9. Electrified Locks — Overview
Chapter objectives
1. Discover Why We Use Electrified Locks
2. Learn All about the Different Types of Electrified Locks
3. Understand How Electrified Locks Work
4. Uncover Insights into Lock Power Supplies
5. Understand Electrified Lock Wiring Considerations
6. Learn How Ohm's Law Makes Lock Circuits Work — or Not
7. Understand How Wire Gauge Controls Lock Circuits
8. Learn about the Different Types of Electrified Lock Controls
9. Get to Know Types of Locks That Are Not Recommended
10. Answer Questions about Electrified Locks
CHAPTER OVERVIEW
The selection of the correct electrified locks is critical to the success of every project. Where improper locks are used, the project suffers from any of the following problems:
• Failure to comply with code
• Requirement by Code Officials to remove locks and reinstall proper locks
• Improper function, causing traffic queues
• Unsafe exiting conditions
• Unreliable lock operation resulting in frequent maintenance
• Persons trapped within a space during an emergency
This chapter explains all about electrified locks and sets the stage for you to be able to select locks that will be code compliant, reliable, and easy to use. It will also cover information about how to select the right lock power supply and electrified lock controls as well as help you to understand how choosing the correct wiring for an electrified lock can make the difference between a reliable lock and an unreliable one that is in constant need of repair. Additionally, this chapter covers the basic rules for selecting the right lock and which ones to avoid.
The selection of the correct electrified locks is critical to the success of every project. Where improper locks are used, the project suffers from any of the following problems:
• Failure to comply with code
• Requirement by Code Officials to remove locks and re-install proper locks
• Improper function, causing traffic queues
• Unsafe exiting conditions
• Unreliable lock operation resulting in frequent maintenance
• Persons trapped within a space during an emergency
This chapter explains all about electrified locks and sets the stage for you to be able to select locks that will be code compliant, reliable, and easy to use. It will also cover information about how to select the right lock power supply and electrified lock controls as well as to help understand how choosing the correct wiring for an electrified lock can make the difference between a reliable lock and an unreliable one that is in constant need of repairs.
Keywords: Code, Electrified Locks, Emergency, Exit, Function, Operation
Author Information:
Thomas L. Norman, CPP, PSP, CSC, Executive Vice President, Protection Partners International
Why Electric Locks?
From the early days walls provided physical barriers, doors allowed passage through those barriers, and locks ensured that unauthorized people did not use those doors to pass into the protected zone. This all worked fine as long as only a limited number of people needed to pass through the locked door. But as a larger number of people were authorized to pass through, it was necessary to provide someone at the door to unlock the door, or else give everyone authorized a key to the door. As late as the 1980s, it was a combination of these methods that secured most doors in the world, but both approaches were problematic.
Guards at doors are expensive in any economy. At this time, a simple door guard costs about $9–12.00 per hour to the client. Assuming 40 hours per week and 52 weeks per year, the cost is about $16,640–24,960 per year just to guard one door. That had better be a pretty important door!
Distributing keys to all authorized users for a highly used door is also a problem. Employee turnover makes re-keying costly. The original cost of a key is about $1.00 each. If 5,000 people need to use a door each day the cost of the original key distribution is $5,000 plus the cost of actually distributing the keys. If the time to distribute each key is only five minutes, that will take 416 hours (52 days) to distribute 5,000 keys. At a simple cost of $8.00 per hour for labor plus 12 keys distributed per hour, the cost per hour rises to $20 per hour. Multiply that by 416 hours and the total cost to distribute the keys is $8,320.
Oh, and that is assuming that nobody gets fired or leaves employment. On average, a business employing 5,000 people with a turnover of only 15% per year (an exceptionally low employee turnover) will lose 750 people per year and hire 750 people per year. That is another 750 keys to be distributed (another 62 hours and $1,250 in employee and key costs). So the first year cost for keys for that door is $9,570.
And there are two other problems. This is not the only door to which employees may need a key in the facility. Remember, keys must be distributed to only the employees who need them and no others, and different doors need keys distributed to different people. So if the average employee needs keys to perhaps 12 doors, now the first year cost of keys is $114,840. It adds up quickly, don't you agree?
