There is no standard type of wire that is used for garage door safety sensors aside from what the manufacturer’s send out of the box. Since it is only handling low voltage (12 volt), it is almost always thin copper wire.
Delicate little wires can be annoying because they are easy to break. This can happen when you are stripping new ends, or twisting wires together. On older installations, the wire ends may become brittle over time, leading them to break from a minor bump with a broom, ball, garbage can, etc.
But sometimes we find wire that is way thicker than necessary. This is much less likely to get broken, but it does make it more difficult to do a good quality splice, and can be too bulky to connect directly to the terminals on the garage door opener head.
Here are some of the most common types of wire we see out in the field.
Bell Wire
When you buy a new garage door opener or replacement set of safety sensors, it will come with enough “bell wire” to install on a typical 16’ x 8’ garage door. If you see wires run on the exterior of the wall to either the safety sensors or wall control, it is usually this. It is made of a labeled pair of wires, and there is no outer casing to strip away, just the insulation surrounding each copper conductor. Bell wire is usually stiff enough to use with push connectors and wire nuts and is easy to twist together.
UTP
UTP (unshielded twisted pair) comes in many varieties. Types with only two or three pairs of relatively thick wire, like Cat 3 telephone cable, are reasonably easy to work with. But other types, such as Cat 6, are made up of up to six pairs (12 individual strands) of extremely delicate little wires that are easy to break, difficult to strip, and don’t work well with most common connectors. They can even be broken by overtightening the screw terminal where it connects to the opener or directly to the sensor (Genie/Overhead Door).
If you are tinkering around with UTP wiring, do yourself a favor and take a picture of the existing connections before you get started. With a dozen little wires to choose from, losing track of which wire goes with which can ruin your day.
When working with UTP cable it is best practice to treat each twisted pair as one wire – take them apart, strip away the insulation, and twist back together. That pair then forms an individual wire. It will be much stronger this way.
Don’t try to use push connectors with the more delicate type of UTP, the wire will bend and not make a solid connection. Use a twist connection instead.
It is critical to be extremely careful when stripping UTP. The outer case will have to be removed, and it is easy to cut too deeply and damage one of the conductors when you do this. Go slow, and use proper wire strippers! Same when you strip the insulation away from each individual strand of wire. You should closely inspect the copper conductor to be sure that it hasn’t gotten nicked before making your splice. Even a tiny nick can lead to the wire breaking when you twist it, or if it gets bumped at some point in the future.
Thermostat Wire
Thermostat wire has the opposite problem from Cat6 UTP – it is too thick and rigid. This presents two problems.
First, it is difficult to join two wires of significantly different thickness. Any improperly performed splice between bell wire and thermostat wire is a potential trouble spot down the road. I recommend a twist and tape connection here, but be sure to do it right.
Second, the result of splicing two or three pieces of thermostat wire together is that the end will be too big to fit into the wiring terminals on the opener. You may have to splice in another piece of bell wire in order to reduce it down to a size that can be attached to the opener.
Speaker Wire
You may even come across braided speaker wire being used for safety sensors, especially if you are the proud owner of an antique Stanley garage door opener. It is easy enough to work with, just be sure to twist the stripped braided ends together tightly so they are easier to join with other wires or opener terminals.