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Posted By Topic: Wiring circuit breakers in Rackmounted Panels

Nov 18 2014 00:44

I have a 3u(rack unit) distribution panel, which has enough space for 10 double pole circuit breakers. All breakers are in one row. The first breaker will be the main breaker for isolation of the panel and the rest will feed the loads in the field.

I believe there are two ways of wiring it:
1) The line cable enters the bottom of the Main CB, the top of the CB is connected to a comb/spur busbar that goes across all 10 CBs. The field cables will be connected to the bottom of each circuit breaker.

Pros- Faster to complete
Cons- Supply is on bottom of first CB, but then on top of all other CBs, so no consistency.

2) The line cable enters the bottom of the Main CB, a brown core and blue core connect from the top of this main CB to the bottom side of the second CB. The bottom of the second CB is also connected to a comb/spur busbar that goes across 9 CBs. The field cables all connect to the top of each circuit breaker.

Pros- Power supplied on same side of CB so consistency.
Cons- A bit more wiring involved.

Also, some people have a preference of connecting line cables to the top of each circuit breaker, to minimise risk of the wire falling out if it were on the bottom of the CB.

What's everyones preference, 1 or 2?

Nov 18 2014 15:08

Isn't it a requirement that breakers be fed either all from the top or all from the bottom? Or is that just good practice? I've looked for that clause though and I can't find it, so perhaps I'm making it up. All I can find is the section to do with breaker orientation (i.e. all must be either up when on or down when on).

Nov 18 2014 17:23

You will find with the modern boards and RCD requirements you will always get the inconsistency. Mostly people feed the top of the main switch and from there feed the top of all RCD devices. From the bottom of the RCD you then feed the 3 circuit breakers. You also feed the hot water circuit breaker to the bottom from the main switch and the oven, hob, ac and any other circuit breakers not needing RCD protection. there is nother ways of doing it but this way keeps it simple and allows the use of the pre fabricated busbars for most circuit breakers and allows the use ofmultiple 6mm feeds from the first main switch busbar to feed all the RCD. The last board I wired in had 5 rcd circuits of 3 breakers.

Nov 18 2014 17:59

What he said... There's no right way or wrong way, just whatever way works for you, and is safe. RCD's make it hard to keep all feeds to top, or bottom, unless you want endless tails running all round the board.

Mar 09 2018 17:33

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