Interested in your thoughts....

[Engineer54]

Here's one for you... I've been going through submittal drawings for a staff canteen, i won't go into too much detail but the means of access to the service counter is via below a modular tiled raised floor system from the DB.

The part of the submittal that i'm going to refer to, is the two ring circuits for the power outlets on the service counter to supply the various hot and cold drinks, food heating and cooling appliances etc.
They are proposing a 3 core 6mm SWA to a wall JB and a FRC within counter stud construction to a surface mounted dado type PVC trunking system housing the socket outlets etc wired in 2.5mm 3 core building cable, connected to the SWA via that wall JB. The use of the SWA is to conform to the project specification of only mechanically protected cables being allowed below raised floor areas.

So what are the thoughts on this arrangement, i'd be interested to know what others may think here??

 

[Guest123]

Are you working to BS 7671 mate???

 

[Deleted member 9648]

I have come across this sort of arrangement before...the only issue I can see is the possible future difficulty in carrying out RFC tests,as the point where the radial becomes a ring may not be easily accessible for splitting and testing. Beyond that I cant see a problem. That said a 4.0mm 30a radial would possibly be a better solution.

 

[Engineer54]

Are you working to BS 7671 mate???

Another bone of contention Lenny!! Yes and No ...lol!! BS 7671 is one of the approved standards in the contract specifications. But basically calls for the highest international standards.. Something that i have to nail down without prejudice to the contractors!!

 

[Guest123]

Only reason I ask is the description of a ring final circuit in app 15........"A ring final circuit starts and finishes at the distribution board"

Take that as you will.:stooge_curly:

 

[Engineer54]

Only reason I ask is the description of a ring final circuit in app 15........"A ring final circuit starts and finishes at the distribution board"

Take that as you will.:stooge_curly:

My thoughts exactly ...lol!!!

 

[Adam W]

Sorry, what's an 'FRC'?

'Free Range Chicken'?

 

[Chr!s]

What size fuse is protecting, the swa and frc?

 

[Engineer54]

What size fuse is protecting, the swa and frc?

Standard B32A RCBO....

 

[Chr!s]

Standard B32A RCBO....

So a single 32 amp protecting the SWA and the two ring circuits? cant see know issues other assessing loads.

 

[Engineer54]

So a single 32 amp protecting the SWA and the two ring circuits? cant see know issues other assessing loads.

Sorry, some confusion here...lol!! No a single 6mm SWA with it's own RCBO, feeds each FRC via separate flush wall connection/JB box with DIN rail connectors... Hope that clears up any confusion in my OP. ..lol!!

 

[Chr!s]

Lol, i'm non the wiser now.

So A 32 amp RCBO protecting the SWA, which feeds the JB Box, there two ring circuits are connected, will there be any protection provided for the ring circuits at the JB Box or are they reliant upon the 32 RCBO which also protects the SWA? Lol

 

[Engineer54]

Lol, i'm non the wiser now.

So A 32 amp RCBO protecting the SWA, which feeds the JB Box, there two ring circuits are connected, will there be any protection provided for the ring circuits at the JB Box or are they reliant upon the 32 RCBO which also protects the SWA? Lol

2 SWA Circuits, each protected by an RCBO, each going to it's own JB box, each supplying a FRC. Each FRC supplying half the service counter. It's a fairly long counter with an extensive amount of various appliances as described in the OP. Any clearer now ?? lol!!

 

[netblindpaul]

Ahh the ubiquitous "lollipop circuit".

I have my opinions, but I'll wait for now...

 

[Des 56]

Appendix 15 refers to a ring starting and ending at the dist board,but it also says for domestic and simmillar premises, so maybe app 15 may not be appropriate for refering too in this case


433.1.1 (ii) brb
The rated current or setting of the protective device does not exceed the lowest of the current carrying capacities of any of the conductors of the circuit

Its not a standard circuit as we know it but it complies with the above,