Electrifying A Mortise Lock To Secure Conference Room

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.

COMMAND ACCESS ML91
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.