. The switch-off delay is set to 30minutes (instead of 15).

A global "leave the building" push-button is also provided which, when pressed, switches off all the lights with the exception of the ones illuminating the exit hallway; these are turned on and remain on for 2 minutes permitting the occupant to leave the building.

If controller fails to change the state of a load (fails turn off or on a light), then after 10 retries it declares the bistable relay malfunctioning and raises the respective failure alarm.

Air conditioning

Ceiling mounted fan-coil units are used for air-conditioning the office space. They can operate in three fan speeds (low, medium, high). The temperature in each room will be measured by the controller (using temperature sensors) and the fan-coils will be switched on and off as well as between speeds in order to achieve a set-point. Through the web HMI the occupant will be able to control:

• The speed of the fans. Four options will be given: off, low, med, high, auto.
• The set-point temperature. The occupant will be able to configure the setpoint temperature between 18 and 28 degrees celcius

Regardless of the set-point and fan-speed configured by the occupant, the system will fall-back to a special "unocupied" operating mode when all the following conditions are met:

• It is after 20:00 in the evening and before 08:00 in the morning, or it is a non-working day
• The room is not occupied, and has remained unoccupied for at least 10 minutes

In unoccupied mode a predefined (non occupant-configurable) set-point will be used. With this setpoint---which will be rather low durring heating season, and rather high during cooling season---energy will be conserved when the building is unmanned. Through the web-HMI the occupant will be able to set the room back to normal air-conditioning mode even durring after hours. Once the room is manually set to normal mode, it will remain so for at least 1 hour, then it will switch-back to unoccupied mode provided that the conditions above are still satisfied (i.e. that it is still before 08:00, and the room is still unoccupied).

At 08:00 in the morning the system will enter "boost" mode, whereby the fan-coil unit will operate at full capacity until the occupant-configurable setpoint is reached. Boost-mode helps bring the office-space back to normal temperature quickly.

To better understand the operation of the system consider the following example scenario:

The user has set the fan-speed to "auto", and the setpoint to 22 degC. The administrator has set the unoccupied-mode setpoint to 16 degC. The occupant leaves the room at 19:00, at which point the temperature has been stabilized at the setpoint (22 degC). The room will be kept at this temperature until 20:00 at which time---given that the room is unoccupied and has remained so for more than 10 minutes---the system will set the room to "unoccupied" mode. The fan-coil will be switched-off for the night and will be turned on only if the temperature drops below 16 degC. At 23:00 the occupant enters the room, and using the web HMI sets the air conditioning system back to normal mode. The fan-coil starts operating in order to bring the room temperature back to the setpoint (to 22 degC). The room will remain at "normal" mode for at least 1-hour, even if the occupant departs earlier. While this not the most efficient setting, it limits the reliance on the occupancy sensor and reduces the amount of inconvinience in case of a sensor failure: That is, if the sensor is not working, and the occupant wishes to remain in the building after-hours he has to re-set the system to "normal" mode once every hour. Of course if the sensor is working properly the system will remain in "normal" mode, as long as the occupant is present.

In order to protect the electrical installation from transient over loading, air-conditioning loads will be actuated using "delayed loading" logic than will guarantee a minimum spacing of 5 seconds between to consecutive load activations. This will be especially useful when boost mode is activated in the morning

Server room free cooling

The server room will be cooled by two systems: A split-unit air conditioner, and a free-cooling air exchange system. The air-conditioner will operate autonomously using a constant set-point. The free-cooling system will operate under the control of the RSC. The controller will measure the internal and external temperature and humidity and calculate the respective enthalpy values. If the external enthalpy is lower than the internal enthalpy and the external humidity is lower than a given level, air from outside will be fed to the room by activating the fan of the free-cooling system. Using free cooling the room temperature will be allowed to drop considerably below the air-conditioning set-point, respecting only a failsafe limit. Bringing the server room temperature below the setpoint, will force the air-conditioning system to turn its compressor off, thus conserving energy. The energy consumption of (the current drawn by) both the split unit air-conditioner, as well as the free cooling system will be measured by the controller and logged in order to permit an estimation of the efficiency of the system. The temperature and humidity inside the server room will also be monitored, and logged every 5 minutes. Logs---for temperature and energy consumption---will be held in the controller's memory for one week. Alarms will be generated for high temperature and high humidity inside the server room

Occupancy monitoring

Consumption measurement

Other alarms

Web HMI main screen

• Current room temperature (read only)
• Normal mode temperature-setpoint (configurable)
• Unoccupied mode temperature setpoint (read only)
• Air conditioning unit fan-speed setting (configurable)
• Air conditioning unit actual fan-speed (read only)
• Lights status, and "activate" / "deactivate" commands
• Current occupancy indication
• External temperature
• External humidity
• Smoke detection alarm for server room, kitchen, hardware room, and hallways (3 indications)
• Leak detection alarm for restrooms and kitchen

Switch between heating and cooling

• connect to tel at 192.168.1.8
• change the "SCENACU_000_SEASON" IOB values accordingly (0: winter, 1: summer)