• Great comfort and control for end user
  • Ease of data monitoring assists the Building Manager
  • Simplified & low cost installation for Systems Integrator 

Making sense of smart buildings

 

Over the last few years, talk of smart buildings has become commonplace. But what defines a smart building? Martin Schreiber, Product Manager at Sontay, explores the fundamental requirements for a smart building and the role of sensors in making them a reality.     

What is smart and what is a smart building? According to the 2nd Technical Support Study on the Smart Readiness Indicator (SRI) For Buildings report*, the working-definition of the smartness of a building refers to “the ability of a building or its systems to sense, interpret, communicate and actively respond in an efficient manner to changing conditions in relation to the operation of technical building systems or the external environment (including energy grids) and to demands from building occupants.” 

The key word that stands out for me in this explanation is ‘sense’. A smart building would be nothing without the variety of sensors that monitor and analyse environmental conditions on a day to day basis, then provide that information to the building control system. Sensors are constantly working, providing valuable data back to the control system but how can they help create smarter buildings? 

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Technical Q&A

Is it possible to make them IP and POE .. 

Yes, by using our range of cost efficient and easy to install BACnet Routers. In a building automation system equipment on the device level is typically wired using a low cost 2-wire databus. On the management level the segments connected using Ethernet. The BACnet Routers require external power supply and don't support POE. 

Do you need a separate cable for power supply? 

Sensors can be connected by one cable as long as the PS and data are connected via different cores. Consequently a 4 core cable is needed, 2 cores for power supply and 2 cores for data.

How much current do they draw? 

The current drawn by the sensor depends on which features are ordered/enabled and which source power supply is used. For examples if the sensor has CO2 and LCD then it will draw 377mA (24Vdc) whereas when it senses temperature and relative humidity only then it will only draw 15mA (24Vdc). On our datasheet we specify the worst case scenario when powered in 24Vdc. 

How many can you have on one network? 

As a rule, the RS-485 wiring standards apply. With regards to BACnet MS/TP we recommend that you connect no more than 32 devices per MS/TP segment. This number can be increased depending on what baud rate, bus length and loading factor is used. For device numbers between 32 and 64, the network should be split in two segments of up to 32 each connected to BACnet Routers. Please refer to RS-485 wiring guidelines. 

Do I need a separate power supply for the outputs? 

If the sensor is powered with a 24Vac supply, the DO's can be switched to the 24VAc supply and there is no need for a separate supply. 

If the sensor is powered with a 24Vdc supply, the DO's require a separate 24Vdc supply for the loads to be switched. 

What happens when there is a break in the networking? Does this make every sensor go down? What are the implications of this happening? 

That depends on the failure mode. Typically the devices downstream from the break are offline and everything connected upstream will still function. Splitting parts of the network in half can help to locate the issue in case the entire network is down. 

What values are displayed on the LCD screen? 

That depends on the failure mode. Typically the devices downstream from the break are offline and everything connected upstream will still function. Splitting parts of the network in half can help to locate the issue in case the entire network is down. 

What values are displayed on the LCD screen? 

The LCD can display any configured sensor data: Temp+ RH, Temp+ RH+ CO2, Temp+ RH+ TVOC . There are 16 different LCD modes, these are described in a PDF document. 

Is it certified EU.BAC? 

A sensor on its own cannot be certified. It can only be certified as part of a system. 

Can the Input be configured?

Yes, 0-l0V or 10K3AI.

Smart Sensor Application Brochure

Technical datasheets

SC-S Smart Sensor Space Mounted (2.0 MB)

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SC-x Smart Sensor Plant Mounted (2.2 MB)

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SC-x Smart Sensor BACnet PICS and Modbus registers (3.4 MB)

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