Mcb or rcbo ?

[devonsparky]

I always get different views on this one.

I'm wiring a shop (commercial premises) and have done the install in conduit and through p-clips above the ceiling tiles.

My understanding of the regs is that all TN systems must meet 0.4s disconnection times. (Table 41.1)

Any of you guys got any input on this one?

 

[Engineer54]

(C&G 2360/NVQ 3/C&G 2391)

I like the sound of that C&G 2360... lol!!!

 

[devonsparky]

ha ha .......... it makes you competant enough to be able to read to the pompous posts you read on here at times!!

 

[D Skelton]

ha ha ............... yeah fair point 'D Skelton'. I'm just a sparky who gets twisted and tied in knots sometimes and I guess I interpret the regs my way but listen to others who feed me different ideas/advice etc

But I respect your point as some questions do come across as 'green' from time to time but I like to hear different thoughts from people

I'm no different. I'm sure during my time on this forum I've asked a fair few basic questions and also had one or two blonde moments, hence why I'm not tearing into you with a "Call yourself an electrician but don't know the answer to
this!!!!" type response lol

To be fair, the requirements for RCD protection for socket outlets is easy info to find, and the fact that you mentioned those dreaded letters 'D' and 'I' hahaha, could lead some to assume the worst, however I didn't want to assume, that's why I asked. I meant it in the least condescending way possible, I promise

How do I know you have the background/qualifications etc to take your 'advice' ???? lol

You don't

Edit: apologies if my question came across as pompous.

 

[Jonny66]

Seems to me that as this (Spar shop) is a place of work then the employees (who will be using the sockets), must be instructed persons. The manager will have a duty of care to instruct them (or any employee) in the safe use of any electrical equipment. I believe this is a statutory requirement under the EAWR and H&S legislation.

As such IMO RCD additional protection is not required for the majority of the circuits the OP has installed. However, perhaps this should of been discussed with the client at the design stage.. for what its worth, I would install RCD protection only on the tea point/kitchen area sockets and those used by cleaners and label the sockets accordingly.

 

[Geoffsd]

Agreed!
However our ECA assessor says we can have loop impedances up to 1667 ohms as long as the circuit is 30mA protected.

Very worrying.

Was that all he said or were any (exceptional) circumstances also mentioned? e.g. TT.

 

[Engineer54]

However our ECA assessor says we can have loop impedances up to 1667 ohms as long as the circuit is 30mA protected.

And that's the problem, ...that statement is fine, if were talking about a fault developing on a circuit. It isn't all right when it is KNOWN that a circuits Zs doesn't meet ADS requirements. You are then almost in TT territory where your totally relying on a RCD for your earth fault protection. The same question can then be asked, ...So what happens when that circuit is protected by an RCD that isn't working correctly!!

 

[tigerpaul]

Yes that is exactly what he said, it's a TN-S system btw.

 

[nick611]

you do not need rcd protection on these sockets. you only need to provide an rcd socket for use by cleaner/workmen etc. the shop workers are skilled or supervised persons. and the fabric of the building will be worked on by skilled builders. this is stated in 7671 and the on site guide. disconnection will be achived by mcb,s

 

[needasparks]

if the staff of the shop are considered to be "skilled or instructed persons" then no need for RCD if the disconnection times are met by the MCBs. i do work in a few spar shops and none of them have RCDs.

Buying beer don't count as working there tel.

 

[Brightspark2]

you do not need rcd protection on these sockets. you only need to provide an rcd socket for use by cleaner/workmen etc. the shop workers are skilled or supervised persons. and the fabric of the building will be worked on by skilled builders. this is stated in 7671

I disagree I dont believe there classed as skilled or instructed persons as defined in BS7671...

I dont think nuisance tripping is an issue, how often does it actually happen?...

Sent from my Xperia S using next doors WIFI.

