In Parallel-UPS configurations, the combined outputs of several UPS devices support the load. With this setup, PowerChute monitors the load as it changes to determine whether the mode of operation is Parallel Capacity or Parallel Redundant.

For example, you are operating in a Parallel Redundant mode (i.e., there are more UPS devices available than are required to provide power to the load) and then you increase the load by adding new servers. PowerChute detects if the mode of operation changes to Parallel Capacity (i.e., all UPS devices in the configuration are now required to provide power to the load). This could cause PowerChute to initiate a shutdown if just one critical event is triggered.

Scenario 1: Three 10kVA UPS devices supporting a 16kVA Server Load (Parallel Redundant)

In this Parallel Redundant configuration, two or more critical events occurring cause PowerChute to trigger a graceful shutdown of the server(s).

PowerChute follows these shutdown rules.

• 2 identical critical events (such as Low-Battery Condition: Occurred OR UPS turn off has been initiated) occurring in succession on 2 UPS devices cause a shutdown. The shutdown is immediate and no configured delay is counted down.
• 2 identical user-configured critical events such as UPS: On Battery occurring in succession on 2 UPS devices will cause a shutdown. Any configured delay is counted down first.
• 2 different critical events (such as Low-Battery Condition: Occurred and PowerChute cannot communicate with the Management Card ) occurring in succession on 2 UPS devices cause the event called Multiple Critical Events occurred which always leads to a shutdown. Prior to the PowerChute shutdown process starting, a 10-second delay is counted. No configured delay time is counted down.

Scenario 2: Three 10kVA UPS devices supporting a 23kVA Server Load (Parallel Capacity)

In this Parallel Capacity configuration, one critical event triggers a graceful shutdown of the server(s).

However, if 2 occur, they have these delays.

• If 2 identical critical events occur in a parallel capacity configuration, then the event is only reported once and any configured delay is counted down.
• If 2 different critical events occur, then both events are reported separately and the shortest shutdown delay of the two is counted down.

Scenario 3: Two 10kVA UPS devices supporting an 8kVA Server Load (Parallel Capacity)

In this Parallel Capacity configuration, one critical event occurs and graceful shutdown of the server(s) is not triggered as the single UPS device can still support the connected load.

Scenario 4: Two 10kVA UPS devices supporting an 8kVA Server Load (Parallel Capacity)

In this Parallel Capacity configuration, two identical critical events occurring causes PowerChute to trigger a graceful shutdown of the server(s). The shutdown is immediate and no configured delay is counted down.