Electrifying A Mortise Lock To Secure Conference Room

April 1, 2008

Conference/meeting rooms for many corporations have become high tech. Video and audio equipment including large screen high definition televisions, touch sense boards and conferencing equipment come at a high cost. Because many of these products are standalone and relatively portable, security has become a necessity. For this reason, it has become very important to control entry into these rooms.
I was invited to the installation of a Command Access Mortise Lock, Model ML91, a Concealed Door Loop and a SW8 Power Supply onto one of the entrance doors to a conference room in a multi-building facility. Another company would install the reader mechanism.

Important: The wood door and metal jamb were not fire rated, permitting electrification without re-certification and re-labeling.

Normally the positioning of the lock would not be a point of discussion. However, for this installation, the solid core wood door was equipped with a narrow window positioned towards the lock side running approximately half the height of the door. Commonly known as a vision lite, this type of window is mounted into the door using a non wood frame. On another type of window- equipped door, known as a “French Door,” a French door window is secured using wood molding, having a similar appearance to the panes of glass secured into the show side of a multi-pane wooden window frame.

It is important to know if the door is equipped with a window because it can and in this installation does affect the positioning of the mortise lock. The centerline of the mortise lock in this door is located at 37 inches above the finished floor. This is lower than most installations where the lock is located about 42 inches above the finished floor. The reason is the vision lite is relatively long, extending from the upper portion of the door to beyond the middle. This design affects the position of mortise lock but probably would not affect a cylindrical lock installation other than the aesthetics.

Note: According to the 2001 California Building Code, 11133B.2.5.2 Hand-activated door opening hardware shall be centered between 30 inches (762 mm) and 44 inches (1118 mm) above the floor.
The middle butt hinge for a 7’0” x 3’0” door is mounted in the normal position 44” above the finished floor. This butt hinge is seven inches higher than the centerline of the mortise lock. This requires a diagonal raceway.

The raceway will be drilled using a 3/8” diameter carbide tipped drill bit, four feet long. A strip of painter’s masking tape will be positioned on the face of the door at the appropriate angle. The tape provides a gauge to align the drill bit so the raceway is at the approximate centerline of the mortise pocket.

The decision was made to install an electrically unlocked mortise lock. To be able to use the existing trim, the Command Access ML91 was chosen. This mortise lock will be a storeroom function lock that is a direct door prep replacement for the mortise lock on the door. No modification will be required to install the electrified mortise lock.

The ML91 is available Fail Safe (electrically locked) or Fail Secure (electrically unlocked) as a 12 or 24 VAC/VDC mortise lock operating at 700mA@12V or 350mA@24V. Mortise lock power consumption is approximately eight watts. Electrified mortise locks can be ordered with status monitoring switches including Latch Bolt, Solenoid, Door Position, Security Monitoring and/or a Request to Exit (REX) switch depending upon model. The only option available for the ML91 is Request to Exit.

The electrified lock will operate on 24VDC and is equipped with a Fail Secure configured solenoid. In addition, this lock is equipped with REX. The additional features determine the number of wires connected to the electrified lockset. Only two wires, one positive and one negative, are required to power the solenoid in order to lock and/or unlock the latch bolt. Two additional wires are required for the REX feature. With the REX feature, four conductor-20 gauge cable will be used for the 30-foot wire run.

Note: Command Access recommends using gray PVC jacket cable for added protection when installing a Concealed Door Loop.

The ML91 comes with a bridge rectifier pigtail that plugs onto the power leads. A bridge rectifier changes Alternating Current (AC) into Direct Current (DC). For this installation, the pigtail is not necessary, as the power supply will provide filtered and regulated DC.

A Command Access SW8 solid state 4.8A regulated 24VDC power supply was installed. The SW8 is capable of powering up to eight lock mechanisms. This power supply incorporates dry contact switching, resetable fuses, fire alarm link, independent short circuit detection, adjustable output voltage (22 to 27 volts under load) and thermal overload sensing. In addition, SW8 power supply has battery backup capability.
The additional power was required for the reader/release mechanism and for future electronics to control access for the additional entry doors into this conference room.