 

[bartkusal]

you do not need rcd protection on these sockets. you only need to provide an rcd socket for use by cleaner/workmen etc. the shop workers are skilled or supervised persons. and the fabric of the building will be worked on by skilled builders. this is stated in 7671 and the on site guide. disconnection will be achived by mcb,s

Disagree on this. you cant class a shop worker as skilled or supervised person. Skilled is electrician, supervised is supervised by skilled person, that is electrician. And then comes the resident engineer,if there is one you dont need rcd anywhere, but that has to be agreed on design stage of installation and well documented...
The

 

[bartkusal]

Skilled person - a person with technical knowledge or sufficient experience to enable him/her to avoid dangers which electricity may create.

 

[Jonny66]

you do not need rcd protection on these sockets. you only need to provide an rcd socket for use by cleaner/workmen etc. the shop workers are skilled or supervised persons. and the fabric of the building will be worked on by skilled builders. this is stated in 7671 and the on site guide. disconnection will be achieved by mcb,s

Totally agree with the above, see post 19....

Disagree on this. you cant class a shop worker as skilled or supervised person. Skilled is electrician, supervised is supervised by skilled person, that is electrician. And then comes the resident engineer,if there is one you dont need rcd anywhere, but that has to be agreed on design stage of installation and well documented...
The

You can disagree all you like and try to interpret who is and who isn't skilled or supervised or instructed....but your wasting your time.:banghead:
It is a Statutory LAW (EAWR and H&S Legislation) that Employers have a duty of care to provide training and supervision/instruction to their Employees along with risk assessments which may include prohibiting the use of personal equipment in socket outlets etc etc......therefore the Spar employees must be Instructed Persons By Law and as such RCD protection is not required as stated in BS7671 which by the way is non-statutory. Any sockets used by ordinary persons will be a different matter.....:wink_smile:

 

[D Skelton]

You can disagree all you like and try to interpret who is and who isn't skilled or supervised or instructed....but your wasting your time.:banghead:
It is a Statutory LAW (EAWR and H&S Legislation) that Employers have a duty of care to provide training and supervision/instruction to their Employees along with risk assessments which may include prohibiting the use of personal equipment in socket outlets etc etc......therefore the Spar employees must be Instructed Persons By Law and as such RCD protection is not required as stated in BS7671 which by the way is non-statutory. Any sockets used by ordinary persons will be a different matter.....:wink_smile:

Then by your argument, every employee in every shop, office, school, library, police station etc..... every employee in every business or establishment where there are sockets that exist without RCD protection is an instructed person. IMHO, that is not the case. No matter how much training is given to a shelf stacker on how to use a non RCD protected socket outlet, it still doesn't make them an instructed person.

BS7671 defines an instructed person as "A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create."

My interpretation of this would be permanently employed maintenance staff in large commercial or industrial premesis. Not electricians but have enough knowledge to know how to complete simple electrical tasks and know what is involved with more complicated electrical tasks that electricians would carry out. Also, over the years thay would have worked alongside numurous electricians and at least been passed some technical knowhow, but just not enough to make them skilled.

I guess at the end of the day, how this particular description is interpreted is down to the individual. In which case, there's no point getting irate about another persons interpretation because all we can have on this matter is an opinion. There are no facts to go by.

 

[Jonny66]

Then by your argument, every employee in every shop, office, school, library, police station etc..... every employee in every business or establishment where there are sockets that exist without RCD protection is an instructed person. IMHO, that is not the case. No matter how much training is given to a shelf stacker on how to use a non RCD protected socket outlet, it still doesn't make them an instructed person.

It's not my argument, the interpretation of an "Instructed Person" is written in statute law. And yes, you could say that every employee should be an instructed person,instructed by the duty holder, who has a duty of care to (as stated in BS7671) "adequately advise or supervise to avoid dangers which electricity may create" e.g the safe use of sockets and no personal equipment to be used etc....EAWR 1989.
It is the law, it dosnt need to be interpreted, it is there as statutory law.

However, it is open to opinion on whether to use RCD protection, and perhaps a risk assessment may suggest this is necessary.....
By the way, I wasn't getting irate, just fancied some debate, am I allowed to do that or am I being arrogant and stuck up??