And we have not even talked yet about the cost of lost keys. It is hard to calculate how many keys might be lost in a year among a population of 5,000, but every key that is lost requires not only the issuance of another key to that person, but also a new key to all 5,000 employees. This is because that lost key is a key to a door that protects assets that the company is already willing to pay $114,840 to protect, so they are not going to let a key be lost somewhere out there, probably on a key ring with a key-tag given free at last year's 4th of July barbeque with the company's name or logo on it. And yes, that does happen. Companies are that stupid (search Google™ images for “key-tag Company Logo”). The company cannot just replace the key to the lost employee, they have to replace all 5,000 keys just to be sure that the guy out there who picks up the key ring with the company's name on it does not just decide to try out the “found” keys some day (and yes, that also happens). There have been cases where employees have reported keys lost just to cause the company the havoc of having to re-issue keys to all employees. For the record, I do not advocate anyone doing anything that is in any way illegal (unless it is hilarious).
So just for fun, let's assume that of the 5,000 employees, a mere 5% are too incompetent or stupid to keep track of their keys (and I am probably being gracious about the number of stupid people here). That is another 250 keys per year or virtually once each and every work day. So essentially the company has to give out another 5,000 keys every day they are open just to keep up with the number of lost keys. This would cost $8,320 (cost to distribute 5,000 keys) times 250 (keys lost per year), or $2,080,000 a year. And that is just for one door. Security Management is complicated isn't it? It kind of makes the guard look cheap at only $24,960 per door per year, doesn't it?
Of all the dumb ideas spawned in the 1960s and 1970s (and there were a lot of them), the idea of companies issuing keys to large numbers of employees was at the top of the list. It was not long until the gigantic line item in the security budget for keys was overwhelming the entire budget for executive martinis and golf. This got the attention of accounting departments who thought to themselves: “I think this is a bad idea. This is costing me martinis.” There had to be a better way to secure the facility.
Then they heard about Electronic Access Control Systems — enter the 1970s and Electronic Access Control Systems. It is pretty clear to see how an early access control system operating from a file-cabinet-sized computer serving less than 16 doors at a cost of a hundred thousand dollars or so (1970s costs) is a tremendous bargain compared to the cost of issuing and maintaining keys for a large population of employees.
So, while electrified locks were primarily used in prisons, jails, and in very limited commercial use to control access to a single or double door, access control systems presented a ready market for electrified locks. As the access control market grew, so did the need for electrified locks. Soon there were numerous types of electrified locks with each having its own purpose (or not). The industry developed some really loony ideas about electrifying locks for a while until Fire Code Officials put a stop to it.
Types of Electrified Locks
I have seen some pretty basic descriptions of the types of electrified locks over the years. But if you want to be able to sort through lock types and find the correct lock for a given application, it is essential that you understand all the ways that locks can be categorized. Here is the complete list.
All Electrified Locks fall into only a few common type categories:
• Electrified Mortise Locks
• Electrified Panic Hardware
• Magnetic Locks
• Electric Strikes
• Electrified Cylinder Locks
• Electromechanical Dead Bolts
• Combinations of the above
These can be further categorized into those locks that provide “free mechanical egress” (just push the bar or turn the handle and go), and those that require some other method to exit:
• Free Mechanical Egress Locks
• Electrified Mortise Locks
• Electrified Panic Hardware
• Electric Strikes
• Electrified Cylinder Locks
• Other Means of Egress
• Magnetic Locks
• Electromechanical Dead-Bolts
• Combinations of the above may fall into either category
Electrified locks can be further categorized into two other groups:
• Locks that use mechanical devices to achieve the lock/unlock function
• Locks that use purely electromagnetic means to do so
Other categories:
• Those that can be used with existing door locks and those that must be used alone
• Locks that are visually aesthetic and those that are not
• Locks that sit on the frame and locks that sit in the door
• Locks that work well in emergencies and locks that might be slower to use
• High-security, medium-security, and low-security locks
• Locks that make noise when they operate and those that are nearly silent
• Locks that indicate their lock/unlock status and those that do not
• Fail-Safe Locks and Fail-Secure Locks
As we progress through this book, you will see how understanding all of these different categories of locks will help you make the correct decision on which lock to select for a specific function.
How Electrified Locks Work
Electrified locks are mechanical or electrical devices that hold a door closed. All electrified locks use electromagnetism to achieve this function. Electrified locks fit into two broad categories:
• Locks that use electromagnetism to activate a mechanical lock mechanism (electromechanical locks)
• Locks that use electromagnetism as the direct means of locking (magnetic locks)
Let's look at electromechanical locks first. This category represents by far the largest assortment of electrified locks. First, let's analyze how mechanical locks operate.
