Wiring Basics 4

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DIY Alarm Systems / DIY Security Systems

Tennessee Alarm Store


Wiring Basics 4

What are Magnetic Contacts (Switches)

magnetic switchAs mentioned earlier, a magnetic contact (switch) is comprised of two parts. A magnet, mounted on the movable door or window and a switch located on the stationary frame. Some switches have leads that are built in and are part of the actual switch. There are concealed switches which are hidden in the door frame and the magnet is concealed in the edge of the door.Window SwitchAlso there are armored switches that are built to withstand a vehicle driving over them. They have armored cables to protect the wires going to the switches and are available in wide gap configurations for loosely fitting doors. The terminals are normally open, but when the magnet is next to the switch they Concealed Door switchare closed. There are models with 3 terminals which give you a choice of using the common and normally closed or the common and normally open contacts. Your alarm panel will most likely accommodate whichever configuration you decide to utilize. I would recommend you not put more than 4 sensors per zone, and only utilize one type, N.O. or N.C., on a zone. This will make Wide Gap Switchmaintenance and troubleshooting much easier to accomplish. Also, if you want to, or need to bypass a zone, you will not have to bypass many more contacts than you originally wish to. Fire zones utilize special cable known as Fire Wire and always require an E.O.L. resistor.

How are Magnetic Switches wired

Wiring these switches is pretty much a straight forward process. There are, in fact, as many as 4 different ways to do this--all of which have their pros and cons. When making wire to wire connections, I recommend soldering them and placing a crimp cap over connection. Give great care to make sure no bare wire is sticking out.

First Method

Wiring Method 1First--If you remember, these switches should be wired as a series circuit when you are placing several switches on a single zone. This can be done with a single wire being run from the "Positive zone" terminal on the alarm panel to the first individual switch. You will connect this wire to either terminal on the switch. You then run a wire from the other terminal on the switch to the next switch, and so on. Finally you end up back at the alarm panel where this wire hooks to the common zone terminal. If you are using an E.O.L resistor, it would be placed in line at the furthest switch from the control panel.

This first configuration has one, serious drawback. You do not have easy access to both sides of the circuit. Troubleshooting is more difficult and you will not be able to easily use normally open circuits. Having everything function off one wire might sound like the way to go, but in reality you are creating work for yourself in the long run.

Second Method

The vast majority of cable used to wire switches is 2 conductor, 22 gauge jacketed cable, sometimes called station wire. This is a somewhat rugged cable because of the jacket covering the inner conductors. The colors of the inside conductors vary and do not matter. We will assume we are using RED and BLACK.

Wiring Method 2Run a length of cable between the alarm control panel and the approximate location of the nearest switch (1). Cut the cable at this location and strip back the jacket and wires. You will need a short piece of the same cable (a pig tail) to drop down the wall if wiring from the attic, or up the wall if wiring from the basement. Connect the two wires from the short cable to each terminal of the switch. Roll off a new piece of cable to go on to the next switch. You now have 3 cables that need to be spliced. The original run from the panel, the continuing run to the next switch and the pig tail that drops down the wall to switch (1). Prepare the remaining ends of the cables and splice the RED wire from the panel to the RED wire of the continuing cable going to the next switch (2). Now connect the BLACK wire from the panel to the BLACK wire coming out of the pig tail (1). The Remaining RED wire from the pig tail gets connected to the BLACK wire of the cable continuing to the next switch (2). Roll off some more cable to go to switch (3). Drop a pig tail down and wire it to switch (2). Again we are left with 3 cables. Wire these exactly the same way you wired the first set of cables at switch (1). Follow the current in the diagram above and you will see this circuit is indeed a circuit wired in series. This may seem confusing at first, but after you wire one switch it becomes fairly simple. Just remember only one path for current and the current must pass through all the contacts.

