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 may 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. Our S4 Open appliances will work with any device that is compliant with the N2 protocol specification.  Many competing integrations only implement the N2 Open protocol.

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 controled the distribution of the documentation. They did not publsh 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.