As the IoT revolution gains momentum with building systems becoming more integrated across LANs, WANs, and the Internet, Building Automation is heading full tilt towards the convergence of BACnet communication protocols with IT network structures. The steady growth of BACnet/IP controller options introduces a new dynamic between BAS and IT, resulting in one of the interesting challenges facing projects today. This includes the introduction of BACnet SC.
The main benefits of BACnet/IP lay in vastly increased data communication speed, ease of scalability and ability to troubleshoot errors efficiently. While the benefits of BACnet/IP outweigh the risks, they need to be balanced with the security concerns of IT. Let’s take a look at some Do’s and Don’ts of BACnet/IP in BAS design and implementation.
Do’s of BACnet/IP System Design and Implementation
1. Start discussions between the BAS contractor and IT group very early in a project and adhere strictly to the customer’s desires in network infrastructure and security.
Different customers have different requirements and expectations of network security: some are happy to provide IP addresses on their in-house business networks and allow the BAS contractor to provide their own network switches, where others want the BAS system to be entirely separate from the in-house networks for security purposes. These all have impacts on what devices are provided, where they are installed, and how the network is physically laid out. Because there is massive flexibility in how IP networks can be constructed, it is important that everyone is on the same page, ensuring that there are no security issues on the customer’s end and no network communications issues on the BAS end.
2. Consider installation for communications integrity and redundancy.
Ring topologies, where a set of controllers are connected via CAT5 or CAT6 cables in a loop back to a managed ethernet switch, provide network redundancy in the event that a wire is cut, damaged, or a controller is removed entirely. Early discussions during the design phase of a project will ensure you have the most robust system.
Don'ts of BACnet/IP System Design and Implementation
1. Don’t install controllers beyond their maximum allowable distance.
Installation of BACnet/IP controllers, while more flexible in many regards, has distance limitations compared to serial communications. Ethernet runs are not recommended to extend beyond 300 meters. This can be avoided with clever network layout or remedied with fiber to ethernet media converters, but it’s a design consideration that wasn’t previously much of a concern with serial communications.
2. Not considering network switches in system design.
Systems with BACnet/IP capable controllers will require many more network switches in most cases. There are also more configuration parameters to keep track of with IP controllers compared to serial. Serial devices have physical switches on them to set their MAC address that can be set with a screwdriver, where IP devices require connection via a computer to configure the IP address and other communication parameters. Checking to make sure that the switches are capable of the network topology of design (daisy chain by default or RSTP / Ring) in the beginning stages can better eliminate surprises during the subsequent construction phase.
In which applications are controllers capable of BACnet/IP an ideal solution?
BACnet/IP controllers are particularly ideal in any new construction where network topology can be planned ahead, but that doesn’t totally rule them out of retrofit work either.
BACnet/IP controllers are advantageous also in small applications. A smaller single system added to a new building can be controlled with just an IP based controller, compared to the previous configuration that included an IP based router that then connected via BACnet/ARCnet or BACnet/MSTP to an equipment controller.
Implementing BACnet/IP based controllers takes careful thought and planning where BAS expertise provides value in avoiding pitfalls that can cause issues in the construction phase. Incorporating BAS expertise from a vendor, who specializes in controls, will ensure that the BACnet/IP based controllers being installed on-site will function optimally for years to come.