Electric Power Transfers
To get the wire from the frame into the door to bring power to your new electric latch retraction exit device or other door-mounted electric locking hardware, you will need a door cord, a through-wire hinge or an electric power transfer. See pictures at right.
Door cords are the most vulnerable to vandalism, but the cheapest. They are easy to install: just drill a couple of holes, run the wire through and secure the ends with the caps.
Electric hinges are the most vandal resistant and aesthetically pleasing, but the wires tend to be a little light to accommodate a 16-amp inrush. According to tech support for a major American hardware manufacturer, it is okay to use a standard 24-guage wire electric hinge with a 16-amp inrush device as long as you cut the wires very short. On the other hand it is possible to get 2-conductor through-wire hinges with 18 gauge wires for a few more dollars. A little larger gauge wire will better accommodate the inrush.
Electric hinges fit in the existing hinge prep, so installation consists of drilling a hole in both door and frame to accommodate the wires.
One drawback to electric hinges is that if the door ever needs to be removed, the worker needs to be intuitive enough to realize it is an electric hinge before he drives the pin out of it and ruins it.
Electric power transfers (EPT) are a difficult field install, so it is best by far to order doors already prepped for them, but they are a very durable way to get power from the frame into the door. Also they offer a larger conduit that will hold more conductors – handy if you have a delayed egress exit device requiring 8 or 10 conductors.
Whatever kind of power transfer you use, on the door side, if you have an electric strike or electric mortise or cylindrical lock, you have to drill what is called a “raceway”, that is, a three- or four-foot long hole that will lead from the hinge side to the lock side. Not easy, but not all that difficult, either.
My own technique for drilling a raceway is to pull the door and put it in brackets I make out of 2x4 lumber so that the lock edge faces the floor and the hinge edge faces the ceiling. This allows me to drill straight down, through the width of the door. I find it is much easier to be accurate with gravity on my side. There are also drilling jigs on the market to help you drill a straight hole.
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