Are Metasys Generic IO / Point Multiplexor applications Supported?

Yes. However, it takes more work than for the application specific controller applications. Consider the existence of Point Multiplexor applications a Yellow flag when preparing for an integration. It says that there is probably a lot of logic in the NCM driving the points in these devices.

The normal designed operation of the Metasys N2 DDC controllers is that if they lose communication with their supervisory controller (NCM, Facilitator, Companion, N30, NAE, Facility Explorer) they will continue operating the building utilizing the last available values or default values for all parameters, etc. For instance, Outside Air Temperature is typically a global variable that is distributed by the supervisory controller to all N2 devices that need the information. If the supervisory controlle fails, or communications to it via the N2 bus are lost, the individual controllers will continue operating with the best information they that have available.

If N2 devices are loaded with Generic IO / Point Multiplexor applications the whole ball game changes. This turns the intelligent UNT, or AHU controller into a dumb IO device. All associated logic is handled by the supervisory controller. Every decision that is being made is done in the supervisory controller. That is why when you disconnect the supervisory controller the entire building stops operating. Even before the integration process started the building owner was at extremely high risk if any of their supervisory controllers or N2 buses were to fail. There is no failsafe. The building just stops working.

I see 3 options for resolving this situation.

1) Keep the existing N2 controllers in place with the Generic IO / Point Multiplexor application loaded. Reverse engineer the logic in the supervisory controller. Then, replace the logic in BACnet or OPC controllers that you provide. You’ll have a considerable amount of test time to tune your new logic and make sure that it controls the building the way you want it to.

2) Keep the existing N2 controllers in place but reprogram them with the appropriate Metasys application using HVAC Pro. You then will need to re-commission the controller. This will take Metasys expertise to make it happen successfully but it is probably the least expensive, and least risky, approach.

3) Replace the N2 controllers with BACnet controllers appropriate for the task at hand. Obviously, you’ll have the hardware cost, the commissioning cost, and the cost of either getting another bus to those controllers or segmenting the N2 bus and reusing that cable.

The worst option is to do nothing. The building owner was at risk from day one of this installation. As the Metasys supervisory controllers, and the N2 bus itself,  age they are more linely to fail. The risk only increases every day that nothing is done.