Splicing Alarm Circuits Guide

By Ari Erenthal, Published Apr 23, 2017, 08:00pm EDT

Alarm installers commonly connect multiple sensors to a single zone. They do this by splicing the wires together. In this report, we will explain how alarm technicians splice the most common alarm wires, including:

  • What a splice is
  • Common alarm wire types - solid and stranded
  • Splicing stranded wires
  • Splicing solid wires
  • Parallel splices 
  • Series splices
  • When to choose parallel splices
  • Two videos demonstrating splices

What Is A Splice?

To splice a wire is to touch the conductive portion of two wires together. This allows the electrons in a circuit to freely flow together. Alarm technicians commonly splice wires leading to different sensors together. This allows the sensors to share a single circuit. In theory, any number of sensors can be added to a single circuit. In practice, every sensor adds more resistance to the circuit. 

Common Alarm Wire Types - Solid and Stranded

Alarm installations commonly use a mixture of wire types, depending on the type of sensor and the type of circuit. Powered devices such as motion detectors and acoustic glassbreak sensors often use solid wires, commonly 4/22, with the detection circuit being carried on one pair of wires and power on the other. 

Magnetic contacts tend to be grouped together and need a wire that adds less resistance and is easier to splice, so alarm installers often use stranded 18/2 for these circuits. Sirens and strobes generate a large amount of resistance, and are commonly wired with stranded 18/2. 

Different Wires Are Spliced Differently

In order to make a permanent connection, wires are twisted together and then covered. Splices add resistance to circuits, especially as time goes on, because exposing the copper to the elements causes it to oxidize. Incorrectly spliced wires are a common cause of false alarms and other alarm malfunctions. In these two videos, we will show you some methods of splicing wires so that they will not have to be redone after a decade of use.

Splicing Stranded Wires

Stranded alarm wires, which tend to be thicker, should be bent over and then crimped. Splices in dry locations can be covered with electric tape. Splices in humid locations should ideally be soldered. We demonstrate this in the video below:

 

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Comments (11)

Aww man, what happened to the good ol' 'Twist n Tape'?

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Sure, if you don't mind going back for a service call every decade or so. Less if it's a harsh environment. 

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Sure, if you don't mind going back for a service call every decade or so.

RDR - Recurring Decennial Revenue 

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Well, there are real consequences to false alarms. More and more jurisdictions are enacting false alarm fines.

Just as worryingly, a flaky alarm zone could make a subscriber to just stop using their alarm out of convenience. Now they're no longer protected. If they get robbed and the zone was bypassed or the alarm wasn't armed, what happens? Your company gets a bad rap, that's what, because you've just taught all their neighbors that an alarm won't protect them from robbery. 

And if the user gets into the habit of not using their alarm, they'll start wondering why they're paying for monitoring. Now your attrition rate goes up. Best case scenario is you get to fight an uphill battle to convince them to retain their monitoring subscription, starting with diagnosing and repairing their alarm for free. Worst case scenario is your customer retention tricks don't work and now they go badmouthing you to all their friends and social media connections. 

The problem with bad splices is that they cause alarms to malfunction in unpredictable and erratic ways, at a random time in the future. And the user doesn't know that it's due to installer error, they just know that sometimes the alarm goes off for no apparent reason. Alarm must be broken, right?

Bad splices are bad for business. 

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Bad splices are bad for business.

Sure, but a well done western union splice, even if not soldered is

  1. Stronger than the wire itself
  2. Improves electrically over time, due to cold metal flow

Though I concede U1 might not have had the WU in mind when he said twist and tape.  It is a bit of a skill and is slower than other methods.

 

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I use to do this, but with solder and heat shrink. I would also tin stranded wires for panel terminations.

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In practice, every sensor adds more resistance to the circuit.

Doesn't it depend on whether it is wired in series or parallel?

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Good question. The sensor by itself adds resistance to the circuit. That resistance can be reduced by wiring it in parallel, but that's a function of the circuit design. But it is factually true to say that every device attached to a circuit slows the current down, which is why you need to make the decision to wire in series or in parallel. 

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The sensor by itself adds resistance to the circuit...

To me, that's a strange way of putting it, in that adding usually implies aggregation, not isolation.  But I'm probably just looking at it too hard :)

I can agree it adds a resistor to the circuit (in the ordinal sense).

But it is factually true to say that every device attached to a circuit slows the current down...

How do you mean "slows down", as in actual time of something?

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Sorry guys I know that's the way you guys like to do stuff in the states. But here in Australia it's one device per zone(unless its zone doubled) and solder and heat shrink. In my opinion this is the best way to splice.

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Not alowed in Belgium, one zone is one detector. Only exception are magnetic contacts, you can have five of those on a single zone (basically to accomodate a single window with different panes).

IF you splice cables together: solder of tampered junction box

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