The NBC over pressure gauge shows the pressure differential between the air inside the shelter and outside air. The air pressure is regulated to a maximum of 25 mbar by a pressure relief valve mounted in an inner wall of the shelter.

The Power on indicator lamp (Red)
indicates that a power supply to the NBC unit is available.
The Unit running lmap (Green) indicates that the NBC fan motor is running.

The NBC unit control switch is a simple toggle switch. Putting this switch into the on position will operate the NBC fan and operate the NBC/ACU fresh air interlock.

The ACU/NBC fresh air interlock is provided to ensure the ACU fresh air inlet valve is instantaneously closed when the NBC filter unit is switched on.

The NBC system has been designed to have a very simple control sequence. When NBC filtration and protection is required the operation of a toggle switch on the NBC control unit will provide a power supply to the NBC fan via the access panel micro switch. This activates the fan motor, drawing air through the NBC filter unit and out into the shelter. The operation of the toggle switch also operates a relay within the NBC control unit; this relay breaks the ACU/NBC fresh air interlock causing the ACU fresh air valve to close.