rcd question

[mojo]

Hi all,
this is my 1st post and my first electrical job for a while.

I apologise if these questions are simple but i would rather sound stupid and be safe than be quite and dangerous.

I have recently been made redundant and took a course and updated to the 17th and part p(did a 3 yr appprentership 12 yrs ago but hav`t done any electical work since) as the course was only 3 days ( a joke) u can only take in so much, i hold my hands up i obviously lack on knowledge and experience which i hope is where you guys come in.(sorry if that was long winded)

Im doing an extension on a house with a new cu going in he extension being fed from the main cu off 40a with swa cable, there is 1 ring main and 3 lighting circuits(already there i just 2nd fixed them)
question is do all circuits have to be rcd protected now or can i put the sockets only on the protected side and the lighting on the mains side, also there are only 3 sockets on the ring can i use a 20a or does it have to be 32a as its a ring. all help greatly appreciated.

 

[Darkwood]

As your doing new circuits they will have to comply with 17th edition so if any lighting wires lie within 50mm of the surface of a wall for instance they will need rcd protection unless they are protected by a steel conduit or run in armouring which i doubt you have done, their is a new cable on the market which also complies but again im sure youve just used the standard cable.
Note! capping isnt classed as protection in this case.
20amp ring although not the norm is perfectly fine.

 

[ashdog]

Hi Mojo

All circuits as per 17th edition should be RCD protected

If it's a ring final circuit then I believe this should have a 32 A MCB protecting it

 

[mojo]

thanks darkwood appreciate it.

another question, next week i have a small job a guy wants me to add a light in his front room to come on with the existing light , as i am adding to the installation does it then need rcd protection if not already protected that is

 

[Darkwood]

Hi Mojo

All circuits as per 17th edition should be RCD protected

If it's a ring final circuit then I believe this should have a 32 A MCB protecting it

17th edition only requires rcd protection where cables run through building structure within 50mm of the surface without sufficient mechanical protection so if the lighting installation was fully wired in conduit or mini trunking then it wouldnt require rcd protection, as this method isnt normally done in domestic you tend to find all circuits need rcd coverThere is no regulation saying a ring must be 32a as long as your circuit meets requirements fitting a smaller circuit breaker isnt a problem it could only be debated if it was prone to nuisance tripping and in this case it shouldnt be an issue.

thanks darkwood appreciate it.

another question, next week i have a small job a guy wants me to add a light in his front room to come on with the existing light , as i am adding to the installation does it then need rcd protection if not already protected that is

Im not too strong on the domestic regs as i dont do domestic and this one im not too sure so i leave this one to one of our other valued members.

 

[Doomed]

thanks darkwood appreciate it.

another question, next week i have a small job a guy wants me to add a light in his front room to come on with the existing light , as i am adding to the installation does it then need rcd protection if not already protected that is

I believe that if you are altering an existing circuit in any way it needs to be brought up to the 17th standards, which in most domestic situations means that RCD's are needed.

 

[martspark]

I believe that if you are altering an existing circuit in any way it needs to be brought up to the 17th standards, which in most domestic situations means that RCD's are needed.

thats dead rite if you alter it then has to be up to 17eenth in all ways
and ring main can have 30a breaker and still complied
you need rcd protection for lites ccts if supplys bathroom aswell as 4 walls
ta

 

[mojo]

thanks guys.

another quick 1 if the extension i am doing is fully rcd protected do i need any bonding

 

[electricAl]

Hia Mojo. I`m sure your candour is appreciated & lends itself to others wanting to help. However, a little more info from yourself would be helpful to those trying to advise...

Reading thru i realised you don`t actually mention type or use of extension, whether circuits also supply bathroom (or even a kitchen) - i`d guess not, but guessing can sometimes be...interesting?

Without wanting to discourage you (& i applaud you for aquiring 2382) your questions make me wonder...they`re pretty basic one`s covered by 17th exam surely? I understand your Regs course was only for 3 days but it doesn`t stop you informing yourself off your own bat. No offence (really) but is half way thru the job the time to be asking forum members how to design/protect it? Sounds like further training would be really advantageous to you.

Also, do we assume the job is being signed off by BC - or are you reg` with Part P scheme? Doing a Part P course is not quite the same thing - if that is what you meant - not really sure what such a course would consist of but they`d surely make you aware of your responsibilities re: Building Regs & EAWR?
You also mentioned that you`re only doing 2nd fix - out of curiousity, whose doing the I&T & cert(s)

Anyway, so as to not be too negative...

As Darkwood said, 20A is ok for RFC - but why20A? Why not 32A or better still make it a radial & save a bit of copper?
Just for clarity, all Ring Final Circuits do not have to be as per A1, A2 nor A3 - they are the suggested `standard` circuits allowing installation with fewer calculations needed.

As succintly put by Doomed >>>
"if you are altering an existing circuit in any way it needs to be brought up to the 17th standards, which in most domestic situations means that RCD's are needed"

...most ccts in domestic end up requiring RCCB/RCBO protection due to one or more of the reasons already given above:

Cables concealed in walls @ less than 50mm from any surface - for cables run within the wall fabric (normally parallel with the wall) - but not usually those that pass thru it (perpendicular to the wall) There are many properties where there is no such `concealment` but it`s far more common for this to occur. Mechanical protection via conduit etc is not likely in dwellings, nor SWA - tho it`s use is increasing for good reason.

Also, for any unprotected cables within walls containing metal studding etc whether >50mm or `passing thru`

Ccts serving socket-outlets (a no brainer)

Ccts supplying a room with shower or bath (this often applies to lighting circuits even if rcd protection not required due to cable routing)

Hope that clarifies...



