Johnson Controls




This is the complete M-Tool Package for a new installation.

  • Includes HVAC Pro configuring and commissioning utilities for the UNT, AHU, VAV, and VMA Metasys N2 Open devices.

  • Includes GX-9100 configuring and commissioning utilities for the DX-9100

  • Includes many other utilities

Note: This software will not run on a 64-bit OS.
Note: Supports COM1 and COM2 only

All S4 partners are required to provide pre-sales engineering support and 1st level technical support to their dealers and integrators. For Schneider Electric dealers and branches the best way to request this support is to email the problem or assistance request details into the Product Support (PSS) queue directly:


Alternatively, there are different dial-in numbers people can use to log a new case (one for each of the three different cities where PSS is located).

Emailing this address (or calling in and dictating your case details to the person manning the phone) starts the process. PSS will facilitate any necessary escalation within the Schneider Electric support organizations or to The S4 Group.

If there has been a history of devices going off line in the pure Metasys environment it is a sign that something is wrong.

  • It could be bad wiring,

  • it could be too many N2 devices on the bus,

  • it could be EMF,

  • it could be a bad transmitter on a N2 device,

  • it could be multiple masters accidentally installed on the bus.

Determine the issue and correct it before proceeding with the integration.

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 ...

We've seen multiple areas where improvements can be made in existing N2 buses. From an electrical point of view the N2 bus follows the RS-485 standard with a N2+, N2-, and reference line. In many cases we will point you back to JCI documentation for details. We're not going to try to re-engineer the N2 bus technology. It is what it is.

We have seen many cases where either improper installations or just normal wear and tear over the years has taken its toll. It's also a fact that once you integrate to a legacy N2 bus with either the OPC-N2 Router or the BACnet-N2 Router it will be driven harder than it has ever been driven before. If anything is marginal, it will be exposed by the additional load put onto the system.

We always advise our integration partners to validate the N2 bus as part of determining the scope of an integration project. In fact, we advise them to specify in their contract that the customer deliver to them an in-spec and working N2 bus with wo...

The more information you have at hand the less risky a N2 integration will be and the more successful the project will be. In preparation for a N2 integration we always recommend that you:

  • Use HVAC Pro and create a Network Map report with it. This will tell you the hardware type, Firmware versions, and application loaded into each N2 device.

  • If you see any Generic IO / Point Multiplexor applications this is a red flag. That means that the logic driving those points is back in an NCM, or other supervisory controller. You can still do a very successful integration. You just need to do more planning.

  • Make sure that each N2 bus segment is within electrical specifications. You can use the ComBus Quick Tester or a DVM. You will be driving the N2 bus harder than it has ever been driven before so any weakness will come out.

  • Review as built drawings and any other documentation that is available for the Metasys installation. I've taken the approach of s...

When we designed the S4 Open Appliances we determined that we would stop short of providing these services. Johnson Controls has very effective tools for performing these functions that are aware of all of the variations in firmware, application revisions, etc. We didn't feel that we could add any value in this area.

Use HVAC Pro for N2 Open devices like the UNT, VAV, and AHU

Use HVAC Pro for the VMA

Use GX-9100 for the DX-9100

One of the things that we did include in the design is the ability to easily determine the application loaded into N2 devices, the firmware version running in the device, the original configuration file name, etc. This information is provided on the properties page for each device in the Building Control Network, BCN, folder. The information provided by each device type varies. Details for many N2 devices are provided now. Others will be added in the future as time and resources allow.

We developed the concept of Device Type Templates so that we would not have to rely on Metasys configuration files being either available, or up to date. They also expose more points than Metasys typically would. For instance PID loop tuning parameters and other parameters that would normally only be exposed by the Metasys configuration utilities are exposed so that 3rd party tuning and continuous commissioning applications can be utilized for a Metasys system.

As background, here’s the process that we use in the Configure wizard to try to find the best match with point mapping. N2 devices are interrogated to determine their hardware type and the application loaded into them.

1) Best case – we have a Device Type Template that matches both the hardware type and the application loaded into device. We refer to these as Application Specific Device Type Templates.

2) Next best – we match on the hardware type but not the application. We assign a generic point map ...

The VAV Modular Assembly, VMA, was one of the last device families to receive support in the S4 Open Appliances. These devices utilize their own variation of the N2 protocol referred to as N2B. With this work completed we support all variations of the N2 protocol and any N2 device that could be found on a N2 bus.

The OPC server associated with the S4 Open: OPC-N2 Router provides a Quality ;attribute for each point that it publishes. This indicates if the S4 Open Appliance is successfully talking to the field devices and retreiving data points. Unfortunately, some OPC clients ignore the Quality indicator and instead default the data values to zero.

The S4 Open Appliance will retry transactions to a N2 device multiple times before it gives up and returns a BAD Quality indication.