All electromechanical locks are based on a mechanical locking principle; that is, almost all electromechanical locks are based on a lock that was first a mechanical lock with no electrical components. The exception to this are electric strikes, which have no operating mechanical equivalent. Their equivalent is a manual strike plate. Manual strike plates are simply a bent brass plate that has no operational elements. The elements of a manual strike plate are the faceplate and the strike opening into which the door lock latch engages (Figure 9.1).
Electric Strikes
Electric strikes function by creating an operating element where none existed before. In the manual strike plate, the door latch engages into the strike opening (or pocket). In the electromechanical version there is a strike opening that is engaged and released by a solenoid (Figure 9.2). A solenoid is a small electromagnet that pushes or pulls a plunger that can operate a function. In this case, it holds the strike opening closed or allows the strike opening to swing open, thus allowing the door's lock latch to open without the lock latch being retracted. When a door strike is released, it is possible to pull the door open from the outside while the mechanical door lock latch is still engaged (locked). The strike opening just swings away and there is no longer anything holding the latch in the latch pocket of the frame.
Electrified Mortise Locks
Electrified Mortise Locks are simply standard mortise locks equipped with a solenoid that keeps the latchbolt from retracting (usually only from the unsecure side). That is, the latchbolt can be retracted from the secure side simply by turning the handle, but on the outside of the door, the handle will not turn unless the solenoid is disengaged. This function ensures that anyone inside can get out simply by turning the handle, but outsiders must use a key or electric control of the lock solenoid. Electrified mortise locks typically have a mechanical override function so that they can be opened by using a key or by turning the handle.
Electrified mortise locks (Figure 9.3) are available in either fail-safe or fail-secure modes. In fail-safe mode, power must be applied to lock the lock, whereas in the fail-secure mode power must be applied to unlock the lock. Thus when power to the lock is disengaged “or fails,” the lock will go to its fail-safe (unlocked) or fail-secure (locked) mode. Most electrified mortise locks are ordered as fail-safe.
Electrified Panic Hardware
Electrified Panic Hardware provides an instantaneous means of egress in every emergency along with the ability to unlock the door remotely or by an access control system. Electrified Panic Hardware is available in three locking types (Figure 9.4, Figure 9.5 and Figure 9.6):
• Combines Panic Hardware with an electrified mortise lock
• Panic Hardware with an integral latchbolt to lock against a rim mounted latch plate
• Panic Hardware that operates vertical rods that latch into strike pockets at the top (and often also at the bottom) of the door
Electrified Cylinder Locks
Electrified Cylinder Locks are simple knob sets (no mortise lock) that have a small solenoid inside to control the lock function. They are also available in fail-safe and fail-secure versions. Electrified Cylinder Locks are among the least secure locks available. They cannot withstand even a mild attack of force even without tools.
Magnetic Locks
Magnetic locks are among the most common electrified locks used by the security system industry. This is because they can be fitted onto any door (not always legally) and they require no modifications to the door or frame (although they are a legal modification to the door and frame, which makes them illegal to use on certain types of fire doors). There are two common types of magnetic locks: surface-mounted (Figure 9.7) and shear (usually concealed).
All magnetic locks work by applying an electrical current to an electromagnet (on or in the door frame). There is also an armature (a metal plate) attached to the door. When the door closes, the armature comes into contact with the electromagnet that, when energized, holds the armature (thus the door) tight against the electromagnet.
Surface-mounted Magnetic Locks position the operating surface of both the electromagnet and the armature in a vertical configuration so the armature comes to rest against the electromagnet when the door closes.
Magnetic Shear Locks (Figure 9.8) place the electromagnet inside the top of the door frame with the electromagnet facing down, not against the swing of the door. There is an armature inside a pocket in the top of the door that floats on coil springs and is lifted up by the electromagnet when the door is closed and locked. There have been some problems with these locks over the years when the armature gets misaligned and fails to fall back into its pocket when power is released on the electromagnet, which causes the door to fail to open.
Electrified Dead-Bolts
Another class of electrified locks is Electrified Dead-Bolts. These locks comprise a simple round dead bolt operated by an electric solenoid in the top of the door frame.
