A wireless BAS sensor is worth specifying on a retrofit when running new wire—through finished walls, occupied spaces, or across a slab—is the costly part of the job. But what ultimately makes the decision is whether the device holds up after it's installed, meaning it has a reliable signal and no maintenance to schedule. A building automation system (BAS) sensor that harvests its own power answers the maintenance half directly, because there is no battery to replace.
Functional Devices, Inc. manufactures EnOcean wireless devices for building automation, including self-powered sensors and switches that operate without batteries.
Why Wireless Makes Sense for a Retrofit
On a retrofit, the cost and disruption are usually caused by the conduit and the labor required to pull cable through a finished building, not by the installation of the device itself. A wireless sensor or switch mounts where it's needed and sends its signal to a receiver. This means it can be deployed in places where running cable is difficult or expensive: existing walls and ceilings, tenant spaces that can't be opened up, points added to a system after the wire is already in, or switch locations that move.
What Powers a Wireless Sensor: Batteries or Energy Harvesting
A battery-powered sensor carries its own cell. It works anywhere, but the battery is a maintenance item: it has a service life, and it has to be tracked and replaced. Across a building of sensors, that can become costly, both in terms of budget and time.
A self-powered sensor harvests the energy it needs from its surroundings: a switch press, ambient light, or a temperature difference. EnOcean, the energy-harvesting wireless standard these devices use, is built around this. A wall-switch transmitter converts the force of the press into enough energy to send its signal, so there is no battery and nothing to replace.
For a retrofit, the self-powered approach removes the maintenance question that makes facilities teams wary of wireless. The receivers that the sensors talk to are line-powered, because they switch loads and need power anyway, so a system built this way has no batteries in it at all.
What Makes a Wireless BAS Sensor Reliable
Reliability on a wireless sensor is a question of whether the signal reaches the receiver every time. A few things determine that.
- Range. A typical EnOcean transmitter reaches a receiver at roughly 50 to 150 feet indoors, and farther in open air. Walls, floors, and metal between the transmitter and receiver cut that distance, so the figure is a planning starting point, not a guarantee.
- Repeaters. Receivers in this line double as repeaters: a receiver can rebroadcast a signal to the next one, which is how coverage reaches across a building.
- Frequency. These devices operate at 902 MHz, a sub-GHz band that passes through typical building construction better than the 2.4 GHz used by Wi-Fi and Bluetooth.
- Linking. A single receiver can be linked to several transmitters, so a group of switches or sensors can drive one relay. Map which transmitters go to which receivers before mounting anything.
Integrating Wireless Sensors with the BAS
A wireless signal has to become something the rest of the system can use. The transmitter sends to a line-powered receiver relay, and the relay is where the signal becomes a physical action or a point the controller can read.
A receiver relay can switch a load directly (lighting, a fan, a damper) on a signal from a wireless switch or sensor. Models with a dry-contact input or a 0–10 Vdc analog output can also pass a status or a level to a building controller, which is how a wireless point reaches the BAS. For bidirectional links into a larger system, a gateway controller pairs with the relays.
Because the receiver relays are line-powered and mounted at the load or the panel, the wireless part of the system is limited to the sensor-to-receiver hop. The wired BAS picks up from the receiver.
Functional Devices EnOcean Wireless Devices
Functional Devices manufactures both halves of an EnOcean system: self-powered transmitters and line-powered receiver relays.
- The WWS2-EN3 is a self-powered wireless wall switch, powered by the press of its rocker, that controls a load or a group of loads within range of a receiver.
- The FDLTVC is a self-powered EnOcean occupancy and vacancy sensor, ceiling-mounted, for lighting control.
- The RIBW277B-EN3 and RIBW240B-EN3 are wireless relays (transceiver and repeater, 20 A SPDT, dry-contact input) at 277 and 240 Vac.
- The RIBW21BAO-EN3 is a wireless relay (transceiver and repeater, 20 A SPDT, 120–277 Vac) with a 0–10 Vdc analog output for passing a level to a controller.
- The FDLR05B and RIBW01C-EN3 are receiver and repeater relays (5 A SPST-N/O, 120 Vac) for lighting loads.
The transmitters run without batteries; the relays use line power because they switch loads. Functional Devices also makes the relays, current sensors, and power supplies used elsewhere in the same panel.
Frequently Asked Questions
Do wireless BAS sensors need batteries?
Not if they are self-powered. EnOcean sensors and switches harvest the energy they need from a switch press, light, or a temperature difference, so there is no battery to replace. The receivers they communicate with are line-powered.
How far can a wireless BAS sensor transmit?
Roughly 50 to 150 feet indoors for a typical EnOcean transmitter, and farther in open air. Walls, floors, and metal shorten that, and a receiver can act as a repeater to extend coverage.
How do wireless sensors connect to the building automation system?
The sensor or switch transmits to a line-powered receiver relay. The relay switches a load directly, or passes a dry contact or 0–10 Vdc output to a building controller, which is how the point reaches the BAS.
Are wireless sensors reliable enough for a retrofit?
Yes, when the layout is planned for range. Keep each transmitter within range of a receiver, use repeaters across longer distances, and account for the walls and metal that cut signal.
Specify Wireless BAS Devices for a Retrofit
To match wireless sensors and receivers to a retrofit, contact Functional Devices at 800-888-5538, or find an authorized distributor in your region.