Installers and security managers need to take into account that in most access control systems, electric strikes are the gatekeepers and they deserve more than passing attention. Buying low cost strikes and installing them in a slipshod fashion is like building a goal with single lever locks.

In a typical electric strike installation, there are two key components. The strike is fitted into the door jamb and has a bolt pocket that holds the latch securely. When the strike is opened, its pivoting lip, or keeper, rotates away from the pocket allowing the bolt to be pulled away. The latch is embedded in the door and has no moving parts or power demands. The strengths of electric locks include their ability to handle high traffic areas effectively (in really high traffic areas, magnetic locks can be better), and the fact that they cut down on manpower requirements. Strikes also allow timed opening, multi-functioning and interfacing with integral safety systems.

Strikes give positive door status and lock status indications, as well as allowing remote and automatic door control. They eliminate the costly suiting of mechanical locks and end the need for key cutting and copy controls. Using an overall access system with electric strikes allows administrators to reprogram locks remotely.

“Probably the fundamental question security managers and installers will face relates to whether or not the door is fire rated or simply an internal access point”

There are a number of things to consider when buying electric strikes. For a start, it’s important that solenoid bolts are continuous duty or CDR rated if they are fail safe. Of course, all fail-safe locks should be DC-powered. A CDR rating is necessary to ensure they don’t wear out prematurely due to being constantly energised against a spring.

Non-CDR rating would mean a large current draw and an unwelcome build up of heat that could slow the mechanism down. Installers and specifiers should also ensure any fail safe locks installed are intermittent duty rated (IDR). These locks need power to pull a bolt out of a lock or to open a strike plate. The periods of idleness these locks experience mean it’s vital that the right amount of magnetism is generated by the lock when needed. Too much current blows a fuse and too little causes the lock to open slowly or not at all.

Choosing a strike

One of the challenges faced when choosing an electronic locking device is the enormous range that’s available. Along with this, different types of lock are often generally suitable for a range of applications, making it hard to work out which option is going to be best. When you’re making your selections, think about the realities of your own site.

Something to consider early on is the preload of an electric strike – in specifications this force is often measured in Newtons, which are a value of force rather than weight or pressure. Essentially 1 Newton is the force required to accelerate a mass of 1kg at the rate of 1 metre per second, per second. If you find it easier to think of force in terms of weight measurements, a Newton is about 0.224809 pounds or 0.101972 kg of force.

This pre-load issue relates to the jamming of electrically operated doors caused by pre-loads that are higher than the strike is rated to handle – a quality fire-rated lock might have a pre-load rating of around 200N and the entire locking solution will need to match this.

In addition, serious emergency escape locks will offer side-load immune release mechanisms. You might want this capability if your locks are going into egress points likely to carry large numbers of people in the event of emergency evacuation. Also it goes without saying that all emergency doors – and if possible all egress doors – should open outwards. Doors installed this way guarantee that a crush of people on the inside of a locked door can never block an inward opening emergency exit. Supporting this sort of installation, side-load immune locking mechanisms guarantee that no matter how much pressure panicked people put on the inside of an electrically locked door, the locking mechanism will still release in the event of a fire alarm and/or a fail-safe event.

Probably the most fundamental question security managers and installers will face relates to whether or not the door is fire rated or simply an internal access point. Fire rated doors need a heavy duty strike that has a fire rating and is specifically designed for high use applications.

Adding to the security manager’s dilemma will be the different types of door jamb – variations have differing needs and you’ll want to assess these requirements before making a decision. The three most common jamb types are timber, aluminium and steel. You’ll most commonly run into timber and aluminium door jambs in front and internal doors, with steel jambs used for fire proof doors. Complexity is also going to be introduced by relevant building codes – some codes insist that in drywall installations (either metal or timber jambs), only internal solenoid locks are used and teamed up with lanky faceplates which ensure minimum gouging of the wall itself.

Typically, hollow steel or aluminium jambs will accommodate pretty much any electric strike of suitable size. Things do get complicated with aluminium-framed glass doors. The glass is usually encased in the 3-odd centimetre wide jamb, surface of the jamb making installing the strike particularly hard.

Essentially, it means the installer is required to put in a strike that’s compact enough to fit the jamb width without cutting the glass. Sadly, the most compact and most secure strikes are not the same thing and in most cases finding some sort of balance between architecture and protection will test security policy. The same rules that apply for drywall installs should also be used as guidelines for concrete filled metal jambs – concrete is often used as a stabilizer in fire doors. Installs like this need a low profile strike with an internal solenoid. Another thing to take into account is the existing lockset. No question, the lockset type will have a determining effect on the strike chosen. Installers are usually expected to match whatever lock the interior designer or architect has chosen with the needs of an electric strike, and seldom will the needs of the two mechanisms be met.