Another symptom of this same problem is that the Configure Wizard fails to find all of the N2 devices on the bus. If the Configure Wizard does not find a device that you know is on the N2 bus that tells us that there was interference during the time that we were trying to access N2 address XX (in hex). It is not necessarily a problem with the device at this address. The Wizard simply saw the bad transmission in the time frame that we were expecting a response from this device.

  1. Create the device in the physical network in which it resides (network n -> new -> field device)
  2. The "Define Physical Device" window will open; assign the N2 address for this device
  3. The device should now appear under the correct N2 network
  4. Now create a device object in the Building Control Network. Specify the N2 address that you want the device published to in the Upstream N2 network. (BCN -> New -> Device...)
  5. Link this object to the Physical Field Device you created in the physical network
  6. Assign the appropriate device type template for this device 
  7. The device is now integrated into the system and can be discovered by your BACnet client

The Metasys N2 bus follows the RS-485 standard for its physical and electrical characteristics. It runs at 9600 BD, half duplex using N2+, N2-, and Ref wires. Our S4 Open appliances are pre-configured to have all Com ports operate in RS-485 mode.

If you run any of the JCI Metasys configuration or commissioning tools HVAC Pro, GX-9100, etc. from your labtop or another Windows PC and want them to communicate the the N2 bus via their COM port you'll have to utilize either a USB to RS-485 or a RS-232 to RS-485 converter.

We have been using RS-485 converters from B&B Electronics www.bb-elec.com to connect our PCs to the N2 bus.

For RS-232 to RS-485 we use their model 485SD9TB

For USB to RS-485 (N2 bus) we use their model number 485USBTB-2W

The USB Serial Port technology has become so standardized that most manufacturers' products should work fine although the B&B products are the only ones we have tested. Note that you may have to a...

The JCI design of the N2 bus is fixed at 9600 Bd. We have to live with that. It can’t be changed.

So, the problem becomes how do we accommodate BACnet IP or OPC transactions coming in at Ethernet speeds?

  • Transparent Caching and BACnet COV support improve efficiency

  • Validating the N2 bus, repairing any installation problems, and removing sources of electrical interference improve performance

  • Breaking the N2 bus into smaller segments distributes the load. Each segment may come into a separate Downstream N2 Interface on a N2 Router or each one come into a separate N2 Router

  • Poll rates may need to be adjusted to frequencies more realistic for the capabilities of the N2 bus

As our integration partners have been digging into some of the older Metasys® installations they are finding Generic IO / Point Multiplexor applications much more frequently than I thought they would.

You can still do a very successful integration with these devices but it may take a bit more planning than if they were loaded with more traditional Metasys® applications.

  • You can process the .PRN Metasys configuration (resource) file for these devices through the S4 Configuration File Conversion Utility to create a custom device template

  • You may need to investigate custom logic in the Metasys supervisory controller. For the NCM this would be GPL or JC Basic logic.

  • You may be able to determine how the points are used by investigating the assignment and presentation of points in the Metasys Operator Workstation

  • You can investigate Single Side Loop logic, Interlocks, etc. programmed into the N2 device itself utilizing HVAC Pro

Most N2 devices do not contain a time of day clock that you can access directly. They do have an on-board clock that can be synchronized with the head end and is used as a fallback when the N2 device becomes disconncted from the head end. In normal operation they completely rely on a supervisory controller to tell them if they should be in Occupied or UnOccupied mode by toggling a binary point.

Typically, you’ll see set points for Occupied mode and another pair for UnOccupied mode. Simply have your new HMI or another (BACnet or OPC as appropriate) controller toggle the Occupied point in each N2 device to indicate the mode that you want each controller to operate in.

Check the manufacturer documentation for each N2 device and application supported by it for the correct point to toggle the Occupied / UnOccupied status of the device and the point names assigned for the setpoints.

One of the most important aspects of a successful Metasys integration is in taking the time to understand the existing N2 devices and their configurations.

  • HVAC Pro is the Metasys configuration and commissioning utility used for N2 Open devices like Unitary Controllers (UNT), AHU, and VAV controllers. It is also used for the VAV Modular Assembly (VMA) devices.

  • GX9100 is utilized to program and commission the DX-9100 device.

These utilities are available as part of the M-Tools package through authorized Metasys distributors. There are frequent discussions about acquiring, installing, and working with these utilities on the HVAC Talk forum, http://www.hvac-talk.com.

You can also purchase the M-Tools package through The S4 Group.

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Installation and Operation (PDF)

User Guide for the S4 Open Appliances

Configuration File Conversion Utility (PDF)

S4 utility that converts Metasys configuration (Resource) files to templates for the S4 Open Appliances


Technical Presentation (PowerPoint)

S4 Open Appliances Technical Presentation