BS 7671 Section 521.8.3

Not being familiar with all the BS numbers I did an Internet search which threw up the Hager Guide to Junction Boxes, I have no read it yet but it might be a starting point.

https://www.hager.co.uk/files/download/0/2801_1/0/Guide_to_Junction_Boxes.pdf

The I think the simple answer is if it’s traditional junction box it needs to be fixed to something, accessible and the cables going into it need to be clipped, but if it’s a new style maintenance free box then those are not requirements.

Moesebnew: 
 

Section 521.8.3 of BS7671 states: Where two or more circuits are terminated in a single junction box this shall comply with BS EN 60670-22. My question is what if several circuits will terminate in a single wiring device back box which are usually  manufactured to comply with   BS EN 60670-1.

BS 7671 doesn't define “junction box”.

Given the definition of circuit, however, we might conclude that it must be possible to terminate two circuits into one accessory fitted to an accessory backbox not complying with BS EN 60670-22, otherwise it would be impossible to use a fused connection unit to supply a fused spur as shown in the diagrams of Appendix 15 of BS 7671.

Reasoning: There are strictly two circuits present … the incoming supply circuit, say 32 A ring final circuit or 20 A radial circuit, and the outgoing spur with lower cross-sectional area conductors. The spur must be a different circuit (as defined in Part 2 of BS 7671, because it is not protected by the same overcurrent by the same protective device as the supply circuit .

B.S. 7671's definition of a “circuit” is daft and illogical.

Z.

Zoomup: 
 

B.S. 7671's definition of a “circuit” is daft and illogical.

 

Z.

What's your reason for saying that?

I prefer the definition found in the 13th edition:

Circuit. “An arrangement of conductors for the purpose of carrying current”.

Starting  a new “circuit” at a protective device makes no sense. 

The current modern definition should be renamed.

Z.

Yes, I can see that.

I think BS 7671 has that definition, simply because of the scope of the standard mainly being aimed at protection against fire and shock … and the primary device for that traditionally [but now not always for electric shock] being the OCPD.

The difficulty with “circuit” to the 13th Ed definition, is that is what we now call the system (and so does the EAWR). We have a need to distinguish between the system as a whole, and the subdivisions that we currently term (rightly or wrongly) installations and circuits.

Starting  a new “circuit” at a protective device makes no sense. 

It's useful to have a word to distinguish points that are grouped together but somehow separate from other points - e.g. “the upstairs lighting circuit” or the “cooker circuit” or the “socket circuit” - usually the only difference is that they are connected to a different way in a DB or CU. If the protective device they're connected to isn't to be the distinguishing feature, then what would be?

I'd add that many if not all the characteristics of a “circuit” - required live conductor size, c.p.c. size, size of load it can supply, v.d., maximum cable length, disconnection time relate to the characteristics of the protective device - and so can differ quite substantially from those connected to a different protective device.

My only gripe is that the definition is limited to overcurrent protective devices - I'd probably prefer to include all protective devices - e.g. RCDs as well.

    - Andy.

The 14th Edition had no definition of the word “circuit”.

It did though have a definition for “Final sub-circuit."

It was, “An outgoing circuit connected to a distribution board and intended to supply electrical energy to current using apparatus, either directly or through socket outlets or fused spur boxes”. Spur box = fused connection unit.

So back then even though a circuit may be a ring and then a supply is provided through a 13 Amp fuse via a spur box,  the circuit is just singular, a circuit in the traditional sense from supply through load and back to the supply.

Z.

AJJewsbury: 
 

Starting  a new “circuit” at a protective device makes no sense. 

It's useful to have a word to distinguish points that are grouped together but somehow separate from other points - e.g. “the upstairs lighting circuit” or the “cooker circuit” or the “socket circuit” - usually the only difference is that they are connected to a different way in a DB or CU. If the protective device they're connected to isn't to be the distinguishing feature, then what would be?

I

Way 1 Cooker circuit.

Way 2 Ring final up.

Way 3 Ring final down.

Way 4 Water heater.

Way 5 Lights up.

Way 6 Lights down.

Way 7 Lights outside.

Way 8 Garage.

There are always “Ways”.

A Way = “Parts into which something divides or is divided.”

Z.