The 80A Wylex RCD in my new consumer unit
has 2 connections top, and 2 bottom.
Is it OK to wire
the Live input to the top,
the Neutral input to the bottom,
the Live output to the top,
and the Neutral output to the bottom
The inputs will come from the main switch in the consumer unit
(there are 2 RCDs in it)
(and there will be a 100ma 100ms RCD before this consumer unit and the others)
Why would it short the supply?
I thought that a RCD connects the 2 blues and 2 browns,
and measures that the current is the same in both
and disconnects both if there's an imbalance.
I'm unsure of whether swapping the blues from top to bottom
would short everything out and why?
That's why I asked,
I want to understand electrics more,
and have a better than professional job at the end of it!
(I got my A level physics many decades ago!)
The other poster misunderstood your proposal. However, the way you
want to do it the balanced currents in the neutral and live wires would
be going in opposite directions so would amount to an imbalance equal to
double the current drawn. That is, the tiniest load would trip the RCD.
i dont think it would short out -
top left neutral in would go to bottom left neutral out
and bottom right live in to top right live out -
and then on to the mcbs
so when its turned off both would be disconnected.
100 ma RCD is because there are lots of old circuits and consumer units
On Monday, September 26, 2016 at 5:42:27 PM UTC+1, DICEGEORGE wrote:
The typical operation of an RCD is that the live poles are wound one way
round a ferrite core, while the neutral poles are counter-wound on the
same core, so cancelling each other out until some leakage happens ...
if the live goes top to bottom while the neutral is bottom to top, I'd
expect the windings would add rather than cancel and the RCB trip instantly?
I'm not familiar with the insides of a modern wylex, can you not feed
one of the wires behind the DIN strip so they both run top to bottom?
On Monday, September 26, 2016 at 8:11:10 PM UTC+1, Andy Burns wrote:
that's the way to do it.
I was thinking of minimising cable wire length
but much simpler to do it your way,
thinking of myself or another trying to understand the wiring ten years later!
So it doesnt matter if both inputs to an RCD are at the top or at the bottom.
That's right isn't it?
I wasnt swapping the wires left and right,
but up and down,
there would still be blue wires on the left and brown on the right
but one input would be on top and the other at the bottom.
Theoretically the RCD would work, wouldn't it?
pps i probably wont do this as its confusing
Rather than ramming three thick cables into a single terminal, I'd take
the N output of the main switch up to the right hand neutral bar, them
take individual neutrals from there to each of the two RCDs and then
from the outputs of those to the other two neutral bars.
Looks like the photoshopping accidentally shows the output neutral on
the RCDs coming from the live outputs?
maybe have another stab at drawing it?
On Monday, September 26, 2016 at 9:32:36 PM UTC+1, Andy Burns wrote:
(but the end of the 3 blue wires are already squashed together somehow
and were when I got the unit.
But the main swqitch got dust in it,
then i took a few years to replace it
and forgot where the wires had been originally!)
OK that is a 17th edition "high integrity CU"... it provides for three
separate load areas - one without RCD protection, and two further ones
each with their own RCD.
ISTM you want two neutral tails leaving the lower right terminal of the
main switch - one goes to the top right neutral bus bar, and the other
to the top right terminal of the right RCD. Another neutral shares that
terminal and goes to the top right terminal of the left RCD.
The bottom right terminal of the right RCD goes to the middle bus bar,
and the bottom right terminal of the left RCD goes to the leftmost
neutral bus bar.
The bottom left terminal of the main switch feeds the top left terminal
of the right hand RCD (you could also have a live bus bar comb in there
for non RCD protected MCBs or RCBOs). The top left terminal of the right
RCD also connects to the top left of the left RCD.
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