How many field relays are typically needed for an elevator recall configuration?

In an elevator recall configuration, it is standard practice to use three field relays to ensure proper functionality and safety. The first relay typically controls the operation of the elevator's recall function to bring the elevator to the designated floor in the event of a fire. The second relay may be used to deactivate the elevator service during an emergency situation, preventing the elevator from responding to regular calls while the recall is activated. The third relay serves as a backup or for additional signaling to confirm that the recall has been successfully initiated and the elevator system is engaged in emergency operation.

This configuration ensures that proper protocols are met for fire safety standards in buildings, allowing for an efficient and safe response in emergencies. The use of three relays also provides redundancy, which is essential for maintaining system reliability.