Electrified Dead-Bolts (Figure 9.9) are installed similarly to Magnetic Shear Locks; that is, the lock is in the top of the door frame and there is a pocket in the top of the door into which the dead-bolt is received. When the solenoid is engaged the bolt drops into a bolt pocket in the top of the door. When the solenoid is disengaged the solenoid retracts the bolt up out of the bolt pocket in the top of the door. The bolt is magnetized, and the pocket is equipped with a permanent magnet that repels the dead-bolt upward out of the pocket in case the solenoid fails to retract it fully.
These see little use now for safety reasons, but you may run into some that were installed many years ago. The problem with Electrified Dead-Bolts is that if the door becomes misaligned due to building settling or poor door maintenance, the dead-bolt can become jammed inside the bolt pocket in the top of the door, locking all occupants inside the space.
Another version of this lock is a simple, surface-mounted electrified dead-bolt, usually mounted on the door, with a receiver mounted on the door frame. At this time, Electrified Dead-Bolts are only approved for use on storage rooms and other non-occupied spaces.
Paddle-Operated Electromechanical Dead-Bolts
The last class of common electrified locks is Paddle-Operated Electromechanical Dead-Bolts (Figure 9.10). These are rare but can be quite useful in the right circumstances.
They are typically configured with a paddle to unlock the dead-bolts from the inside, allowing for free mechanical egress and work in conjunction with a door position switch so that when the door is closed, the access control panel sends a signal to the lock to re-engage the dead-bolt. Paddle-operated Electromechanical Dead-Bolt locks operate by using a solenoid to throw a lever/cam that rotates the dead-bolts into their locked position. They can be ordered with one, two, three, four, or five dead-bolts, all operated by a single solenoid lever/cam. Thus it is possible to see up to five points of dead-bolts locking a single door. Now that is security! These locks combine very high security with good egress safety.
Lock Power Supplies
Lock Power Supplies (Figure 9.11) supply the power to electrified locks. With these all being electrified locks, somehow it figures that they require an electrical power source, right? Lock power supplies range from the simple to the sublime. First, the simple.
Perhaps the simplest lock power supply can be found on AC-type electric strikes. You can spot these quickly because they “buzz” when they unlock. Where is the buzz coming from, you ask? You can hear it because the solenoid on those strikes (and on AC locks) is operated from alternating current (AC) rather than from direct current (DC). Alternating current reverses its polarity 60 times per second (in the United States — 50 times per second in most other parts of the world). The sound you hear is the solenoid rattling each time the current is reversed. The power supply for AC type electric strikes is nothing more than a simple low-voltage transformer.
Most electrified door locks are operated by direct current (DC). These are nearly silent in most cases. The lock power supply for these locks can range from a simple “Plug-Pack” type arrangement (which includes a low-voltage transformer and a diode to convert AC power to DC), or a more sophisticated arrangement that powers multiple locks. The best of these are enclosed in an electrical cabinet and contain a fuse for the whole assembly, a transformer to convert mains power to low voltage, a rectifying circuit to convert AC power to DC power, individual fuses for the number of locks that the power supply will support, and a terminal strip for connecting the lock power cables to the locks and lock control device(s). Additionally, better power supplies are all rated by a licensed ratings agency such as Underwriters Laboratories (UL), or the European standards association (CE) or rated by the Canadian Standards Association (CSA). They will also have a cabinet lock, and the best are also equipped with a power-on lamp and tamper switch to alert the security system in case anyone opens the cabinet. These should be wired through a metallic conduit to prevent unauthorized tampering with the lock power wiring.
Electrified Lock Wiring Considerations
Electrical devices operate on the principle of Ohm's Law. Ohm's Law is the basic law of electricity. Those who know it well rarely ever have problems with their installations. Those who do not understand it suffer just like those who do not understand gravity. Ohm's Law works on three variables: Voltage (E), Current (I), and Resistance (R). The basic statement of Ohm's Law is E = IR (Voltage is equal to current times resistance). Ohm's Law can also be stated as R = E/I (Resistance is equal to Voltage divided by Current) or I = E/R (Current is equal to Voltage divided by Resistance).