To complete the electrical connection between the jamb and door, a power transfer system is required. For this installation, a Concealed Door Loop (CDL) was chosen. The stainless steel CDL is a flexible armored conduit designed to transfer low voltage power from the source through the jamb and door to the locking device. Because it is not a hinge, the CDL can accommodate larger gauged wires, up to an eight wire-18 gauge jacketed cable. The inner diameter of the conduit is .268”.

When the door is closed, no part of the Concealed Door Loop is visible. When the door is open, all that is seen is a short conduit and two end caps. The CDL can be mounted in any position along the edge of the jamb and hinge side of the door. The CDL can even be installed onto a door and jamb equipped with a continuous hinge. For this installation, the CDL will be mounted through the center butt hinge.
Note: Because the CDL is not easily seen, there can be little concern for finish in order to accommodate the door hardware.

To complete the installation, the Concealed Door Loop had to be installed, the wire run from the power supply to the mortise lock and the wire run from the momentary switch to the mortise lock.
The Concealed Door Loop was installed through the middle butt hinge. Five-eighth inch diameter holes had to be drilled through each leaf of the middle butt hinge for the rounded ends of the flexible armored conduit. To ensure good alignment of the holes through each leaf, the screws were removed from the door leaf. One screw was removed from the jamb leaf and the door leaf was closed against the jamb leaf. Then a longer screw went through the door leaf, into and through the jamb leaf and secured the two leafs against each other.

The end cap is then positioned onto the leaf in an unobstructed position. A center punch was used to locate the center for the end cap hole. Try to avoid drilling through any of the screw holes. Once the position is determined, drill a 5/8” diameter hole through both leaves and into the jamb frame. Remove the screw securing the leaves. Secure the leaf to the door edge.

To provide room for any movement of the flexible armored conduit as the door is closed, drill a 5/8” diameter hole three inch deep through each leaf into the door core and the jamb. This way as the door is closed, there will be sufficient room for the conduit. Use a vacuum to remove any debris from the drilled holes. Use a de-burring tool to remove any sharp edges.

Prepare the butt hinge for Concealed Door Loop end caps. Position the end caps into the drilled holes. Adjust one so the mounting holes are vertical and the second horizontal. Mark the positions. The end caps must be positioned in this fashion, as the screw head must not contact each other.

Drill the mounting holes using a 3/32” diameter bit. Tap the drilled holes using a 4-40 tapered tap. Clean out the drilled holes to insure a clean installation.
At this time, run the wiring from the power supply through the wall and out of the 5/8” diameter hole in the jamb. Slide the wire through the Concealed Door Loop and into the door’s raceway out the mortise pocket. Leave sufficient wire.

Install the Concealed Door Loop using the supplied four Phillips Head screws. Open and close the door to be certain the loop retracts into the jamb and door core.

The final step is to wire the electrified mortise lock. Two wires, one red (positive) and one black (negative), power the solenoid. Two wires will be run from the momentary switch in the conference room to the Request to Exit switch in the mortise lock case.

The mortise lock power wires have a pigtail containing a bridge rectifier. The bridge rectifier is needed if the power supplied operate the lock is AC. For this installation, the power supply produces DC. Cut the bridge rectifier off the pigtail. Wire the mortise lock.

Test the operation of the mortise lock and the Request to Exit to be certain the power supply and lock are operational.
More and more companies will begin to or continue to incorporate electromechanical locking mechanisms. Not only do these lock mechanisms control access, but also many of the system available provide audit control, meaning the ability to not only know when someone gained access, but be able to know who gained access.

For more information, contact your local locksmith wholesaler or Command Access Technologies, 2386 East Walnut Avenue, Fullerton, CA 92831. Telephone: 888-622-2377. Fax 888-622-2302. Web Site: www.commandaccess.com