30A JB's and 32A ring final circuits

[SplitJugular]

ive been having a dispute with another electrician about using 30A JB's on rings

a ring is made up of 2 legs of 2.5mm T+E,
2.5mm T+E ref method C has current carrying capacity of 27A

now surely the JB has to be rated higher than the cable, but using a 30A jb although this is less than the 32A MCB its only joining one half of the circuit and is still higher than the rating of the cable
the arguement is that he thinks i should be using 45A JB's as they are rated above the MCB

whats peoples feeling on this matter as this is the first electrician ive met in 10 years that ever had a problem joining a ring with 30A JB's

i also did a little reasearch and although i couldnt find the correct reference in the regs book wikipedia stated that the cable size in a ring should be rated at no less than 2/3 ( two thirds) of the MCB
meaning that the cable rating has to at least be 21.333A so a 30A jb would be sufficient by 8.66A

a also if 30A JB's were not sufficient why do wholesalers not stock a 32A jb?

 

[telectrix]

you're right. your mate's wrong. sorted.

 

[Flanders]

Your right the 32 amp is shared over the to legs of the RFC

 

[Octopus]

out of interest where were you putting the JB? under the floor?

 

[SplitJugular]

yeh thought as much, this is what the NIC man had apparently told him on the inspection visit last friday, am i right in saying that during an NIC visit they may say something like this to challenge your knowlege of the regs and this would be an invitation to discuss whats right and wrong, being that the regs are not a statutory document and in a sense they are just theory, surely arguing this would prove to the NIC man that i have sound reasoning behind my work,

ive heard from other collegues that they were asked why back boxes were not earthed (apparently this has been dropped in the regs)
"why are back boxes not earthed?"
"because they dont have to be"
"what about when the face plate is taken off the box is then not earthed!
"you shouldnt work on an installation whilst it is live"

the last line my friend said apparently seemed to be the answer the NIC man was looking for

 

[SplitJugular]

Murdoch, this wasnt really part of the issue he's saying it as a general rule no matter where the jb is put on the circuit, and the whole accesible area is a very grey area, as im more than confident pulling up a fitted carpet and re-instating it, thus this would make a joint under the floor boards, and carpet an accesible area for me. inaccessable to me means out of reach even with access equipment or out of possible sight

 

[kingeri]

Murdoch, this wasnt really part of the issue he's saying it as a general rule no matter where the jb is put on the circuit, and the whole accesible area is a very grey area, as im more than confident pulling up a fitted carpet and re-instating it, thus this would make a joint under the floor boards, and carpet an accesible area for me. inaccessable to me means out of reach even with access equipment or out of possible sight

I totally disagree with that. Okay, you can interpret certain elements of the regs this way or that, but I would say that accessible means you don't have to rip up carpets and boards to get to it!

 

[Tiny Spark]

yeh thought as much, this is what the NIC man had apparently told him on the inspection visit last friday, am i right in saying that during an NIC visit they may say something like this to challenge your knowlege of the regs and this would be an invitation to discuss whats right and wrong, being that the regs are not a statutory document and in a sense they are just theory, surely arguing this would prove to the NIC man that i have sound reasoning behind my work,

ive heard from other collegues that they were asked why back boxes were not earthed (apparently this has been dropped in the regs)
"why are back boxes not earthed?"
"because they dont have to be"
"what about when the face plate is taken off the box is then not earthed!
"you shouldnt work on an installation whilst it is live"

the last line my friend said apparently seemed to be the answer the NIC man was looking for

He would be buggered if he checked my work then, I still earth my back boxes LOL
I just consider it good practice and for the amount of time it takes I dont see why not even though it does not need to be done anymore.

As for the 30A JB thing, well thats the first time ive heard of that one....

 

[SplitJugular]

I totally disagree with that. Okay, you can interpret certain elements of the regs this way or that, but I would say that accessible means you don't have to rip up carpets and boards to get to it!

either way Murdoch its off topic and not the answer i was looking for, ive been on many different forums today and all of them have the same thread about 'accesible area' and no one agrees, look at it this way if i put a JB in a cupboard under the stairs that was small ish but big enough for me to get into (lets not flatter myself i am 14 Stone) but then my workmate sparkey who is 22 stone cant fit in cus he's too fat, is that jb now inaccessible? access depends on personal skill and commitment,

to say a fitted carpet is denying access would be the same as saying that light switches that were painted/silliconed in were inacessible because the customer wouldnt want the walls ruined aswell as the carpet??

 

[7029 dave]

30amp jb no problem what so ever

 

[SplitJugular]

He would be buggered if he checked my work then, I still earth my back boxes LOL
I just consider it good practice and for the amount of time it takes I dont see why not even though it does not need to be done anymore.

As for the 30A JB thing, well thats the first time ive heard of that one....

yup im with you i would do it as good practice but curious as to weather this is something the NIC do (give testing questions) i see why its a good thing and is a good indication of weather or not someone is just chancing it, i really want to know because im going for NIC registration soon and dont know if ill end up aruing my way off the NIC list

 

[Farmelectrics]

Don't use jbs row over lol

 

[SplitJugular]

Don't use jbs row over lol

not an option unfortunatly, i would if i had my way join with crimps in a box all the time, but this guy has for some reason got something against crimps and complains any time he see's them
(he gives me the work but it is council work and i see it as a waste of my council tax some of the lengths he goes to)

 

[Risteard]

And what about a 20A junction box? The Wiring Regulations only require that the current-carrying-capacity of the live conductors in a ring final circuit is at least 20A. Although I use 30A as it is easier worked with and prevents others giving off about you lol

 

[Octopus]

either way Murdoch its off topic and not the answer i was looking for, ive been on many different forums today and all of them have the same thread about 'accesible area' and no one agrees, look at it this way if i put a JB in a cupboard under the stairs that was small ish but big enough for me to get into (lets not flatter myself i am 14 Stone) but then my workmate sparkey who is 22 stone cant fit in cus he's too fat, is that jb now inaccessible? access depends on personal skill and commitment,

to say a fitted carpet is denying access would be the same as saying that light switches that were painted/silliconed in were inacessible because the customer wouldnt want the walls ruined aswell as the carpet??

But in your example you were saying under the floor boards, under the carpet - which is INACCESSIBLE.

Accessible is within reach without having to lift a floor board or moving a 120KG American Fridge Freezer