The power supply provides Voltage and Current to a load (Electrified Lock) through a conductor (the wire). This is controlled by a switch (Access Control Panel Lock Relay or Request-to-Exit Sensor). Together, these comprise the electrical circuit. The amount of current that flows through the circuit is equal to the voltage supplied by the power supply divided by the resistance of the electrified lock and the wire. Don't overlook that last part — the wire is part of the circuit and it affects the performance of the lock. Both the lock and the wire present an electrical load (Resistance) to the Power Supply (the source of Voltage). The amount of current flowing through the circuit is equal to the Power Supply's Voltage divided by the total Resistance of the lock and the wire together. Each (the lock and the wire) contributes its own resistance to the voltage.
The lock contributes a certain resistance. So does the wire. The total resistance of the circuit is the resistance of the lock and the wire together. Remember, the lock is rated to operate at a given voltage (usually 12 or 24 volts) and the power supply supplies one of those voltages (12 or 24 volts). We are depending on the wire to present very little resistance or else there will not be enough voltage to operate the lock.
Ohm's Law is important to understanding locking circuits because of a function called Voltage Drop. The greater the resistance of an electrical load the less current will flow. Remember the version of Ohm's Law that said E = I/R (Voltage = Current divided by Resistance)? Here is the critical part. Each part of the circuit “drops” a certain amount of voltage across the entire power supply voltage depending on the amount of resistance of that component. Add more resistance to the circuit and you get less current across the same voltage.
Each wire adds resistance to the circuit, and in wire, resistance is determined by the diameter (cross-section) of the wire (the larger the wire, the lower its resistance; the smaller its wire gauge, the higher its resistance). There is also another factor — the longer the wire, the higher its resistance and the shorter the wire, the lower its resistance.
Remember, both the lock and the wire have their own resistance. Lock Power Supplies are “Constant Voltage” devices; that is, they provide a constant voltage to whatever is connected to them. Their current will vary according to the resistance of the total load (lock and wire combined). The total voltage of the power supply is “dropped” across the total resistance of both the wire and the lock. If the lock requires 12 volts to operate and we are dropping 3 volts across the wire from a 12-volt power supply, that will exactly 9 volts for the 12-volt lock to operate on. This is not enough, so the lock will not operate. We need to drop as close to zero volts across the wire as possible.
Voltage Drop Example
It is essential to understand how to calculate voltage drops to ensure that electrified locks will have sufficient voltage to operate. Let's look at a sample case. Suppose we have an electrified lock that draws 0.3 amps connected to 1,500 feet of 18-gauge wire. From Table 9.1, we see that 18-gauge wire has a resistance of 6.51 ohms at 1,000 feet (at 77 ° F). Then 1,500 feet of 18-gauge wire will have a resistance of 9.765 ohms (6.51 ohms × 1.5). This cable will drop 2.91 volts (6.51 × 1.5 × 0.3 amps = 2.91 volts). If we power a 12-volt lock from a 12-volt power supply we will lose 2.91 volts to cable voltage drop, leaving only 9.09 volts available to power the electrified lock, which is not enough. Most electrified locks have a 10% engineering factor (they will operate at ± 10% of their rated voltage). Thus a 12-volt lock may not operate at a voltage below 10.8 volts (12 volts minus 10%).
Ideally, we would connect the lock to the power supply with very short, very big wires that would add very little resistance. But we often find wire runs that are too long or using wire diameter that is too small to properly power the lock. In practice, the longer the “wire run,” the higher the probability that the lock may not work. Refer to Table 9.1 to calculate the voltage drop across the wire. To do that, add the resistance of the lock and the resistance of the cable (determined by its length) to find the total resistance. Divide the power supply voltage by the total resistance to get the total current. Divide the current by the wire resistance to get the voltage drop across the wire. The amount calculated is the voltage left to operate the lock. It is not enough to use a larger wire diameter or place the power supply closer to the lock. Either method will reduce the effect of wire resistance on the overall circuit.
Electrified Lock Controls
Few contractors or installers spend much time thinking about Electrified Lock Controls, but maintenance technicians know all about them. They get to figure out how to make the thing work after the system stops working due to an improperly configured lock control.
In theory, lock controls should be simple in practice, but in practice, they are not so simple.
It is simple to control a lock — you have an electrified lock, a power supply, and a switch of some sort. Close the switch and the lock energizes as the electrical circuit is completed. Open the switch and there is no power to the lock as the electrical circuit is opened. That is the theory (Figure 9.12).
