Integrating Design

Oct. 27, 2008
Glass Door Locks

Q: We have to install a shear lock on a Herculite door with a rail at the top. The door does not have a stop (it swings both ways so to speak). After researching the available shear locks, I am wondering: since it is a Herculite door, what sense does it make to install a 2700 lb. lock when the door will probably shatter under considerably less pressure?

A: We all know that a glass door is not the epitome of security. However, they are aesthetically pleasing and a rather common architectural feature. Electrical locks are frequently used on this type of door because: it is desirable to control access; you can use a clock to automatically lock and unlock a premises; or the standard locking cylinder, which is typically located in the bottom rail is difficult for many individuals to reach. Users can also feel they are being put into a compromised position while bending over to lock or unlock the device.

Indeed, since your door is bi-swing and you have a channel at the top, you probably will want to use a concealed shear lock with the armature mounted in the top of the door and the magnet in the header/door frame. Selecting a shear lock whose physical size will allow installing it is the first criteria.

I would recommend selecting the highest power/best designed shear lock you can budget into the job, because it will pay you back time after time.

Bear in mind that the rated holding forces published by some manufacturers may be somewhat off base. The specs assume that full voltage is being applied to the shear lock and all other conditions which might adversely affect the bond are ideal.
One condition which can adversely affect locking and bonding is the distance between the armature and the electromagnetic portion of the shear lock. Herculite doors are famous for dropping and shifting as the pivots, the door closer and the building in which the door is installed begin to wear, weaken and shift. These parameters will challenge the shear lock to be able to properly align and pull up the armature.

For example, one shear lock on the market advises that it be installed so that the armature and electromagnet actually make contact when the door swings past it to be sure the gap between the armature and the electromagnet are minimal. Therefore, in doing this, the shear lock has the best chance of locking. Need I elaborate? If so, let me know.

A variety of manufacturers’ shear locks offer mounting kits which make adjustments to the armature height quick and easy. They offer holding and pulling power to assure your system will operate with minimal hassles.

As is often the case, if you start off with a shear lock that is marginal in the first place, you are guaranteed to be returning to the job repeatedly to tweak the shear lock in order to maintain satisfactory operation.