FA Circuits

[mstrlucky74]

Class B fire alarm system. These two devices on same loop/circuit and it’s a full conduit job. No need for two pipe out of device. You can have the in and out cabling in the same pipe, correct? One pipe would be fine as I drew in as long as you have junction point correct? Also , can you have IDC and NAC circuits in same pipe? Thanks.

 

[gadfly56]

Class B fire alarm system. These two devices on same loop/circuit and it’s a full conduit job. No need for two pipe out of device. You can have the in and out cabling in the same pipe, correct? One pipe would be fine as I drew in as long as you have junction point correct? Also , can you have IDC and NAC circuits in same pipe? Thanks.

For Class B you can run the feed and return for a device in the same pipe.

For IDC and NAC, as a general rule you can run them in the same pipe as well. Check with the fire alarm panel vendor to be sure. I will say, as a matter of practice, it's not a good idea, unless you have a very long run where absolutely nothing will now, or in the future, branch off. It only takes a couple of times having to pull all the wire out of a pipe back through a couple junction boxes or so to see the wisdom of separate pipes for IDC's and NAC's. You can't ever just pull half the cables out. It was a lesson I don't need to be taught twice.

 

[mstrlucky74]

For Class B you can run the feed and return for a device in the same pipe.

For IDC and NAC, as a general rule you can run them in the same pipe as well. Check with the fire alarm panel vendor to be sure. I will say, as a matter of practice, it's not a good idea, unless you have a very long run where absolutely nothing will now, or in the future, branch off. It only takes a couple of times having to pull all the wire out of a pipe back through a couple junction boxes or so to see the wisdom of separate pipes for IDC's and NAC's. You can't ever just pull half the cables out. It was a lesson I don't need to be taught twice.

Thanks.

 

[mstrlucky74]

One other thing. The modules( that are on same circuit as smokes) get M and Z type...one cable for power . It only shows the Z(power) from the module to the waterflow so I'm not sure id that Z cable goes all the way back. I was going to ask if it could be in the same pipe as the M(data loop).

 

[mstrlucky74]

For Class B you can run the feed and return for a device in the same pipe.

For IDC and NAC, as a general rule you can run them in the same pipe as well. Check with the fire alarm panel vendor to be sure. I will say, as a matter of practice, it's not a good idea, unless you have a very long run where absolutely nothing will now, or in the future, branch off. It only takes a couple of times having to pull all the wire out of a pipe back through a couple junction boxes or so to see the wisdom of separate pipes for IDC's and NAC's. You can't ever just pull half the cables out. It was a lesson I don't need to be taught twice.

BTW, class B there is no return.....just in and out as I assume that's what you meant.

 

[luckylerado]

One other thing. The modules( that are on same circuit as smokes) get M and Z type...one cable for power . It only shows the Z(power) from the module to the waterflow so I'm not sure id that Z cable goes all the way back. I was going to ask if it could be in the same pipe as the M(data loop).

They type Z cable should terminate at the AIM device. It would not go all the way back to the panel.

On your original post. Single devices can have both send and return in the same conduit even on a class A circuit.

 

[gadfly56]

BTW, class B there is no return.....just in and out as I assume that's what you meant.

At the junction box, you have to go either right or left. If you go left, you need a pair in and a pair out so you can go back across the junction box and catch the strobe (or whatever it is) on the other side. If that second strobe is not the end-of-line, you'll need yet another pair to go back into the junction box and then back up the feeder pipe to its next destination.

 

[gadfly56]

They type Z cable should terminate at the AIM device. It would not go all the way back to the panel.

On your original post. Single devices can have both send and return in the same conduit even on a class A circuit.

True, but there are restrictions. I didn't want to confuse the issue.

 

[luckylerado]

True, but there are restrictions.

There are. It is important to know the exceptions to the separation rules for sure. I see, and have been guilty of, a lot of wasted time and material before studying up on this.

 

[sameguy]

I normally bid and pipe the jobs as class A, for the main pipe run, only in/out for the short distances; helps in pulling the wire and trouble shooting start up.

 

[mstrlucky74]

They type Z cable should terminate at the AIM device. It would not go all the way back to the panel.

On your original post. Single devices can have both send and return in the same conduit even on a class A circuit.

Thanks...So if you had a full conduit job what would determine which way you ran the conduit in this instance(see pics). Two devices on wall.....you could go in and out with two conduits or you could put j-box above device so you only need one conduit from device. Either way would work and I'd think the one conduit would be better/easier install. Thanks

 

[gadfly56]

Thanks...So if you had a full conduit job what would determine which way you ran the conduit in this instance(see pics). Two devices on wall.....you could go in and out with two conduits or you could put j-box above device so you only need one conduit from device. Either way would work and I'd think the one conduit would be better/easier install. Thanks

So, this is a bit of thread drift, but...

Unless the devices are more than 12" wide, picture #2 would not make any sense, assuming these devices are hanging on a wall, because the minimum separation for feed and return is supposed to be 12" for vertical runs. However, to single devices, the code allows you to put the feed and return in the same pathway. This makes sense, since at worst if you break that path you lose only one device and apparently the committee felt that was a reasonable compromise. What you didn't illustrate is drop down to device 1, run directly across to device 2 and then go up again, which is what you might get if you came in the left side of the junction box the device is mounted on and then went out the right side of the box. You might consider that "pure" Class A. I should note that the distance between device 1 and device 2 has to be greater that 12" or you violate the spacing requirements.

There are additional exceptions and requirements, but I'd suggest you crack open NFPA 72 and meditate a little.

 

[mstrlucky74]

So, this is a bit of thread drift, but...

Unless the devices are more than 12" wide, picture #2 would not make any sense, assuming these devices are hanging on a wall, because the minimum separation for feed and return is supposed to be 12" for vertical runs. However, to single devices, the code allows you to put the feed and return in the same pathway. This makes sense, since at worst if you break that path you lose only one device and apparently the committee felt that was a reasonable compromise. What you didn't illustrate is drop down to device 1, run directly across to device 2 and then go up again, which is what you might get if you came in the left side of the junction box the device is mounted on and then went out the right side of the box. You might consider that "pure" Class A. I should note that the distance between device 1 and device 2 has to be greater that 12" or you violate the spacing requirements.

There are additional exceptions and requirements, but I'd suggest you crack open NFPA 72 and meditate a little.

Thank you. If class B I don't understand feed/return. Just one circuit(feed) out to EOL usually....no???? Class A has a return.

 

[gadfly56]

Thank you. If class B I don't understand feed/return. Just one circuit(feed) out to EOL usually....no???? Class A has a return.

"Feed and return" as in using the junction box as the starting point.

 

[luckylerado]

Thank you. If class B I don't understand feed/return. Just one circuit(feed) out to EOL usually....no???? Class A has a return.

True except class A is more about servivability of the circuit and separation. I try to put a return on class B circuits instead of an EOL as a best practice whenever possible. To me it is worth the effort to ensure as many devices stay online as possible during a fault or break but simply running a return does not make a circuit class A. More like a B+ . It is easy to imagine a scenario where a fault or open circuit condition is created on a loop but several days pass before a technician can respond to trouble shoot and clear the issue. If this happens on in the middle of an SLC circuit with 100 smoke detectors and pull stations in a hotel for example, having a return is the difference between a system that will continue to work through the fault and a potential fire going undetected in half the building. If I know a building has onsite or on-call qualified maintenance I do not worry about it so much but using the hotel again as an example, I know that the front desk staff is really good at silencing that supervisory alarm between check-ins.