In practice here is how they actually work:
First Case (Lock Control from the Access Control Panel): This is actually rather simple. The circuit includes the power supply, the lock, the cable, and the relay (electronically controlled switch) that allows power to the lock. All that it takes for this circuit to work properly is to be certain that the power supply is appropriate to the lock, the wire gauge is appropriate to prevent too much voltage drop, and that the Access Control Panel relay is rated to carry the current of the circuit. If the lock circuit presents more current than the relay can support, you can add an “Interposing Relay” to the circuit. An Interposing Relay is a large relay that is controlled by a small relay. Its purpose is to allow a small relay to control a circuit carrying more current than the small relay can handle. Essentially, the small relay (the Access Control Panel Lock Control Relay) will switch the larger (Interposing) relay, which will carry the actual circuit. This may be true, for example, if one relay must control magnetic locks to six doors.
Second Case (Lock Control from the Request-to-Exit Sensor): In this case the circuit comprises the power supply, the electrified lock, the wiring, an Access Control Panel Lock Relay, and a Request-to-Exit sensor at the door. Now, in theory, we have two devices that can control the lock: the Access Control Panel Lock Relay and the Request-to-Exit sensor at the door. However, in practice in most installations we find that the Request-to-Exit sensor is not wired to control the lock directly, instead it is wired to an Exit Sensor input on the Access Control Panel where the sensor switch state is sensed and then the Access Control Panel makes a decision to unlock the door (using the previously mentioned Lock Relay). It also ignores the door-open alarm signal sent by the door position switch when the door is opened. This all works fine — until it doesn't. If the lock is a magnetic lock with no mechanical way to open the lock, and if the Access Control Panel stops working (and yes, that does sometimes happen), there will be somebody locked inside the space because the lock power never got interrupted by the Access Control Panel Lock Relay.
Solution: I recommend using an interposing relay on the Request-to-Exit sensor. In this case, the Interposing Relay is not controlling a larger relay; instead it is providing two contacts (one controls power to the lock and the other signals the Request-to-Exit Sensor input on the Access Control Panel). In this way, it is ensured that the lock will unlock when the Request-to-Exit sensor triggers and the Access Control panel is relegated to bypassing the alarm. It will also interrupt power to the lock, but by the time it figures out to do that, the lock is already unlocked by the Interposing Relay. Everything previously discussed about calculating the correct wire gauge still applies.
Third Case (Lock Control from a remote location, like a Security Console or Desk): In this case, we have a power supply, an electrified lock, and a remotely operated control panel. This may be near to the lock or some distance away, such as in another building. This arrangement is common; for example, at a remote entry door where a visitor may approach the door and use an intercom to call the security console and the lock is opened after interviewing the visitor via the intercom.
• Where the control point is close to the lock, the control can be directly interfaced with the lock power circuit as described with the Request-to-Exit sensor.
• Where the control point is not practical to wire directly, it can be controlled via an Access Control Panel Lock Relay. In this case, the Lock Control Panel switches are wired to the Request-to-Exit sensor of the Access Control Panel and when the Release Button is pressed at the console, the Access Control Panel will release the lock.
• In all cases, comply with codes regarding electrified locks.
Types of Locks Not Recommended
There are some types of electrified locks that I do not recommend using for either security or safety reasons. Let's be clear, this is just one guy's opinion, so you can use these locks at your own risk.
I do not recommend these locks for security reasons:
Electrified Cylinder Locks: Electrified cylinder locks are cute. They pretend to be real locks, but of course they are not in the sense that an Insurance Gecko or Mouse can kick the door open while using these. These locks are so weak that even children have been known to kick through doors locked with cylinder locks. And since electrification adds no strength whatsoever to a cylinder lock, it is still a cylinder lock and is mostly used for humorous rather than security reasons.
Electrified Strikes: See Electrified Cylinder Locks. These might require two mice; otherwise I do not recommend them for the same reason. There are a few high-security electrified strikes, but there are better ways to lock a door in most cases.
I do not recommend (or recommend caution using) the following locks for safety reasons:
Electrified Dead Bolts: Simple Electrified Dead Bolts are an almost sure way to get somebody trapped behind a door. If there is a person and a door and the door is locked with an Electrified Dead Bolt, that person will eventually be very unhappy. Oh, by the way, he will also be the owner of the building or somebody else who can make your life unhappy. If multiple people use the door, the lock will wait until the single most important and angry man in the organization is there before it will fail (permanently … and in the secure mode).
