What must be considered when installing magnetic contacts on a steel door?

What must be considered when installing magnetic contacts on a steel door?

• A. Steel alters the magnet characteristics of the contacts
• B. Steel doors cannot use magnetic contacts
• C. Magnetic contacts require no clearance
• D. Steel enhances magnet strength

Answer: (A)

Steel changes the magnetic circuit. When a magnet and reed switch are mounted on a steel door, the ferromagnetic door becomes part of the flux path, altering reluctance and pulling or distorting the magnetic field seen by the switch. That means the same magnet and clearance that work on nonferrous doors may not produce reliable operation on a steel door. To maintain proper sensing, you must account for this by choosing an appropriate magnet strength, adjusting the air gap, and/or repositioning the components (and testing to confirm reliable operation). The bottom line is that steel alters the magnet characteristics, so the installation must be adjusted accordingly.

Steel changes the magnetic circuit. When a magnet and reed switch are mounted on a steel door, the ferromagnetic door becomes part of the flux path, altering reluctance and pulling or distorting the magnetic field seen by the switch. That means the same magnet and clearance that work on nonferrous doors may not produce reliable operation on a steel door. To maintain proper sensing, you must account for this by choosing an appropriate magnet strength, adjusting the air gap, and/or repositioning the components (and testing to confirm reliable operation). The bottom line is that steel alters the magnet characteristics, so the installation must be adjusted accordingly.