As for your last Q - re: bonding, again, use of rooms may be relevent, but as a general rule further bonding won`t be needed assuming Main Equipotential Bonding has been carried out.
For instance, if we`re talking radiators here, then as extraneous parts they should already have an effective bond back at service intakes.

Please don`t allow any of my comments discourage you from asking further questions - that isn`t my intention & after all, thats the whole point of a a great forum such as this.

 

[mojo]

Hia Mojo. I`m sure your candour is appreciated & lends itself to others wanting to help. However, a little more info from yourself would be helpful to those trying to advise...

Reading thru i realised you don`t actually mention type or use of extension, whether circuits also supply bathroom (or even a kitchen) - i`d guess not, but guessing can sometimes be...interesting?

Without wanting to discourage you (& i applaud you for aquiring 2382) your questions make me wonder...they`re pretty basic one`s covered by 17th exam surely? I understand your Regs course was only for 3 days but it doesn`t stop you informing yourself off your own bat. No offence (really) but is half way thru the job the time to be asking forum members how to design/protect it? Sounds like further training would be really advantageous to you.

Also, do we assume the job is being signed off by BC - or are you reg` with Part P scheme? Doing a Part P course is not quite the same thing - if that is what you meant - not really sure what such a course would consist of but they`d surely make you aware of your responsibilities re: Building Regs & EAWR?
You also mentioned that you`re only doing 2nd fix - out of curiousity, whose doing the I&T & cert(s)

Anyway, so as to not be too negative...

As Darkwood said, 20A is ok for RFC - but why20A? Why not 32A or better still make it a radial & save a bit of copper?
Just for clarity, all Ring Final Circuits do not have to be as per A1, A2 nor A3 - they are the suggested `standard` circuits allowing installation with fewer calculations needed.

As succintly put by Doomed >>>
"if you are altering an existing circuit in any way it needs to be brought up to the 17th standards, which in most domestic situations means that RCD's are needed"

...most ccts in domestic end up requiring RCCB/RCBO protection due to one or more of the reasons already given above:

Cables concealed in walls @ less than 50mm from any surface - for cables run within the wall fabric (normally parallel with the wall) - but not usually those that pass thru it (perpendicular to the wall) There are many properties where there is no such `concealment` but it`s far more common for this to occur. Mechanical protection via conduit etc is not likely in dwellings, nor SWA - tho it`s use is increasing for good reason.

Also, for any unprotected cables within walls containing metal studding etc whether >50mm or `passing thru`

Ccts serving socket-outlets (a no brainer)

Ccts supplying a room with shower or bath (this often applies to lighting circuits even if rcd protection not required due to cable routing)

Hope that clarifies...



As for your last Q - re: bonding, again, use of rooms may be relevent, but as a general rule further bonding won`t be needed assuming Main Equipotential Bonding has been carried out.
For instance, if we`re talking radiators here, then as extraneous parts they should already have an effective bond back at service intakes.

Please don`t allow any of my comments discourage you from asking further questions - that isn`t my intention & after all, thats the whole point of a a great forum such as this.

well you have dicouraged me from asking further questions and i thought the whole point of this forum was to ask for advice it was my first job and and i had to make sure it was right, when panic mode kicks in the simplest things become difficult, and reading your comments was not the confidence booster i needed, i went to that job feeling down but thankfully all went well. i joined this forum for advice so next time keep your critisism to yourself if i wanted to be critisised i would of asked the wife

 

[electricAl]

well you have dicouraged me from asking further questions and i thought the whole point of this forum was to ask for advice it was my first job and and i had to make sure it was right, when panic mode kicks in the simplest things become difficult, and reading your comments was not the confidence booster i needed, i went to that job feeling down but thankfully all went well. i joined this forum for advice so next time keep your critisism to yourself if i wanted to be critisised i would of asked the wife

Fair enough.
Please totally ignore all that i wrote & carry on regardless.
I expressed my thoughts/opinions - i have no way of knowing if a single other person on here would agree with them in any way - so lets assume no-one would & i`m out of step.
So you`re as free to ask away as anyone is.
Goodbye.

 

[pevvers]

another question, next week i have a small job a guy wants me to add a light in his front room to come on with the existing light , as i am adding to the installation does it then need rcd protection if not already protected that is

I disagree with what other people have said, if you are just adding an additional point to a circuit then it is not a must to bring it up to 17th edition, just note the deviation on the minor works cert.

Sorry, didn't get to the bitching, I just read up to the part I disagreed with and then posted my reply....

Then I got to the bitching, happy days, it's just like the other forum all over again!!

I think I might just start my own forum....

 

[immy]

Interesting stuff. Got a question in one house the landing light keeps going out and it leaves a burnt smell in the lamp holder (part which holds the bulb) and trips the MCB. I have replaced the lamp holder and it worked fine for 2 days but its now burnt out again!! Does anyone know what could be causing this? Thank you.

Immy.

 

[Risteard]

I disagree with what other people have said, if you are just adding an additional point to a circuit then it is not a must to bring it up to 17th edition, just note the deviation on the minor works cert.

The competent person signing the Minor Electrical Installation Works Certificate is responsible for the Design, Construction and Inspection and Testing of the modified circuit. Surely the Design, Construction and Inspection and Testing must therefore comply with the IEE Wiring Regulations.

 

[Davey101]

Going back to the original post, I note you are feeding the new CU with a 40amp mcb? Not 100%, but I dont know if you'd get satisfactory discrimination between a 40amp, and a 32 amp mcb. Not THAT important, but not ideal IMO.