“In a good installation, the lock will be a press-fit. Never overcut to allow for imperfections in your work. Any movement in the lock may impact on the tolerances of the lock and lower its security levels”

At the very least though, security managers should make sure installation teams get the benefit of working with an ANSI lock style that is catered for by strike manufacturers. Trying to wring some sort of security from architectural locks chosen on the basis of aesthetics will always compromise security. You’ll obtain a seal but only if no force is applied to the locked door.

The problem works in reverse, too. In the interests of coming up with the most competitive quote, a non-grade electric strike will be installed to keep a Grade 1 heavy duty lockset. These two will not be good friends. The problem is that the lockset is burdening the strike – especially if there’s any traffic using the egress point.

Any combination of heavy duty mortise lock incorporating a steel 3-piece anti friction latch and an auxiliary dead latch feature, with a light duty electric strike complete with a narrow style zinc cast faceplate, a zinc cast latch keeper and shallow cavity depth or height that’s designed for light application,s simply builds in malfunction.

All you installers forced to team up this sort of combination on glass doors that lack the room for a properly matched and graded electric strike should argue a case for electromagnetic locking solutions – at least on internal doors.

Handling installations

Before you set out to the site before access control installation, set up the locks properly at the work bench. First check to make sure the DC diode that crosses the positive and negative wires is already in place. If it’s not, the diode will be included in the packaging. Locate it and tape it to the lock. Next, check if the lock will fail safe or fail secure in the event of power failure.

If the lock needs to be set up manually, remove its cover and access the lock’s relay. The brass locking pins can be removed and their insertion pattern changed to fail safe. Decisions about fail safe and fail secure will be influenced by a site’s application and the customer’s requirements.

Good electric strikes are supplied with a template to assist with installation. Once at the site, place the template on the door then mark it out so you can make the necessary cuttings. Cut out both top and bottom marks on the jamb, as well as the markings on the opening edge of the door and once your initial cutting is completed, use the lock as a template.

In a good installation, the lock will be a press-fit. Never overcut to allow for imperfections in your work. Any movement in the lock may impact on the tolerances of the lock and lower its security levels.

The next step is to put in the cable. The method you’ll use will be dictated by the construction of door frames and walls. You’ll either come down through the wall and then through the frame (timber frame, timber door, gyprock wall) or you’ll conduit down the wall and come in through the frame from the side (concrete-filled, steel frame, steel door, cement wall).

Never use external conduit runs on the unsecured side of the door and try not to use them on the inside either. If you have to install cable this way, be sure to use steel conduit and if there’s camera support for the door, include the external cable run in the camera’s field of view if possible.

Major challenges will be fire doors. They have a fire-rated steel frame filled with cement to absorb heat and to resist buckling. Once your template is cut, use a cold chisel or similar tool to carve out a cable channel in the cement and then drill a hole through the jamb or the wall to carry cable from the lock to the controller.

Once the holes are drilled for wiring, take the cable back to an input on the door controller located in the closest electrical riser or wiring closet. Ensure your wiring is neat, firmly secured and tagged so it’s easy to identify. The cable will have a pair of power wires and additional wires reporting lock status including open, closed or alarm.

With the wiring in, you can look at the installation of the lock itself. Drill the top and bottom holes then tap them to suit the screws supplied. To give yourself a third hand, turn the lock back to front and screw it to its top positioning hole as you connect the exposed wiring. This practice will ensure you don’t use too much wire and it will get the lock closer to your face for the careful work needed.

Now twist the positive and negative wires together, placing the DC diode in position across them. The anode of the diode will go to the positive and the cathode to the negative wires respectively. You then solder the diode into place using the minimum amount of solder for a firm joint.

Once the solder has set, fold the joint down so it can be heat shrunk. If it’s not your practise to heat shrink soldered joints, it should be. Covering connections reduces the possibility of short circuits and costly maintenance call-outs.

Before you turn the lock back around by removing the third hand screw, make sure you label wires and once this is done, put the lock into the door, making sure wires don’t squeeze out the sides. Screw the lock into position, making sure the pivot lip is correctly aligned with the latch.

As you go through your commissioning procedure, check that door handles are correctly orientated and egress is possible from the secure side of the door by not the unsecured side. Now go to the reader and test the lock’s function using the appropriate credential or switch. The controller will power up the lock and the pivot lip will rotate, releasing the strike.