This is a commonly asked question on this and other forums. Hopefully this thread will provide some answers. Input from other professional electricians is always welcome.
First let’s look at NEC Article 100, Definitions;
Cabinet. An enclosure that is designed for either surface mounting or flush mounting and is provided with a frame, mat, or trim in which a swinging door or doors are or can be hung.
Cutout Box. An enclosure designed for surface mounting that has swinging doors or covers secured directly to and telescoping with the walls of the box proper.
Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.
Panelboard. A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.
A panelboard is designed to be installed inside of a cabinet or cutout box. Therefore, it is physically impossible to splice “inside” a panelboard.
So the question now becomes “can a cabinet or cutout box be used for splicing”. To answer that question we need to look at NEC Article 312, Cabinets, Cutout Boxes, and Meter Socket Enclosures.
312.8 Switch and Overcurrent Device Enclosures with Splices, Taps, and Feed-Through Conductors. The wiring space of enclosures for switches or overcurrent devices shall be permitted for conductors feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices where all of the following conditions are met:
(1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross-sectional area of that space.
(2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.
(3) A warning label is applied to the enclosure that identifies the closest disconnecting means for any feedthrough conductors.
The answer is “yes, splices can be made inside of a cabinet or cutout box” as long as the three above conditions in NEC 312.8 are met.
The next question asked is if the panelboard is removed from the cabinet or cutout box, can the wiring be spliced in the remaining enclosure and extended to the new panelboard location? The answer is yes as long as all three conditions in NEC312.8 are met including #3, which states that a warning label is applied to the enclosure indentifying the closest disconnecting means.
Is the door required to be screwed shut? No, not an NEC requirement.
Finally, if the cabinet or cutout box is used to extend the existing circuits to the new service location there are a few things that need to be done;
1. Remove the neutral bar and extend the neutral conductors through to the new location.
2. The equipment grounding conductors need to be extended through, but make sure the ground bar is still bonded to the enclosure.
3. The existing equipment grounding bar needs to be grounded back to the new service. The wire size shall be based on the largest overcurrent device protecting the branch circuit spliced in the existing enclosure.
4. Multiwire branch circuits can be used to extend existing circuits, but be aware of AFCI and GFCI concerns and circuit breaker requirements.
5. The grounding electrode system will have to be re-routed to the new service location without splices, or spliced using an approved means.
6. All unused openings will need to be effectively closed with approved means.
As always, all comments are welcome!
(V)
First let’s look at NEC Article 100, Definitions;
Cabinet. An enclosure that is designed for either surface mounting or flush mounting and is provided with a frame, mat, or trim in which a swinging door or doors are or can be hung.
Cutout Box. An enclosure designed for surface mounting that has swinging doors or covers secured directly to and telescoping with the walls of the box proper.
Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.
Panelboard. A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.
A panelboard is designed to be installed inside of a cabinet or cutout box. Therefore, it is physically impossible to splice “inside” a panelboard.
So the question now becomes “can a cabinet or cutout box be used for splicing”. To answer that question we need to look at NEC Article 312, Cabinets, Cutout Boxes, and Meter Socket Enclosures.
312.8 Switch and Overcurrent Device Enclosures with Splices, Taps, and Feed-Through Conductors. The wiring space of enclosures for switches or overcurrent devices shall be permitted for conductors feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices where all of the following conditions are met:
(1) The total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross-sectional area of that space.
(2) The total area of all conductors, splices, and taps installed at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.
(3) A warning label is applied to the enclosure that identifies the closest disconnecting means for any feedthrough conductors.
The answer is “yes, splices can be made inside of a cabinet or cutout box” as long as the three above conditions in NEC 312.8 are met.
The next question asked is if the panelboard is removed from the cabinet or cutout box, can the wiring be spliced in the remaining enclosure and extended to the new panelboard location? The answer is yes as long as all three conditions in NEC312.8 are met including #3, which states that a warning label is applied to the enclosure indentifying the closest disconnecting means.
Is the door required to be screwed shut? No, not an NEC requirement.
Finally, if the cabinet or cutout box is used to extend the existing circuits to the new service location there are a few things that need to be done;
1. Remove the neutral bar and extend the neutral conductors through to the new location.
2. The equipment grounding conductors need to be extended through, but make sure the ground bar is still bonded to the enclosure.
3. The existing equipment grounding bar needs to be grounded back to the new service. The wire size shall be based on the largest overcurrent device protecting the branch circuit spliced in the existing enclosure.
4. Multiwire branch circuits can be used to extend existing circuits, but be aware of AFCI and GFCI concerns and circuit breaker requirements.
5. The grounding electrode system will have to be re-routed to the new service location without splices, or spliced using an approved means.
6. All unused openings will need to be effectively closed with approved means.
As always, all comments are welcome!
(V)