RCBO's

[bornagainsparkie]

Some great reading and tips in this forum and nice to bounce idea's of other parties.

I am just fitting an RCBO for the first time, no instructions so would someone confirm, disagree or inform.

I understand the principles of RCBO's but have never wired one and I intend to install in a stand alone enclosure replacing a 30 amp rewireable fuse (BS3036) which has been supplying a shower on a 6mm cable, so for my simple mind, I want to confirm that "FE" means that this part is connected to Earth or not and that the floating neutral can be connected directly into a splitter (if that's the term used) the live is also is taken from the splitter (obviously not the same splitter) and then the outgoing is fairly obvious.

The RCBO is a Wylex NSBS40/1


Many thanks

Hello again,

Re: my subject RCBO's, I note there have been a few viewings but no response which suprises me as I note there are some clever informed people out there, judging from the responses to other questions.

Come on it's not a trick question, does "FE" Mean earth connection? this is new terminology to me even though I am qualified to C&G Parts 1 & 2 albeit a few hundred years ago!

The way I see it, this is the control side to earth but would like verification, can't find it on manufactures web site!


Many Thanks

_________________________________
moderator

please note 10 a

 

[felix]

I can't give you a simple answer but I can tell you how the things work (I designed the innards for an MK RCBO back in 1988) and this might enable you to work it all out.

An RCBO has Neutral In and Out as well as the usual Live In and Out. It's looking for any unbalance between the currents in these two conductors. The MK one passed both wires through a simple current transformer then used the output from this to fire a triac and trip the standard CB which is also in there. It had a test button which connected Live Out to Earth through a resistor. I expect they all work along similar lines.

To make it work, all current going out through the live wire MUST return through the neutral wire (but you probably know that already). An earth connection is needed for a test button. That's about it. If you can identify all you L and N ins and outs and have only FE left over then I suggest it stands for frame earth. No doubt somebody out there will put me right if it doesn't.

 

[plugwash]

it stands for functional earth and is named as such because it is needed for full functioning of the RCBO but isn't a protective earth.

 

[felix]

Thanks Plugwash. That makes perfect sense.

 

[bornagainsparkie]

Thanks Felix & Plugwash

Appreciate both your responses and it does confirm what I was thinking but reassuring to have good 2nd opinions, I will confidently take the plunge and report back if I learn anything different.

Just goes to show though, we're never too old to learn and should never be afraid or embarrassed to ask!

Certainly be in touch if I have other queries on anything

Sincere thanks

 

[ban-all-sheds]

Sadly I think that some of us were too old to learn the day they were born....

 

[mapj1]

In those I have seen, the functional earth goes to transient suppression devices, it will still 'work' if it is left dangling, but may be more prone to nuiscence trip from certain types of load.
The 'test', at least on the ones I've cracked open, creates an imbalance by linking a 8.2K resistor between feedside Neutral and loadside Live (or the other way about.) The whole point is it then doesn't need a reliable earth connection to still work, which is important in some TT installs as they still offer protection to users of hedgeclippers falling into the pond, even with a flakey house earth rod (the rod might be almost open circuit before anyone notices ).
Many of the cheaper brands (volex for example) don't have these devices and then there is no FE connection at all.
Please give us time to read the post, man, before you start worrying! some of us are busy at the weekends .

 

[bornagainsparkie]

Comments noted with thanks!