Please assist me with how the NEC would apply to these conditions. Thanks in advance for your assistance.
We finish basements using a wall system that is similar to structural insulated panels. The panels are 3 1/2" thick with a 1/2" cement board panel on the face and 2 1/2" of foam insulation adhered to the cement board. The foam insulation backs up to the concrete basement wall when it is installed. These panels go in very quickly and have many advantages over traditional drywall and stud construction.
Each panel has a 1 1/4" chase bored horizontally through the panel at the height of outlets and switches These chases are to be used to fish wires between the panels. The horizontal chases are more than 1 1/2" behind the face of the panels, so protection for the wires is typically not needed. There is no PVC or metal conduit for these wire chases. NMB wire is typically used for the wiring.
NEC 334.30 states that wires must be supported every 4.5 feet and within 12 inches of boxes. However, 334.30 (B) offers an exception that non-metallic shielded cable will be allowed to be unsupported when the wire "Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable." I think that this has been interpreted to apply to premanufactured panels as well.
My questions are:
1. Does exception B apply because these are pre-manufactured panels or because supporting is impracticable?
2. Is there another exception supporting/securing the wiring that I do not know about that could apply to this situation?
3. If an exception does not apply to this situation, can you suggest methods of securing and/or supporting the wiring that would be acceptable under the code.
4. Would the answers to any of the above questions be different if the chase for running the wire was not a 1 1/4" chase completely surrounded by foam, but was a 3/4" deep channel cut horizontally into the back of the foam in which the wire is tucked into and held in place by friction. In this case the top of the channel remains open after the wiring is installed.
Again, thanks for your help.
We finish basements using a wall system that is similar to structural insulated panels. The panels are 3 1/2" thick with a 1/2" cement board panel on the face and 2 1/2" of foam insulation adhered to the cement board. The foam insulation backs up to the concrete basement wall when it is installed. These panels go in very quickly and have many advantages over traditional drywall and stud construction.
Each panel has a 1 1/4" chase bored horizontally through the panel at the height of outlets and switches These chases are to be used to fish wires between the panels. The horizontal chases are more than 1 1/2" behind the face of the panels, so protection for the wires is typically not needed. There is no PVC or metal conduit for these wire chases. NMB wire is typically used for the wiring.
NEC 334.30 states that wires must be supported every 4.5 feet and within 12 inches of boxes. However, 334.30 (B) offers an exception that non-metallic shielded cable will be allowed to be unsupported when the wire "Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable." I think that this has been interpreted to apply to premanufactured panels as well.
My questions are:
1. Does exception B apply because these are pre-manufactured panels or because supporting is impracticable?
2. Is there another exception supporting/securing the wiring that I do not know about that could apply to this situation?
3. If an exception does not apply to this situation, can you suggest methods of securing and/or supporting the wiring that would be acceptable under the code.
4. Would the answers to any of the above questions be different if the chase for running the wire was not a 1 1/4" chase completely surrounded by foam, but was a 3/4" deep channel cut horizontally into the back of the foam in which the wire is tucked into and held in place by friction. In this case the top of the channel remains open after the wiring is installed.
Again, thanks for your help.