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Re: Grounds and Neutrals
To add clarification to Richards post "Exception: Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor." regarding the "parallel conductors" part.
From the NEC. (bold is mine - note that none of the exceptions apply)
- 310.4 Conductors in Parallel.
- - Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, neutral, or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends to form a single conductor).
- - - Exception No. 1: As permitted in 620.12(A)(1) .
- - - Exception No. 2: Conductors in sizes smaller than 1/0 AWG shall be permitted to be run in parallel to supply control power to indicating instruments, contactors, relays, solenoids, and similar control devices provided
- - - - (a) They are contained within the same raceway or cable,
- - - - (b) The ampacity of each individual conductor is sufficient to carry the entire load current shared by the parallel conductors, and
- - - - (c) The overcurrent protection is such that the ampacity of each individual conductor will not be exceeded if one or more of the parallel conductors become inadvertently disconnected.
- - - Exception No. 3: Conductors in sizes smaller than 1/0 AWG shall be permitted to be run in parallel for frequencies of 360 Hz and higher where conditions (a), (b), and (c) of Exception No. 2 are met.
- - - Exception No. 4: Under engineering supervision, grounded neutral conductors in sizes 2 AWG and larger shall be permitted to be run in parallel for existing installations.
- - - - FPN: Exception No. 4 can be used to alleviate overheating of neutral conductors in existing installations due to high content of triplen harmonic currents.
- - - The paralleled conductors in each phase, neutral, or grounded circuit conductor shall
- - - - (1) Be the same length
- - - - (2) Have the same conductor material
- - - - (3) Be the same size in circular mil area
- - - - (4) Have the same insulation type
- - - - (5) Be terminated in the same manner
- - - Where run in separate raceways or cables, the raceways or cables shall have the same physical characteristics. Conductors of one phase, neutral, or grounded circuit conductor shall not be required to have the same physical characteristics as those of another phase, neutral, or grounded circuit conductor to achieve balance.
- - - - FPN: Differences in inductive reactance and unequal division of current can be minimized by choice of materials, methods of construction, and orientation of conductors.
- - - Where equipment grounding conductors are used with conductors in parallel, they shall comply with the requirements of this section except that they shall be sized in accordance with 250.122.
- - - Conductors installed in parallel shall comply with the provisions of 310.15(B)(2)(a).
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