I received a work order that an ex- terior door restricted to card swipe ac- cess was not releasing when an autho- rized card was used. The door had a Von Duprin 99 series rim exit device used in conjunction with an older Von Duprin 6100 series electric strike (Figure 1). Aſter trouble- shooting, I removed the mounting screws, disconnected the strike, and determined that the electric strike, set for fail secure, was receiving proper voltage/amperage (Figure 2) when an authorized card was used, but the electric strike would still not release. At this point, I want to stress that assuming is never a good idea. Always verify the correct voltage with a meter and check that the power sup- ply can provide the rated current or amper- age required by the strike. Also verify that the wire size and length is adequate to prevent too great a voltage drop. Visual inspection showed no damage to the external components of the electric strike or foreign objects within it preventing normal operation. Sometimes, especially on college campuses, individuals come up with make- shiſt ways to keep doors open and/or unlocked, and the items used can inadvertently cause otherwise fine door hardware to not work by jamming key components. An electric strike, believe it or not, is a very, very simple device. The only moving part in this strike aside from the keeper’s spring, and nearly all others, is the solenoid. That had to be culprit. I then reconnected the electric strike to its power source and swiped a working card a few more times. Each time I held my finger to the solenoid — which is placed on the out- side of the electric strike on this particular model — I felt nothing. You should feel and hear movement when a working solenoid is energized, but more on that in a moment. Case closed: we had a solenoid that had failed, and it needed to be replaced. But could it? Some manufacturers offer replacement kits for their electric strike’s solenoids; some don’t. In this case, Von Duprin offered such a kit. Von Duprin’s 6100 series are beasts of electric strikes; they’re rugged, of solid construction, and — by extension — expensive. Kudos to Von Duprin for selling replacement sole- noid kits on an otherwise indestructible electric strike. I’d much rather pay for a solenoid replacement kit than a brand new 6100. How Solenoids Work with Electric Strikes Solenoids have been ex- plained in this magazine before, undoubtedly bet- ter, and most of you prob- ably already know what they are and how they work. But for those who don’t, solenoids are essen- tially electromagnets. The main housing (Figure 3) of the solenoid contains coiled wire and works in conjunction with an armature. Armatures, sometimes referred to as plungers or slugs, are cylinder-shaped and con- tain ferrous metal, which is magnetic. Like all elec- tromagnets, when cur- rent is applied, the coiled wire generates a magnet- ic field. This causes the armature to move up or down, depending on the design or intended usage of the solenoid. For example, the Von Duprin 6100 series electric strike I am fixing is fail secure. When not energized, the armature rests in position that prohibits the electric strike’s keeper from moving. When the sole- noid is energized, the armature is attracted to and therefore liſted by the magnetic field Figure 2. The electric strike was receiving the proper voltage. Figure 3. The main housing of the solenoid works in conjunction with an armature. produced by the coil, and the keeper is then able to move momentarily. The Fix Luckily for me, I had a 6000 series solenoid replacement kit on hand (24VDC - part no. 050240). The kit, also available in 12VDC FEBRUARY 2015 KEYNOTES 33
