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Thread: FA Circuits

  1. #11
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    Quote Originally Posted by luckylerado View Post
    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
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  2. #12
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    Quote Originally Posted by mstrlucky74 View Post
    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.

  3. #13
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    Quote Originally Posted by gadfly56 View Post
    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.

  4. #14
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    Quote Originally Posted by mstrlucky74 View Post
    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.

  5. #15
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    Quote Originally Posted by mstrlucky74 View Post
    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.

    1N73LL1G3NC3 15 7H3 4BILI7Y 70 4D4P7 70 CH4NG3.

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