On Fri, 25 May 2018 22:19:24 +0100, John Rumm wrote:
Non-combatant here, but I can't see anything going into the neutral of the
main switch. Could be the angle of bend, of course.
Assuming that the red and black in grey sleeving is the feed from the
meter, they seem to be one position out; I would expect black to be over
the 'N' and red over the 'L'.
I can't really make head nor tail of the red/black/blue/brown wiring.
To show how little I know, shouldn't everything be fed off the live and
neutral bus through the main switch? In which case why are the two 63A RCDs
linked by wires over the top?
What is the function of the furthest left thick blue wire? It seems almost
to go down behind the CU; if not it is in the live of the main switch
which means it can't be isolated (I think).
Last lot of electrics I used a professional!
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64
It's a split-load board, so there are several neutral busbars - one for
each RCD, and one for the non-RCD circuits. It looks like this board has
three, and I *think* they're wired correctly. The neutral out from the
main switch (hidden by the camera angle) goes to the first busbar, top
left. As there are no non-RCD circuits, no circuit neutrals should go to
this busbar, but the input to the two RCDs is fed from it. The cable
goes to the neutral in of RCD 1, then across to the neutral in of RCD 2.
The terminal on RCD 1 may be over capacity, and two separate links from
the busbar would be better, but without seeing the instructions for this
board I don't know if it's how it's supposed to be wired. The neutral
outputs from the RCDs then go to the other two neutral busbars. The
circuit neutrals have to go to the right busbar, or the RCD will trip.
The live cable from the output of the main switch looks like it goes
behind the rail to the top of RCD 1, then is linked across to RCD 2. The
outputs of the RCDs feed the busbars under the black cover, which feed
It's surprising given the rise of RCDs that CUs still rely on linking
cables to connect up the RCDs. In fact with RCBOs becoming more
common, I would have thought there's a market for an RCBO-only board
with both live and neutral busbars along the bottom and no link cables
One thing I did notice is that the MCBs aren't in order. I was always
told to put the highest rated MCBs next to the switch and then work
down, but the 6A MCBs are in the middle of each group.
I'm pretty sure it's just the camera angle hiding it. There are four
thick blue cables going off the top of the picture. The leftmost one
disappears behind the main switch, and could loop into the bottom of it
without being seen - look how little of the blue cable is visible below
the first RCD . Also if you look carefully there's a brown cable coming
up from the top of the first RCD (behind the one that loops to the
second RCD). It's mostly hidden behind a bunch of blue cables, then
comes down behind the brown cable that goes to the 40A MCB and
vanishes behind the breakers - I can't see where this can be going if
not to the main switch.
Sadly the camera angle prevents me coming to a definite conclusion, but
there might be half a dozen errors with the feed to the RCD or none.
Assuming those are 25mm2 incoming sheathed tails, nominal 11mm dia and
using Gimp to measure cable sizes from the other parts.
Those non meter interlinks are 16mm2? If so, then 2 into the top left
RCD N IN is OK as those usually take 35mm2 max (in the few Hager devices
I've had). If 25mm2, then that terminal is over capacity.
Gimp suggests they have an OD of 8.4mm +/- 0.5mm so 16mm2 if sheathed,
but could be 25mm2 if single insulated.
Where's the other half of the ring on the 1st and 3rd from left B32?
That looks like a 2.5mm2 conductor so underrated for a B32
Rightmost B32 looks like 4mm-6mm2 so must be a non ring circuit I guess.
Left B40 looks 4-6mm2 based on estimated OD, less than 10mm2 so under
rated for a 40A circuit.
=======================OK sir, what's my score?
How many did I miss? (Don't say what, I'll have another look)
But give the bloke a plus point for bothering with flexi grommit strip
on the rear entries, even though one has started unravelling.
It may be I'm misled by the camera angle but it looks to me as if the
neutral is bridged from the first RCD to the second RCD, so Gordon
Bennet knows what's going on at the 3 neutral terminals. Perhaps it's
too obscene for Adam to show in the photo ;)
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