Metasys N2: Gateways, Loggers, Tools

What is Metasys N2?
Metasys N2 is a Johnson Controls protocol used to integrate building automation controllers under a Metasys BMS.

Can Metasys N2 integrate with BACnet or Modbus?
Yes. Our gateways translate N2 points into BACnet/IP, BACnet MS/TP, or Modbus TCP/RTU for modern systems.

Is Metasys N2 still supported?
While N2 is legacy, many buildings continue to operate N2 controllers. Gateways allow continued use and phased migration.

What hardware is used for Matasys N2 integrations?
Deployments use the FieldServer QuickServer® platform to ensure reliability, security, and consistent setup.

What physical layer does Metasys N2 use?
A communication data protocol consisting of the following layers of information: Devices, properties, objects, services, BACnet Interoperability Building Blocks (BIBBs). Bacnet protocol can be transported through several types of network: PTP, MSTP, ARCnet, Ethernet, I/P.

How is a BACnet Router different from a BACnet Gateway?
BACnet routers connect two different types of networks, for example, BACnet on Metasys N2 Bus to BACnet on IP. BACnet Gateways connect two networks of the same type, for example, two BACnet Metasys N2 Buses into a single virtual bus.

What is FieldServer?
A protocol Gateway to integrate two devices that speak different protocols. It takes the messages from one protocol and converts them to another.

What is JCI?
A non-proprietary (open) master-slave communication architecture created by JCI for building automation.

What are PICS?
Protocol Implementation Conformance Statement. These are documents produced by vendors which specify the properties, objects, services, and BIBBs of a device.

Is N2 a Standard?

The N2 protocol was defined by Johnson Controls for the Metasys system. It was based on the OPTO-22 optimux protocol but over its life was extended many times.

The N2 Open protocol definition was published by JCI for 3rd parties to be able to natively support the N2 Open protocol in their devices. The JCI UNT, AHU, and VAV controllers support this same protocol.

N2 was extended with the System-91 protocol to support System-91 devices like the DX-9100.

N2 was again extended with the N2B variant to support VMA devices.

All of the variations of the N2 protocol will co-exist on the same wire and all generations of Metasys supervisory controllers can talk to all N2 devices. 

Is N2 a standard? JCI did a very good job at marketing their Metasys Compatibility program and publicizing the fact that many devices could be integrated into Metasys. They did make portions of the N2 Open protocol available but very carefully controlled the distribution of the documentation. They did not publish the specifications to allow Metasys to be integrated into other systems. They did not openly publish the System-91 or N2B variations. I would consider the N2 Open portion of the protocol a proprietary standard.