849A-ZOD24

The Allen-Bradley 849A-ZOD24 Pneumatic Timing Relay is a robust and simple-to-install timing solution for the kinds of industrial applications that take place in hazardous worksites and environments, especially in potentially explosive environments where other types of timing relays would increase the risk of fires or explosions. The time delay function in this pneumatic timer is achieved by the use of an open pneumatic damping system that involves the activation of the relay contacts for a user-defined amount of time. The Allen-Bradley 849A-ZOD24 Pneumatic Timing Relay’s operating principle is that the electrical signal reaches the coil, it magnetically attracts a metal shaft and activates a needle valve that releases the air that was contained inside the pneumatic bellows with external pressure in order to dampen the activation of the integrated relay switch. The nominal voltage rating of the switch’s electrical contacts should be 120 Volts AC at 60 Hertz or 110 Volts AC at 50 Hertz.

The Allen-Bradley 849 series 849A-ZOD24 Pneumatic Timing Relay is an on-delay type of timer, meaning that the electrical contacts in the device do not change status immediately after the coil receives an activation signal, but that they wait until the pneumatic bellows displaces all of its air before closing the circuits. As the bellows empties, the electrical contacts of the Allen-Bradley 849A-ZOD24 Pneumatic Timing Relay get closer to each other until they reach the point where their status changes from open to closed, and they start conducting an electrical current. Only qualified and trained technicians should perform maintenance and/or repairs in this timing unit. The electrical contact block for this timing relay may be replaced when it is damaged, and additional or auxiliary contacts can be added if more circuits are needed in the final user’s applications.