How to Coordinate Automatic Doors with Locking Devices
This article discusses low energy power operators on doors that swing. It does not discuss automatic sliding doors or high energy power operators.
Often doors need to be secured, and increasingly often these doors need to also be equipped to provide assisted access for persons with disabilities. Assisted access if accomplished through the use of a device called an automatic door operator, automatic door opener or power operator.
The first rule of operation for doors that must both lock and automatically open is: “If the door is opened automatically it must lock electrically.” In order for the door operator to open the door, the door must first be unlocked. If it must be unlocked only when the power operator is performing its task, this must be done through electric locking devices. This article is about how to arrange for that to happen.
What Kind of Lock?
Currently there are at least four kinds of locking devices that can be used in swinging automatic door applications:
- Electromagnetic locks
- Electric strikes
- Exit devices with Electric Latch Retraction
- Aluminum door electrically released mortise latch locks
The part of a lock that prevents a door from opening is usually called a ‘deadbolt,’ ‘deadlatch’ or ‘latch.’ When a door is required to close and lock automatically, this is usually accomplished by using a deadlatch. When an automatically deadlatching lock is present, before a power operator can open the door, this deadlatch must be released. It is not enough to unlock the lever or doorknob. The latch itself must be released to enable the power operator to open the door.
Locking System Ready Power Operators
Many low energy power operators come equipped not only to open the door, but to also unlock the door. These greatly simplify the wiring as well as the thought processes of the installer. A couple of examples are the LCN 4630/4640 series and the new Norton 6000 series. Both offer ease of wiring because they both handle all the auto-operator function wiring “in-house” – that is, all the wiring that coordinates the unlocking and opening and closing and locking of the door is done inside the cover of the power operator.
Circuit board diagrams for the LCN 4600 and Norton 6000 series are shown below:
In both examples the principles are the same: both offer a 24-volt powered output to control an electric strike or a form-C contact to control a device (such as an exit device with electric latch retraction) that has its own power supply. Both have terminals for accessories: actuators (usually large, heavy square or circular switch plates engraved with the wheelchair symbol and/or text such as “PRESS TO OPERATE DOOR”), motion sensors, presence sensors, fire alarm input, etc. To use these terminals it is important to understand what their intended purpose is.
Inputs, Outputs and Dry Contacts
With very few exceptions, most automatic door openers require an external power source. For both of the above examples and the vast majority of commercial grade products on the market, the input voltage is 120-volt house current.
Usually power operators come with two inputs for actuators anticipating that users will be activating the power operator from either side when they are coming in or going out. That is why most of the time two actuators are specified for each power operator. The most common exception to this is when the exterior actuator is an access control – keypad, key switch, card reader, etc. Another exception is when a request-to-exit switch placed inside an exit device acts as the actuator upon egress. Still another exception is when a passive infrared motion detector is used as an actuator. Anything that can be used to momentarily close a set of open electrical dry contacts can be used as an actuator.
Actuators can be wireless or hard wired. Hard wired actuators have a momentary contact, normally open switch on board. They are connected via 2-conductor wire to the actuator inputs. When activated, they close the contact signaling the power operator to begin the opening cycle.
Wireless actuators run on batteries (usually 9V) and communicate via radio frequency with a wireless receiver that is connected in turn to the power operator. When the wireless actuator is activated it causes the wireless receiver to momentarily close a set of contacts. The contacts on the wireless receiver are either connected an actuator input on the power operator control board or the power operator has inputs specifically designated for the wireless receiver input. Wireless receivers require power that is usually supplied by a powered output on the power operator board.
An access control system can also act as an actuator, so that persons using the automatic door opener can do so using their access control credential. As illustrated in the 900-4RL wiring diagram later in this article, a request to exit switch inside an exit device can also be used to actuate a power operator.
Safety or as presence sensor inputs connect to presence sensing devices that signal the power operator that a person is in the path of the opening or closing door. Their purpose is to stop the power operator from hitting people with the door by signaling it to interrupt its current operation until the way is clear of pedestrians. The safety sensors signal the power operator to resume its operation when the person is no long present in the path of closure.
Wireless Receiver Input
A wireless receiver acts the same as an actuator except it requires power. Some power operators provide a designated connection for the wireless receiver and others diagram how it can be connected to the board as an actuator and receive power from a powered output from the control board.
Powered, or "wet" outputs typically output direct current (DC) low voltage (12 or 24 volts) to power an electric strike and/or wireless receiver. Connecting a device to a wet output is the same as plugging an appliance into a switched electrical outlet. Therefore make sure the power operator is disconnected before wiring anything to a wet output.
When an electric strike is connected to the powered output the power operator acts as both transformer (reducing 120 volt house current to usually 24 volts DC) and switch, activating the electric strike before beginning the door opening/closing cycle. This is by far the easiest way to coordinate an electric locking device with a power operator.
Sequential Operation Output
If your power operator has a Sequential Operation Output, this output allows one power operator to control another power operator. Typically this option is used when there are two consecutive doors: an exterior door that opens onto a vestibule, and an interior door. It allows the installer to 'program' the power operators to open one after the other or simultaneously.
Power operators may come equipped with two kinds of outputs: powered outputs and form C relay dry contacts (illustrated above, fail safe wiring).
To use the dry contacts on the power operator control board to control an electric locking device, run one conductor from the negative output terminal of an external power supply directly to the locking device or other device requiring power. Run a second conductor from the positive output of the power supply to the Common terminal of the form C contact. Run a third conductor from either the N.O. (Normally Open) or N.C. (Normally Closed) terminal depending on whether you have a failsafe or fail secure locking device. The power operator is already set up to change the state of the relay when it is signaled to open the door; therefore it will either power or un-power the electric locking device before it begins the open/close operation cycle.
Externally Controlled Power Operators
Some power operator units rely on an external controller to interface locking and automatic opening functions. Typically this controller is a low voltage power supply equipped with a special relay board. One such set-up is the Schlage PS914 power supply with 900-4RL option board, designed to control power operators and Von Duprin electric latch retraction exit devices as shown below:
As shown in the wiring diagram above,
Another example of an external controller that can be used to coordinate a power operator with a locking system is the Security Door Controls UR-1 module:
The wiring diagram above shows the UR-1 board wired to coordinate operations of the actuator, door operator and locking device, in this case Security Door Controls' LR100 series aftermarket electric latch retraction kit.
Both the 900-4RL and the UR-1 as shown in the above diagrams are set up to accomplish most or all of the functions of a fully equipped, locking system compatible power operator control board in situations where the power operator is not so equipped.
My purpose in publishing this article is to help demystify the interactions of power operators and locking systems. Because of the timing and number of electrical connections inherent in these interactions, installation can sometimes be daunting. +
It is vital that installers pay close attention to the installation instructions when installing power operators because incorrect installation can cause serious injury or death. It is not a project for beginners. Even if you are experienced in door closer installation, if you have not installed a power operator before it would be a good idea to observe someone with experience install one before you attempt it.
Questions & Answers
What happens in a power cut? How do doors open with no power?
In the case of a swinging door, the door can be opened manually. Sliding doors are often equipped to “break away” and be pushed open.