Watch out for Magnetic Locks: Magnetic locks are wonderful. They are simple, reliable, and easy to install. Almost too easy. So they get installed on all sorts of doors that they should not be used on; for example, fire egress doors that already have mechanical panic hardware on them. The installer will ensure that the magnetic locks will always unlock by placing a motion-operated Request-to-Exit sensor above the door, so that when a person comes to the door and pushes on the panic bar, the magnetic locks will already be unlocked. Except that they will not be unlocked. The motion-operated Request-to-Exit sensor will fail, leaving the magnetic locks locked and the person with a stunned look on his face while he pushes on the panic bar. This will happen to the same important angry man who just got locked inside a room last year by an Electrified Dead Bolt. He will be even more important in the organization now because he intimidates everyone in the organization into getting his own way, and of course he just happens to generate millions of dollars in revenue so the organization does whatever he wants. And he is still angry … at you! Or, if he is out of town, this will happen during a fire. Don't use magnetic locks on fire exit doors. And where you do use them always provide at least two methods for unlocking them.
• Magnetic locks can be used with a Request-to-Exit sensor within the panic bar. That would be better, but unlike electromechanical locks, there is no mechanical override for a magnetic lock, so if the Request-to-Exit sensor fails (and everything fails sooner or later), somebody is going to be locked inside. And it will happen to that important angry guy or when there is a fire.
• There is a version of magnetic locks called a “Delayed Egress Lock” that actually meets a specific provision of NFPA 101 for use on fire exit doors. This application combines a magnetic lock with an exit bar sensor, a countdown timer, and a local alarm and signage. The door is usually locked and not used as a normal passage door. It is a special fire exit door, only used in case of an emergency. In case of a fire, power to the lock is integrated into the fire alarm system so that it unlocks automatically, allowing everyone to use the door to exit. In any other emergency, a person can push on the panic bar, holding it pushed for the time delay duration (usually 15 seconds or so; Figure 9.13) as a counter on the magnetic lock counts down to zero. During this entire time, a local alarm is sounding at the door. When the counter gets to zero the lock unlocks and the person can exit the door. Delayed Egress Locks are used to ensure security while still allowing people to exit in an emergency, unless someone is firing a gun at you. Then you're dead.
• Remember, magnetic locks are not free egress locks. Oh, sure somebody will argue that they are used on delayed egress locking systems, and those are on fire exit doors so… Forget it. That is a special case and it requires a Fire Code Variance, and as I said if somebody is trying to get through the door to escape a workplace violence event, well it is not going to be so good for them. Generally, magnetic locks are dangerous because their Request-to-Exit sensors can fail. It is important to provide at least two means of exit sensing with magnetic locks.
• Lastly, Magnetic Shear Locks have been known to jam up in the door as the building settles even when all electronics worked perfectly. I suggest you do not use them at all.
• For the record, I am not saying do not use magnetic locks at all. I am saying that when you use magnetic locks, you must be certain that they fully comply with code and are installed so they will fully accommodate Murphy's Law. Always use at least two means of Request-to-Exit sensing.
• I often couple magnetic locks up with a motion-sensing, Request-to-Exit switch and a latch position sensor in the latch pocket. Neither of these require special knowledge and both are wired in series so that the activation of either one will unlock the lock. Oh, I also use an interposing relay on these so that they both actually interrupt power to the lock as well as sending an unlock signal to the exit sensor input of the Access Control Panel. Belts and suspenders. Keep your pants up.
Chapter Summary
1. All Electrified Locks fall into several categories:
• Electrified Mortise Locks
• Electrified Panic Hardware
• Magnetic Locks
• Electric Strikes
• Electrified Cylinder Locks
• Electro-Mechanical Dead-Bolts
• Combinations of the above
2. These can be further categorized into those locks that provide “free mechanical egress” (just push the bar or turn the handle and go), and those that require some other method to exit:
• Free Mechanical Egress Locks
- Electrified Mortise Locks
- Electrified Panic Hardware
- Electric Strikes
- Electrified Cylinder Locks
• Other Means of Egress
- Magnetic Locks
- Electromechanical Dead-Bolts
• Combinations of the above may fall into either category
3. Electrified locks can be further categorized into two other groups:
• Locks that use mechanical devices to achieve the lock/unlock function
• Locks that use purely electromagnetic means to do so
4. Other categories include:
• Those that can be used with existing door locks and those that must be used alone
• Locks that are visually aesthetic and those that are not
• Locks that sit on the frame and locks that sit in the door
• Locks that work well in emergencies and locks that might be slower to use
• High-security, medium-security, and low-security locks
• Locks that make noise when they operate and those that are nearly silent
• Locks that indicate their lock/unlock status and those that do not
• Fail-Safe Locks and Fail-Secure Locks
5. Electrified locks fit into two broad categories:
• Locks that use electromagnetism to activate a mechanical lock mechanism (electromechanical locks)
• Locks that use electromagnetism as the direct means of locking (magnetic locks)
