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How does redundant group control work in a Network Air FM unit.

Published date: 03 September 2020


How does redundant group control work in a Network Air FM unit. 

Product line:
ACFM, IR40, Network Air FM. 

All Serial Numbers. 

Install, Repair. 


Nome Redundant Group Control


• Primary System – system designated to actively control the environment. • Backup System – system designated to remain idle and only provide environmental control

upon request • Failover – process by which a Backup system takes over for a failed system.


Features of RGC

• Redundancy – When a system fails, a Backup system will automatically take over its duties.

• Runtime Balancing – When enabled, Primary systems and Backup systems will periodically swap roles.


Features, cont.

• Load Sharing – When enabled, Primary systems can request assistance from Backup systems in controlling the environment on a per-function basis.

• Demand Fighting – When enabled, reheat will be inhibited on all systems in the group when cooling is active on any system in the group.


Features, cont.

• Setpoint Sharing – When enabled, cooling and reheating setpoints and deadbands will be shared among all systems in the group. Humidification and dehumidification setpoints are

always shared among all systems in a group.



• All group settings (except System Failure Events) are automatically copied among all systems in the group.

• No group setting can be changed (except Number of Systems in Group) if a communications lost alarm is active for a system in the group. This behavior applies to setpoints and

deadband if Setpoint Sharing is enabled.


Group Configuration

• Number of Systems in Group – It is important to set this accurately, and before setting up other parameters. When this is set to “1”, all group functionality is disabled.

• System Roles/Redundancy – When Runtime Balancing is disabled, system roles are assigned manually. When Runtime Balancing is enabled, system roles are determined automatically.

The user specifies the number of Primary systems. For N+1 redundancy, this should be set to one less than the total number of systems in the group.


Group Configuration, Cont.

• Group Name – provides a 29 character description of the group. It is provided primarily for use by the NMC and BMS user interfaces.

• Idle Blower Speed – Determines the operation of blowers on Idle Backup systems. Set this to “Normal” for fastest system failure recovery.


Group Configuration, Cont.

• Group Fire Alarm

• Group Smoke Alarm – These provide the capability for the entire group to shutdown when fire or smoke as applicable is detected by any module on any system in the group.


Group Configuration, Cont.

• Communications Loss Failover – When enabled, the loss of communications with a system will be treated as a failure of that system. This is enabled by default, and in general should

remain enabled. However, there may some situations, such as limited coolant pump capacity, in which it may be desirable to set this to disabled. The user should be aware

however that powering off a system is treated as a Communications Lost event and if this is disabled, no Backup system will take over for the lost system.


Group Configuration, Cont.

• Load Sharing (LS)– There are two aspects to LS configuration. The first part controls whether LS is enabled for a particular system function or not. The second part controls the

threshold at which assistance is requested.  


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