If you need to utilize normally open devices in addition to the normally closed ones, it is very simple. You simply connect all 3 RED wires and all 3 BLACK wires together and then continue on to the next switch. This is a parallel connection, as you can see from the diagram above. It essentially shorts out the circuit. When you are finished, hook up the RED wire to the positive zone terminal and the BLACK to the common zone terminal.

If you are using an E.O.L resistor, it would be placed in series at the furthest switch from the control panel. The draw back to this method is that the connections are not readily accessible without going up into the attic or down in the basement and can make for troubleshooting or maintenance headaches. That is why all these connections should be soldered to ensure electrical integrity. This is one the most secure methods of wiring and gives you line supervision on the main feed going around the attic or basement.

Third Method (The method I prefer)

Now, I will give you my opinion and ONLY my opinion on how I would wire my panel. You know what they say about opinions...mine and a couple bucks will get you a decent cup of coffee.

If you set up your zones correctly and take adequate precautions with additional detection devices, I think the chances of a thief being able to gain access to your wiring is pretty miniscule. If you are worried about driving a nail in the wall and shorting out a cable there is an easy remedy, which you should do as a matter of procedure. Open each window or door on that zone, one at a time, and listen for the chime or observe on the keypad for indications that all doors and windows are working correctly. You should probably do this once a week anyway.

I like to make individual runs of cable between each switch, on a single zone, and the alarm panel. We call these home runs and that puts all connections, other than the switches, inside the panel (can). They are readily accessible by you for easy maintenance or troubleshooting when required. If you find you have a switch that has gone bad it is easy to jump around it and maintain the system operational until you can replace the switch. The home run cables should be labeled inside the panel so you do not get them mixed up. May I suggest that you use a numbering system rather than writing the location on the wires. Make up an index on a separate piece of paper which you can store in the alarm panel or elsewhere. For example: 1= Zone 1, window N.E. corner Johns room (Instant), 3=Zone 5 motion detector hallway (Interior), 6=Zone 4 front door (Delay) etc.

Wiring Method 3Start by running 2 conductor, 22 gauge cables from the control panel to each switch on an individual zone. Prepare the ends of the cable and connect one end of the cable to the terminals on the switches. At the alarm panel, start with the wire coming from the nearest switch (1) and connect the RED wire to the BLACK wire coming from switch (2). Then take the RED wire from switch (2) and connect it to the BLACK wire of switch (3) and connect the RED wire from switch (3) to the BLACK wire of switch (4). (Are you getting the hang of it.) If you are using an E.O.L resistor and switch (4) was your furthest switch, you would place it between switch (3) and switch (4) as shown. Use shrink tubing on the resistor to ensure it does not short out to the printed circuit board, the other wires or the can. If you have a Volt/Ohm-Meter you can check the wiring by closing all the switches and checking continuity across the RED wire from switch (4) and the BLACK wire coming from switch (1). You should read the approximate value of the resistor or close to 0 ohms if you are not utilizing a resistor. You may now connect the RED wire to the positive terminal of the zone you are using and the Black wire to the common terminal. If you have any sensors that operate on a N.O. circuit you simply connect them across the terminals matching colors. I feel this is the best tradeoff between expense and ease of maintenance or troubleshooting.

4th Method

The 4th method is by far the easiest and the best. You wire one switch per zone and have full supervision of the wiring when you utilize E.O.L. resistors at the switch. The only drawback to this method is it is more expensive than the other methods because of the additional zone expanders needed.

Please read over these methods 1-4 closely and identify which method you wish to use. Once selected, stick with it, and note it somewhere. I might even suggest that you print the diagram associated with that technique and compile all your receipts, diagrams, installation manual, etc, in a notebook stored separately from your can and control panel. Don't make it easy on a thief by providing them with an "owner's manual" for your alarm system. Also, knowing which wiring method you used will be helpful to us if and when you need technical support. I hope this gives you a good understanding of the different methods used to wire zone circuits and how they work. Again if you have any questions may call at 1-423-562-1927 or e-mail us utilizing our Contact Us page. We will be happy to assist you.

Continued on Wiring Basics 5 page.