markthompson9591
Member
- Location
- Houston Texas
can you run #8 parallel conductors for 24vdc
Just as a matter of interest, what would be the objection?is it a NEC application? if so, in general the answer would be no.
Just as a matter of interest, what would be the objection?
310(H) Conductors in Parallel.
(1) General. Aluminum, copper-clad aluminum, or copper
conductors, for each phase, polarity, neutral, or grounded circuit
shall be permitted to be connected in parallel (electrically
joined at both ends) only in sizes 1/0 AWG and larger where
installed in accordance with 310.10(H)(2) through (H)(6).
Exception No. 1: 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, or for frequencies of
360 Hz and higher, provided all of the following apply:
(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.
(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. 2: Under engineering supervision, 2 AWG
and 1 AWG grounded neutral conductors shall be permitted
to be installed in parallel for existing installations.
Informational Note to Exception No. 2: Exception No. 2 can
be used to alleviate overheating of neutral conductors in existing
installations due to high content of triplen harmonic
currents.
(2) Conductor Characteristics. The paralleled conductors
in each phase, polarity, neutral, grounded circuit conductor,
equipment grounding conductor, or equipment bonding
jumper shall comply with all of the following:
(1) Be the same length
(2) Consist of 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
(3) Separate Cables or Raceways. Where run in separate
cables or raceways, the cables or raceways with conductors
shall have the same number of conductors and shall have the
same electrical characteristics. Conductors of one phase, polarity,
neutral, grounded circuit conductor, or equipment
grounding conductor shall not be required to have the same
physical characteristics as those of another phase, polarity,
neutral, grounded circuit conductor, or equipment grounding
conductor.
(4) Ampacity Adjustment. Conductors installed in parallel
shall comply with the provisions of 310.15(B)(3)(a).
(5) Equipment Grounding Conductors. Where parallel
equipment grounding conductors are used, they shall be sized
in accordance with 250.122. Sectioned equipment grounding
conductors smaller than 1/0 AWG shall be permitted in multiconductor
cables in accordance with 310.104, provided the
combined circular mil area of the sectioned equipment
grounding conductors in each cable complies with 250.122.
(6) Equipment Bonding Jumpers. Where parallel equipment
bonding jumpers are installed in raceways, they shall
be sized and installed in accordance with 250.102
can you run parallel two or three #8 thhn condutors for 24vdc that is the largest wire possible for power distribution board (92 amp bus rated 60 degree C) will take
Perhaps I could have phrased my question better.With few exceptions the NEC prohibits using conductors smaller than 1/0 in parallel.
see pdf attahed
Perhaps I could have phrased my question better.
When Petersonra commented about it being an NEC application, I took from that, that it would not be NEC compliant.
So, perhaps better worded, why does the NEC prohibit it?
Is there any technical basis for doing so?
That's what I'm thinking....... If this one was all in one box - nobody would question it.
Agree.If in two boxes split, between the Power Distribution Block and Power Distribution Panel, with an NEC conduit between them - someone could. I'd still tend to install per the drawing - unless I had an AHJ rep standing on me.
I do not know the answer, I have read that one problem with paralleling small conductors is that small differences in length effect the splitting of the current flow possibly resulting in an overload on one of the conductors.
If you look at one of the exceptions you can see that the OCPD for those installations must be in line with the ampacity of a single conductor. It seems this exception is in place to allow small conductors to be paralleled for voltage drop reason and not additional ampacity.
FWIW, this appears to be the template for specific install and could be revised for use. Additonally, one title block reads...I think it is non-compliant.
The drawing says it is for approval. I would not approve it.
see pdf attahed
One additional question.
One comment.