Interested in your thoughts....

[Adam W]

434.2.1
"The part of the conductor between the point of reduction of CSA or other change and the position of the protective device shall... ... not exceed 3m in length..."

Does that help?

ie are you fusing it down after the SWA, or could you just use, say, a 4mm radial throughout?

 

[Richard Burns]

The definition in the BGB of a ring is a final circuit in the form of a ring with a single point of supply, and effectively this is what you have, the single point of supply being the end of the SWA.

Or perhaps if the ring is parallel cables running down the counter you could wire it as a radial circuit with two parallel conductors! though I hate to think of the problems that could cause later.

 

[Engineer54]

434.2.1
"The part of the conductor between the point of reduction of CSA or other change and the position of the protective device shall... ... not exceed 3m in length..."

Does that help?

ie are you fusing it down after the SWA, or could you just use, say, a 4mm radial throughout?

Are you being serious here, or is this another chicken joke?? lol!!

 

[Knobhead]

Could you not run two SWA’s to each of the JB’s and run it as a true ring from the point of origin?

 

[Deleted member 9648]

Could you not run two SWA’s to each of the JB’s and run it as a true ring from the point of origin?

Or two 4.0mm radials to the sockets from the SWA joints...still 32a circuits.

 

[mogga]

couldnt you fit mcb 1way modular box inplace of the Joint box hence making your swa a distribution circuit then the FRC from there? this would also provide isolation ??

Iv seen counters with their own 8way DBs mounted within the counter to assist with this and it also means that if providing a large enough db in counter you could have seperate radial circuits due to sockets being used and probably overloading the ring Once you add up a bainmarie microwave till equipment toaster griddle heat lamps at serve over coffee machine coke machine ect ect you will keech tourself at the possible loads and Diversity shouldnt realy comeinto it as the canteen staff just see a plug n use it regardless of what else is on

 

[Adam W]

Are you being serious here, or is this another chicken joke?? lol!!

No, and I still don't know what a "FRC" is in this context.

 

[Chr!s]

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!!

I see, providing the circuits meet the requirements of BS7671 i see no issues, its not standard but then we are allowed to design our own circuits.

 

[Richard Burns]

No, and I still don't know what a "FRC" is in this context.

The meaning here is Final Ring Circuit more formally Ring Final Circuit (RFC).

 

[Engineer54]

This Submittal came across my desk on Monday. Like some others here stated, there is nothing particually wrong electrically, but to my mind not really an acceptable layout on what is, a prestige project. So the initial submittal was rejected, on this and a number of other issues. The submittal was back on my desk yesterday morning, now showing 2 X 3core 4mm SWA to the JB box's and 2 X 3 core 4mm building cables forming the Final Ring Circuits, along with the other revisions that were requested...

I didn't mention in my OP, that the project specification calls for minimum size of 4mm conductors for power circuits, as that would have confused matters, and wasn't anything to do with why i asked for your thoughts on what is commonly known as a ''lollipop ring''. Personally, i would always want to see ring circuits starting and finishing at the protective device at the supplying DB/CU. If nothing else it would be a little confusing for an electrician at a latter date, to see a single cable connected to a protective device labeled as a ''Ring Circuit''

Anyway thanks all, for your thoughts. As i guessed there were the fores and against's, and none in this case being right or wrong, as in my case, more to do with personal preference as this arrangement will comply with BS 7671...

 

[Engineer54]

couldnt you fit mcb 1way modular box inplace of the Joint box hence making your swa a distribution circuit then the FRC from there? this would also provide isolation ??

Iv seen counters with their own 8way DBs mounted within the counter to assist with this and it also means that if providing a large enough db in counter you could have seperate radial circuits due to sockets being used and probably overloading the ring Once you add up a bainmarie microwave till equipment toaster griddle heat lamps at serve over coffee machine coke machine ect ect you will keech tourself at the possible loads and Diversity shouldnt realy comeinto it as the canteen staff just see a plug n use it regardless of what else is on

All the bigger floor standing and the bigger mobile stuff like the Brain Marie's, pukka espresso machines etc, are all supplied via dedicated floor outlets, similar to the Britmac floor outlets , some of which are 3 phase jobby's all on their own radial circuits... These ring circuits are for general loads on the service counter.

 

[Adam W]

The meaning here is Final Ring Circuit more formally Ring Final Circuit (RFC).

OIC.
... So that would be a Ring Final Circuit (RFC) as opposed to a Radial Final Circuit (RFC)?

 

[Big n Daft]

I'm still with the chicken on this chaps........................

 

[mogga]

sounds like its "Sorted"

 

[Engineer54]

No, and I still don't know what a "FRC" is in this context.

lol!! ...Enough said then!! Your problem, ...not mine!!