How to set up group communications for an Network Air FM unit

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Issue:
This article contains the step by step instructions on how to set up group communications in a Network Air FM unit.

Product line:
Network Air FM.

Environment:
All Product models, all serial numbers.

Cause:
The purpose of this document is to provide a clear communication on how to properly configure a group of FM units to work together. Please review Application Note #82 if more clarification is needed.

Resolution:
Redundant Group Control or RGC is a collection of two, three or four systems that provide redundant functionality, runtime balancing, prevention of demand fighting, load sharing, setpoint sharing and backflow prevention. In order to better understand RGC, we need to define the different components of the group:

A Module is an independent, Computer Room Air Conditioner. A System is a set of one to three Modules operating based on the average temperature and humidity of all the modules in that system. The modules in a system work together as a single unit and up to three modules can be used in a system to increase the system’s cooling capacity. A Group is a set of two, three or four Systems that work together to provide redundancy.

In a system one of the modules is designated by the user as the “Main Module” and the rest of modules in the systems are identified as “Expansion Modules”. The main module is the controller for all the modules in the system and it contains the PCIOM boards, the Network Management Card and establishes communications with the BMS.

To enable the modules to work in a system or group, the only requirement is to connect them together with a CAT 5 cable terminated with RJ-45 connectors and to setup the dip switches on the controller board of each module to assign the main module, the expansion modules and the System number. For more information on the dip switches set up, see the Installation Manual.
The systems belonging to a particular group should be located in close proximity in order for the backup systems to service the load properly to that area.

In a Group, the Primary Systems are the systems designated to actively control the environment and the Backup Systems are designated to remain idle and only provide environmental control upon request.

When a Primary system fails, a Backup system will automatically take over its duties; this process is called Failover. The user must select from a set of System Failures the events that will cause a primary system to failover. This selection must be configured for each system in the group and System Failures for one system do not necessarily have to be the same ones for other systems in the group.

1) Please locate the control board of the FM unit [Figure 1] and land the Cat5e cables according to Figure 2. The in port is J21 and the out cable goes to J22 which connects the next unit in the group [Figure 3].

1 Figure

Figure 2

2. Please select one of these configurations for the dipswitches on the FM control board located in the small electrical box on the right hand side of the FM

NOTE: Please remove power from the Module at the mains input breaker

.

3.After adjusting the dipswitches cycle power on for the FM and proceed to the Group configuration menu [Setup > Group > Group Config].
a. # Systems - Adjust the # of Systems to reflect the actual number of FM units in the system.
b. Setpoint Share – Enable or disable setpoint sharing among the Systems of this Group. When setpoint sharing is enabled, changes to the cool or reheat setpoint on any System in the Group are copied to all of the other Systems.
c. Idle Blwr Spd. Set the behavior of the blowers for Systems that are in the idle, backup, or failed states.
d. Grp Fire Alrm. Share fire alarms among the Systems in this Group. If the Group Fire Alarm setting is On, then all Systems in the Group will shut down if a fire alarm occurs in one System. If the Group Fire Alarm setting is Off, the alarms are still shared, but will not shut down other systems.
e. Grp Smoke Alrm. Share smoke alarms among the Systems in this Group. If the Group Smoke Alarm setting is On, all Systems in the Group will shut down if a smoke alarm occurs in one System.
f. Comm Loss Failover. Decide if the Group considers a System in the Comm Lost state to be failed.
i. • Off — The Group will assume that the System is still operating normally.
ii. • On — A backup System will be moved to the online state.

4.Please set the group configuration cooling load-sharing and System role-assignment functions
{Setup > Group > Group Settings}
g. Load Share. Enable or disable load-sharing requests for each mode. If load-sharing is disabled,
Systems cannot send requests for assistance to the Group.
h. Load Share Thrshlds. Set the load-sharing thresholds for each mode. If the environmental temperature or humidity is outside the range determined by the setpoint and threshold, the System will generate a load-sharing request. NOTE: APC recommends 4F on the Cool/Reheat and 10% on the Dehumidification/Humidification (which are defaults). However, acceptable ranges for each mode are:

5) Please set the Sys Role Assignment. The System Role Assignment settings depend on the Run-time Bal setting.
• NOTE: If Run-time Bal is set to On, each System is rotated between a primary and backup role in order to spread the run hours among all of the Systems in the Group. Rotation occurs after 72 hours of operation. (Not modifiable)
– # Primary: Set the number of Systems to be designated as primary. The remaining Systems in the Group will assume the backup role.

• NOTE: If Run-time Bal is set to Off, you must designate the role of each System in the Group. The
System will retain this role until you change the setting.