A garage door alarm contact is a magnetic switch used to connect a roll-up or overhead garage door to a home security system. It consists of a switch and a magnet, just like any standard door or window contact used for an alarm system. The biggest difference is that an overhead door contact is built into a rugged housing to handle the vibration, heat, and cold of the hostile garage environment.
Not everyone needs a garage door contact. In fact, most alarm owners don’t include the garage roll-up door in their main house alarm system plans. There are some good reasons for this, not the least of which is everyday convenience.
Even if you don’t want the garage door to generate actual alarm signals, most alarm systems allow you to program a door contact to act as a simple “garage door open” sensor. This avoids any chance of a false alarm and police response, but still lets you know the status of the garage door.
Check out this page on the pros and cons of connecting a garage door contact to a home alarm system to see if you should install an overhead door switch.
If you do decide to connect your garage door to the alarm system, choosing where on the door to install the switch is an important consideration. See this page on the best overhead door contact mounting locations for details on how to do this the right way.
For sectional garage doors, I recommend using a contact that fastens to the track or rail of the door. Check out the Sentrol Garage Door Sensor - Track Mount Model 2315.
For a more reliable and trouble-free installation, check out the following tips to get the best results from your garage door alarm contact.
It’s important to use the correct screws and/or bolts and nuts to install a garage door alarm switch. Most garage door sensors aren’t packaged with mounting hardware. Even when hardware is included, it may not be suited to your installation.
The biggest challenge in securing a garage door alarm contact is vibration. Even the smoothest running garage doors have some vibration, and many have a LOT.
Use lock washers on screws and bolts to keep them from working loose. Machine bolts with nylon bushings are also available, and work very well.
If you need to mount an alarm magnet in thin metal, use a scrap of aluminum strip as a reinforcing backer. This will give the fasteners something solid to connect to, and prevent loosening later.
After final tightening of mounting hardware, add a dab of caulking where screws, bolts, and nuts meet their mounting surfaces. This gives an extra bit of insurance against the fasteners vibrating loose.
With normal wear and tear, garage overhead door parts often become loose and don’t fit as well as they did when they were new. If the garage door panels shift from side to side during opening or closing, they may cause the garage door alarm switch or magnet to be damaged.
Avoid this by giving generous clearance between the alarm switch and magnet and any brackets, cables, and other stationary objects. Allow a minimum of ½” of spacing to anything near the path of the magnet as the door moves. If needed, right angle L-brackets and Z-brackets can be bought or fashioned to give added clearance.
Many garage overhead contacts are factory-built with armored cabling,
which helps avoid snagging and crushing damage. The Honeywell 958 and
several Seco-Larm contacts have armored cabling.
If you’re using an alarm company you can ask them to install this type of contact, if they have it available. For DIY security alarms, just be sure to choose armored leads when you buy your alarm equipment. This adds slightly to the cost, but is well worth it if it prevents even a single repair or replacement.
If your garage alarm contact didn’t come with armored cabling, it can be
added to regular wire leads. Flexible armor shielding is sold in bagged
coils several feet long, and can be cut to length and slipped over the
factory alarm switch leads. Cut the armor with regular tin snips or a
hack saw, and clean up the cut end with needle-nose pliers and a file.
Even with armor, the wiring to the alarm switch can get snagged on objects moving past. This usually ends in the wiring parting company with the switch. Needless to say, this will render the switch useless…
Avoid this disaster by making sure the alarm cable is fastened every
couple of inches to a solid surface. Metal and/or plastic clips, along
with screws, make this easy to do.
Hopefully, these garage security tips for overhead alarm contacts will help you achieve a trouble-free installation that lasts for years.