The Battery Backup Power Supply/Charger comes in 2 Voltages, 115V and 240V. Charger is connected inside the Battery Backup Unit (BBU). The charger has two charging rates depending on the battery voltage level. A 3-amp fuse is used to protect the ac-line monitor. Two testing jacks are provided on the front of the board for testing voltage. Charger has an Output Voltage Control or 'Pot' for adjusting the output voltage level.

The Battery Backup Unit (BBU) provides emergency dc power for Honeywell Total Distributed Control (TDC 3000) if:

1. AC line supply is at zero volts +/- 3 volts for more than 0.5 milliseconds.

2. AC line voltage zero crossings are more than 12 milliseconds apart.

3. DC system power decreases below 21.0 volts.

Switching to battery power is automatic when the above conditions occur. Return to normal operation is also automatic for the first two conditions. For the third, the manual reset button must be pressed. Provisions for a remote reset button is provided.

All BBU's supply 40 ampere dc output, but the correct model must be selected to accommodate the ac line power available.See Table below

An integral relay is supplied in all models that automatically connects the BBU to the bus bars when required.