Circuit design for new extension

[Octopus]

Just thought about how, when and why an RCD operates and realized what a stupid question I've just asked! :shame:

Better question... Anyone know of a (cheaper than £45) source of external RCD spurs?

If he's your Uncle isn't he going to be happy to pay a competent relative to install a quality solution?

 

[telectrix]

much easier to run SWA without RCD, then fit RCD and whatever over current devices in a garage board in the shed. alternatively, cut a box in adjacent to the socket carefully and fit RCD FCU there.

 

[skamuk]

much easier to run SWA without RCD, then fit RCD and whatever over current devices in a garage board in the shed. alternatively, cut a box in adjacent to the socket carefully and fit RCD FCU there.

But say for instance he damaged the SWA and the neutral comes in contact with cpc, if the rcd is after the SWA run surely it won't trip?

 

[telectrix]

that is true, but SWA does not require RCD protection in itself. the only protection required is for overcurrent and fault protection.

 

[skamuk]

Sorted. running swa to rcd spur (in shed), feeding unswitched FCU to feed lights, using 2 cores of the 4-core swa to run switch live for lights back at the house, same rcd spur also feeding single socket in shed.

Got it sussed i think. Cheers!

 

[skamuk]

Problem. Ran SWA from socket on ring in house, to rcd spur in shed, rcd spur feeding single socket and some low voltage decking lights via switched spur.. RCD spur trips when electricity is restored. My wiring is fine and everything works without the rcd present.. Could it be a problem in the house causing it to trip?

 

[Octopus]

Problem. Ran SWA from socket on ring in house, to rcd spur in shed, rcd spur feeding single socket and some low voltage decking lights via switched spur.. RCD spur trips when electricity is restored. My wiring is fine and everything works without the rcd present.. Could it be a problem in the house causing it to trip?

ha ha ha, come on then list the tests you have done.

 

[skamuk]

continuity between l-n l-cpc n-cpc. IR. No problems...

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Tests carried out on my wiring only

 

[skamuk]

The only thing I can think of is the wiring in the house has seen better days, if there was a fault in there somewhere would it trip, if there was a residual current in the cpc? I thought RCD would only detect problems on the outgoing side and not the supply intake?

 

[bigbaddave]

As in tested ok.. What you mean what exactly are you test results?

 

[bigbaddave]

Is this for real bud?? Are you registered with a dreaded scam and what electrical qualifications do you have if you dont mind me asking

 

[bigbaddave]

continuity between l-n l-cpc n-cpc. IR. No problems...

- - - Updated - - -

Tests carried out on my wiring only

Wait a minute.. You have continuity between l&CPC and N-CPC.... A rcd picks up on what type of fault???

 

[Octopus]

For everyone else: read post # 35

http://www.electriciansforums.net/e...gulations/74813-please-help-3.html#post746812

 

[rattlehead85]

The phrase 'a little knowledge is dangerous' springs to mind. Alarm bells are ringing if you don't understand the working principles of a residual current device!!

 

[skamuk]

I understand how a RCD works, it monitors the voltage between L-N and if there is an imbalance between the two. The only way there could be an imbalance between the two is if one of them are leaking to CPC am I correct? and an rcd also has a cable that monitors the cpc so maybe this is what is causing it to trip... I don't know for sure this is why i'm here.

I didn't mean I have continuity between L-N L-CPC N-CPC, I tested for it, and got high readings all round. Murdoch asked what tests I carried out not what results did I get.

I'm not a registered electrician, but am at college studying c&g 2365 l2 and have near enough completed this year. Whole reason I'm on here is to seek guidance and learn from people who do have knowledge and experience... otherwise what is the point in the forum? So everyone can boast about how qualified and experienced they are, and have a go at the ones who aren't??

Every time I ask a question on here I get mixed messages, some wanting to help, others just want to harass you about your qualifications. I do appreciate the help. If it wasn't half term this week I would ask at college.

 

[dan86]

I do appreciate the help. If it wasn't half term this week I would ask at college.

you appreciate the help, but given the choice, you'd rather ask elsewhere?!

 

[Brightspark2]

I understand how a RCD works, it monitors the voltage between L-N and if there is an imbalance between the two. The only way there could be an imbalance between the two is if one of them are leaking to CPC am I correct? and an rcd also has a cable that monitors the cpc so maybe this is what is causing it to trip... I don't know for sure this is why i'm here.

No an RCD monitors current not voltage and to answer your earlier a question the RCD spur will not pick up a fault within the house. We dont install an RCD to protect against a neutral to cpc fault within a cable, we install an RCD to give protection for people using the circuit. Hence the SWA alone not needing RCD protection.

Seems like it's wired wrong to me....

 

[Octopus]

Do you own a MFT?

 

[skamuk]

Sorry yes it measures current and a neutral to cpc fault is one that it detects as well as a line to cpc fault. If there are 3amps being drawn by a load from the line conductor then the neutral conductor should also be carrying 3amps, if it is not the device will trip.

Yes I own a Metrel 61557 MFT.

 

[Octopus]

Sorry yes it measures current and a neutral to cpc fault is one that it detects as well as a line to cpc fault. If there are 3amps being drawn by a load from the line conductor then the neutral conductor should also be carrying 3amps, if it is not the device will trip.

Yes I own a Metrel 61557 MFT.

In which case time to dust it off and use it again.