Adding FA devices

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Alwayslearningelec

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When you add a smoke detector, strobe etc. to an already wired system how is that done? Can you add in the middle of am extg. loop? I guess you could just remove wires from extg. device run to new device then back to the extg. device. I know reprogramming etc. is required. Thanks
 
Just like any electrical work it depends.

You have to concern yourself with max circuit loading, max loop resistance, zoning etc.

But assuming all that is OK pretty much yes you just add a loop to the existing loop. You cannot (generally) make a simple 'T-Tap'
 
iwire said:
Just like any electrical work it depends.

You have to concern yourself with max circuit loading, max loop resistance, zoning etc.

But assuming all that is OK pretty much yes you just add a loop to the existing loop. You cannot (generally) make a simple 'T-Tap'
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Why would you be adding an extra loop? Wouldn't you add device to extg loop
 
horsegoer said:
Why would you be adding an extra loop? Wouldn't you add device to extg loop
Click to expand...

Let's say you have a hallway (in a school, for example). There are devices on a circuit running down the center of the hallway. Now the customer wants to add a device in one of classrooms off the hallway. How do you do that? If you take down an existing device, you'll see that there is one cable coming in and another going out, "in" generally taken as back toward the panel and "out" being towards the end-of-line device. We might further suppose that the cable is run in RMC or EMT (please, let's not have that discussion here!). If you've picked a device that's next to the classroom, you'll extend the RMC or EMT from the current device's JB to the new location, terminating in a manufacturer's approved mounting means for the new device. Now you pull new conductors or cables from the old JB to the new JB. You'll need four (4). You could use THHN or such, but most alarm installers (as opposed to generalist electricians) will pull 18 to 14 AWG, 2-conductor FPLP. In this case you could use FPL or FPLR, but all you have to do is use the wrong one once and you'll almost never use anything other than FPLP. You also might use a 4-conductor cable, but Siemens, for example doesn't allow it.

Now you lift the incoming cable in the old box off the screw terminals and splice (wire nut, wago, whatever) one pair going to the new box to the old incoming cable, making note of polarity. At the new device, you land the other end of the spliced cable on the "in" terminals of the device. The other pair at the new device you land on the "out" terminals, making note of polarity. This second pair is hanging in the breeze at the old JB. Go back to the old JB and now land the second pair on the "in" terminals of the original device.

Now I've described it this way so you get a feel for how the pairs are arranged. In actual practice, the tech will make all the connections in one box, close it up and make the second set in the other box and close it up rather than going back and forth. You could also make the splice on the "out" side of the old device; dealer's choice. Others here may have their own handy tips and tricks.
 
gadfly56 said:
Let's say you have a hallway (in a school, for example). There are devices on a circuit running down the center of the hallway. Now the customer wants to add a device in one of classrooms off the hallway. How do you do that? If you take down an existing device, you'll see that there is one cable coming in and another going out, "in" generally taken as back toward the panel and "out" being towards the end-of-line device. We might further suppose that the cable is run in RMC or EMT (please, let's not have that discussion here!). If you've picked a device that's next to the classroom, you'll extend the RMC or EMT from the current device's JB to the new location, terminating in a manufacturer's approved mounting means for the new device. Now you pull new conductors or cables from the old JB to the new JB. You'll need four (4). You could use THHN or such, but most alarm installers (as opposed to generalist electricians) will pull 18 to 14 AWG, 2-conductor FPLP. In this case you could use FPL or FPLR, but all you have to do is use the wrong one once and you'll almost never use anything other than FPLP. You also might use a 4-conductor cable, but Siemens, for example doesn't allow it.

Now you lift the incoming cable in the old box off the screw terminals and splice (wire nut, wago, whatever) one pair going to the new box to the old incoming cable, making note of polarity. At the new device, you land the other end of the spliced cable on the "in" terminals of the device. The other pair at the new device you land on the "out" terminals, making note of polarity. This second pair is hanging in the breeze at the old JB. Go back to the old JB and now land the second pair on the "in" terminals of the original device.

Now I've described it this way so you get a feel for how the pairs are arranged. In actual practice, the tech will make all the connections in one box, close it up and make the second set in the other box and close it up rather than going back and forth. You could also make the splice on the "out" side of the old device; dealer's choice. Others here may have their own handy tips and tricks.
Click to expand...

Great explanation. So FA cable can be spliced? Thanks very much for that info
 
I used the term "splice" in a very generic fashion. Always, always, always check the spec. Sometimes the customer won't allow anything except a terminal strip for joining the wire. It can get expensive if you're layout is careless, or field conditions force a lot of splices.
 
iwire said:
In RI no wirenuts allowed.
Click to expand...
Just twist together and tape em up:D

infinity said:
Yes and in NYC it requires 150? C wirenuts.
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Hopefully the FA has already done its job of notifying the building occupants there is a problem before the wirenuts break down from high temperature. Isn't it supposed to tell you when it has sensed a fire relatively early in the fire event and not necessarily tell you 30 minutes later - "by the way there is still a fire"

Besides what good is 150? connectors if the conductor insulation is not 150??
 
kwired said:
Just twist together and tape em up:D

Hopefully the FA has already done its job of notifying the building occupants there is a problem before the wirenuts break down from high temperature. Isn't it supposed to tell you when it has sensed a fire relatively early in the fire event and not necessarily tell you 30 minutes later - "by the way there is still a fire"

Besides what good is 150? connectors if the conductor insulation is not 150??
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'Cause in NYC you have to use LL5 (local law 5) wire, which is rated to 150?C.
 
kwired said:
That would make some sense. I have not done much with fire alarms but doubt the conductors used on what I have seen were rated any more than 90?.
Click to expand...

LL5 wire sucks to work with, specifically because of the insulation.
 
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