6. Electrified locks operate on the principle of Ohm's Law.
7. It is essential to understand how to calculate voltage drops to ensure that electrified locks will have sufficient voltage to operate.
8. Basic types of electrified lock controls include:
• First Case (Lock Control from the Access Control Panel)
• Second Case (Lock Control from the Request-to-Exit Sensor)
• Third Case (Lock Control from a remote location, like a Security Console or Desk)
9. Types of locks not recommended include:
• Electrified Cylinder Locks
• Electrified Strikes
• Electrified Dead-Bolts
• Use care when using Magnetic Locks
10. Delayed Egress Hardware can allow the use of Magnetic Locks in conditions where security is high and egress is essential.
1) Electrified Locks are used because
a. Guards at doors are expensive
b. Distributing keys to all authorized users for a highly used door is also a problem
c. Employee turnover makes re-keying costly
d. All of the above
2) Three common types of Electrified Locks include:
a. Electrified Paneled Locks, Electrified Non-Magnetic Locks, Electrified Pin-Grinding Locks
b. Electrified Mortise Locks, Electrified Panic Hardware, Magnetic Locks
c. Electrified Paneled Locks, Electrified Panic Hardware, Magnetic Locks
d. None of the above
3) Locks can be categorized as
a. Free Mechanical Egress Locks
b. Other Means of Egress
c. Both Types
d. Neither Type
4) Electrified Locks can be further categorized into two other groups:
a. Locks that use non-metallic materials and locks that require remote release
b. Locks that allow handicapped people to enter easily and locks that do not
c. Locks that comply with international codes and locks that only comply with local codes
d. Locks that use mechanical devices to achieve the lock/unlock function and locks that use purely electromagnetic means to do so
5) Electrified Locks are
a. Mechanical or electrical devices that hold a door closed
b. Purely electrical devices that hold a door closed
c. Purely electrical devices that unlock a door
d. None of the above
6) Electrified Mortise Locks
a. Are available only in fail-safe mode
b. Are available in either fail-safe or fail-secure modes
c. Are available only in fail-secure mode
d. None of the above
7) Electrified Panic Hardware
a. Provides an instantaneous means of egress in every emergency along with the ability to unlock the door remotely or by an access control system
b. Causes people to panic
c. Keeps people from panicking
d. Automatically opens when people panic
8) Magnetic Locks
a. Are not recommended in occupied areas
b. Are the first choice of every designer
c. Are among the most common electrified locks used by the security system industry
d. Are dangerous and should never be used
9) Electrified Dead-Bolt Locks
a. Are not recommended in occupied areas
b. Are the first choice of every designer
c. Are dangerous and should never be used
d. See little use now for safety reasons
10) Lock Power Supplies always
a. Always make electrified locks buzz when they open
b. Supply the power to electrified locks
c. Should be placed in an area where there is a fire suppression system because they sometimes catch on fire
d. Require constant monthly maintenance
11) Wiring length and gauge must be considered because
a. The total voltage of the power supply is “dropped” across the total resistance of the wire
b. The total voltage of the power supply is “dropped” across the total resistance of the lock
c. The total voltage of the power supply is “dropped” across the total resistance of both the wire and the lock
d. The total voltage of the power supply is “dropped” across the resistance of the wire minus the resistance of the lock
12) Certain Electrified Locks are not recommended for either safety or security reasons. These include:
a. Electrified Cylinder Locks
b. Electrified Strikes
c. Electrified Dead-Bolts
d. All of the above
Answers: 1) d, 2) b, 3) c, 4) d, 5) a, 6) b, 7) a, 8) c, 9) d, 10) b, 11) c, 12) d
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