Why not 2 x 16A MCB's on a ring?

[ericmark]

I know it will not work with RCBO's and it would use two slots instead of one. But a few have talked about radials instead of rings because with a ring high load either end can cause an overload without tripping the 32A MCB.

Fit instead two 16A MCB's and most of the objections to rings vanish. Should the ring be loaded heavy one side or even broken in error the MCB would still ensure automatic disconnection with an overload, yet still give one most of the advantage of a ring final.

As to if the two 16A MCB's should be linked not sure? Also not sure if two 20A MCB's could be used to give a 40A ring final?

So why don't we do it? I must be missing something but what?

 

[bernardgreen]

Simpler and probably less expensive to construct the ring with cable that can carry 32 amps for the time it takes for the MCB's thermal trip to operate.

Or make the ends of the ring out of 32 amp cable and the middle section out of lower amperage cable.

Of course there is a problem if one end of the ring goes open circuit and all the load then passes along the other leg to the MCB

 

[PBC_1966]

I really can't see any major changes such as this being made to the British ring circuit. I see it most likely staying in its present form unless and until it's abandoned completely in favor of radials.

 

[JohnW2]

Simpler and probably less expensive to construct the ring with cable that can carry 32 amps for the time it takes for the MCB's thermal trip to operate.

... but there would then be no point in having a ring. Other than CPC redundancy, just about the only other advantage of a ring final is that (given the regs) it allows one to use a cable which is not rated to carry the current that the OPD will allow to pass.

Kind Regards, John

 

[JohnW2]

I really can't see any major changes such as this being made to the British ring circuit. I see it most likely staying in its present form unless and until it's abandoned completely in favor of radials.

Agreed.

Kind Regards, John