|
[email protected] wrote:
|> |
[email protected] wrote:
|> |>
|> |> | Mount a four hole lug of appropriate size on an insulating stand off,
|> |> | bug the three conductors onto a short pigtail off of the breaker using
|> |> | spit bolts or insulating displacing connectors as appropriate, use an
|> |> | insulated multi tap block to join the four conductors to the jumper from
|> |> | the breaker... There is always a code compliant way to do it. You just
|> |> | have to invest the time or the money in hired expertise to find out what
|> |> | that way is.
|> |>
|> |> If I would approve of things like pigtails and splices, I'd just run some
|> |> 600 kcmil from the main breaker down a raceway and splice off each of the
|> |> 4/0 feeds into the 3 panels they go to. But my intention is to absolutely
|> |> avoid splicing (having seen the mess when they fail). I believe the risk
|> |> is less by just stranding the 4/0 into 2 adjacent holes on the same lug.
|> |> Or can you show me code that says not to split stranded wire into two holes?
|> |> I'm not convinced about the "fracturing" issue since this will involve less
|> |> mechanical stress on the wire than typical wire bending that takes place in
|> |> typical panels, especially if I use the larger box that would be needed to
|> |> put all those pigtails below the breaker.
|> |>
|> |
|> | 110.3 Examination, Identification, Installation, and Use of Equipment.
|> | (B) Installation and Use. Listed or labeled equipment shall be installed
|> | and used in accordance with any instructions included in the listing or
|> | labeling.
|>
|> So basically, you can't figure out a better way to do it.
|>
|> At this point I will now ignore all followups that do not have a constructive
|> solution not involving splices, pigtails, or other unsecured connections.
|>
|
| Undoubtedly because they are code compliant and your method is not.
| Would you mine explaining how an insulated terminal block is an
| unsecured connection?
Your description of why not to mix current carrying conductors in the
same hole ...
| It is the thermal cycling of the current carrying grounded conductor
| (neutral) that makes having it in the same termination as the Equipment
| Grounding (bonding) Conductor (EGC) an unsafe practice electrically.
| There has yet to be devised a terminal that can use one pressure
| producing part to maintain good electrical contact with two conductors
| that are thermally cycling at different rates and times. If you look at
| the breakers that are listed to hold two separate conductors you will
| see that the conductors are separate from each other and the screw has a
| pressure washer under its head. The addition of the pressure washer or
| plate allows solid contact between both conductors and the plate into
| which the screw is threaded. The pressure washer will flex sufficiently
| to permit unequal thermal cycling without the connection failing.
|
| In thirty years of electric work I have seen many connection failures
| caused by improper torquing of connections and by using a single
| terminal to terminate multiple conductors. The reason that it is safe
| to use a single terminal to terminate multiple EGCs is that they do not
| carry current during normal operation and they are not subjected to
| repeated thermal cycling.
... would just as readily apply to phase conductors as well as the
neutral. If you have 2 or more different loads (hence different
thermal cycling characteristics) fed by different conductors in the
same hole, the same problem will occur. A pigtail is thus like that.
Maybe this is why pigtails have failed. Your earlier post further
reinforces my intent to avoid all pigtails with 3 or more conductors
(those with 2 will be avoided as well, but your post doesn't really
reinforce my intent against those).
But I hardly would consider putting a 600 kcmil and 3x 4/0 together
on the same pigtail. Maybe cad-welded ... maybe.
As for a terminal block, how is it any different than a lug on a circuit
breaker, other than taking up even more space. How is it that a terminal
lug would be safe enough to be listed as a terminal block and not as part
of a circuit breaker?
A friend of mine is a metal machinist. Perhaps I'll just have the exact
lug needed manufactured for me.
BTW, did you know that a common practice when 2 more more panels are
needed in parallel is to put 2 wires in the lugs, one coming from the
service entrance metal, and the other going to the 2nd panel? What I
wonder is if you would cringe at that? I would. Yet it is common,
and has the same issue you explained before. But I will be avoiding
such a thing.
