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Keeping RCBOs Neat In A CU


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#1 cjard

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Posted 13 March 2016 - 09:20 PM

RCBOs. Wonderful things, but they come with a couple of tails that apparently, you aren't supposed to cut. My spark just cuts them to length, but does anyone have any brighter ideas fid organising the excess cable inside the cu so it's neat, and I can sway his behaviour?

#2 Nickfromwales

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Posted 13 March 2016 - 09:43 PM

Leave him carry on. I cannot see any reason not to cut the excess off the tails. Usually just the neutral and sometimes also a wafer thin earth lead.
Due to my marine panel wiring experience, I routinely left way too much ' re-termination ' slack in my CU's, to a point once when my good sparky mate refused to give me a sign off. He told me to cut back and re-make the cables to the breakers as there was too much of it :(.
Panel wiring, particularly on large ships, taught me to go around the perimeter of the CU at least once before cutting the tails to their respective terminations. Domestic wiring, it seems, doesn't favour my old habits :).
IMHO, excess slack = problematic CU. Not saying cut it short, but they can be cut nevertheless. ;)
Regards, nick.

#3 ProDave

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Posted 13 March 2016 - 10:10 PM

If you really want a neat solution try this:

Attached File  compact rcbp.jpg   45.88K   28 downloads

Dual busbar for L and N into the bottom of the rcbo's.

I only know of one suplier of these and he's strictly trade only.

#4 Nickfromwales

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Posted 13 March 2016 - 10:52 PM

Now that's a way to shave off a good bit of grief :). Are the rcbos 'specific' to that CU?
Regards, nick.

#5 jsharris

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Posted 14 March 2016 - 07:45 AM

I thought our Crabtree CU, with it's plug-in RCBOs was neat, but it's still very crowded with all the neutral and earth tails going up to the top bars, making it tight to get even the 9 circuits we've got in it.

I wonder why that very neat double busbar system isn't more common? It looks like it'll fit any standard width MCB or RCBO, as long as you don't get RCBOs with the pre-attached neutral. My pet gripe with those is that they use very thick (around 10mm²) cable for the neutral lead, even on the smaller 6 A RCBOs, which makes for a lot of clutter in there, even though they use very flexible silicone insulated wire.

#6 ProDave

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Posted 14 March 2016 - 08:08 AM

My gripe is WHY do they need the silly little earth lead? (and why is in not green / yellow)?

"grown up" rcd's or rcbo's manage without an earth wire. I presume it's foir the test button to create a leakage to earth, but other types or rcd and rcbo simply put a resistance from one side of the sensing coil to the other to create an imballance without the need for an earth connection.

That compact board I only know of from one supplier. He imports the components and makes the CU's to your specific requirements. but as I say he's strictly trade only.

P.S I cut the fly leads to length to tidy tjhings up a bit.

Edited by ProDave, 14 March 2016 - 08:09 AM.


#7 Nickfromwales

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Posted 14 March 2016 - 08:27 AM

Also strange that an all rcbo board I did last year had earth fly leads on some and not on others, varying with current rating of the rcbo !
:wacko:

#8 jsharris

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Posted 14 March 2016 - 08:33 AM

All of mine seemed to have about a yard of thin white earth wire on. I think they have the earth just to make it easier internally to wire the test resistor, as they can tuck it away from the main sense coil and switch area, which is pretty tight for space.

#9 cjard

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Posted 14 March 2016 - 09:53 AM

Dave, apparently cream is the nominated colour for an earth lead of that type, not green/ yellow

I see comment that cutting the leads off shorter is ok but they then need a new ferrule crimping on because the wire is too finely stranded to resist being destroyed by the neutral bar screw. That could be the leading cause of CU fires that led the inappropriate driving force of LFB to pressure for the inappropriate hash that is amendment 3! :)

#10 Alphonsox

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Posted 14 March 2016 - 03:00 PM

I take it that this is an SBS CU ? I can't quite see from the photo

#11 djvasey

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Posted 14 March 2016 - 07:44 PM

I had the same issue with a 19 way Wylex CU which has 19 RCBO's , I contacted Wylex technical and they confirmed it was fine to modify the leads, a power screwdriver should not be used however. Regards David

#12 Nickfromwales

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Posted 14 March 2016 - 09:14 PM

Good point about the bootlace furrels :). Left my very expensive crimper in Porto :(. Used to use loads of them when panel wiring, and makes a nice neat job of things too.
I tend to twist 3 or 4 of those small wires into one and then double the end over before screwing the earth terminal tight.
;)

#13 ProDave

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Posted 14 March 2016 - 09:55 PM

View PostAlphonsox, on 14 March 2016 - 03:00 PM, said:

I take it that this is an SBS CU ? I can't quite see from the photo
Yes that's an SBS board.

Re the fine earth wires, I twsit a load together and put them into one terminal with a boot lace ferule. There are simply not enough earth terminals to put each of those silly little wires into one terminal and well as an earth terminal for each circuit.