De-rating a ring circuit

[tedjrr]

I've always been wary of 32A protection on ring ccts, perhaps not even logically... The ring itself probably has more outlets than is allowed on a ring but has a very low load. I have tripped a 6A breaker with a short-circuiting bulb, this was quite a bang. So, I'd hate to experience a dead short in a 32A circuit fault. I know that the fault currents are much greater than the rating of the cct, and that an overload must be many times the rating to trip a breaker. But' even so... 32A seems excessive fro a domestic environment...

 

[DPG]

I've always been wary of 32A protection on ring ccts, perhaps not even logically... The ring itself probably has more outlets than is allowed on a ring but has a very low load. I have tripped a 6A breaker with a short-circuiting bulb, this was quite a bang. So, I'd hate to experience a dead short in a 32A circuit fault. I know that the fault currents are much greater than the rating of the cct, and that an overload must be many times the rating to trip a breaker. But' even so... 32A seems excessive fro a domestic environment...

The number of sockets is not really that important. That just gives you flexibility of where you can plug your stuff in. You don't buy more electrical items just because there are more sockets available in the house.

 

[MJPD29]

Be wary or anything you see on this man's YouTube channel. Some things he does are questionable and his electric knowledge is basic and limited to kitchens and bathrooms. As for your ring circuit, if installed correctly there is no need to be wary of it installed on a 32a ocpd as this is exactly what it was designed to be installed with and is perfectly safe. No need to mess with something that works.

 

[pc1966]

I've always been wary of 32A protection on ring ccts, perhaps not even logically...

For its designed purpose (plenty of sockets over a whole flat/floor) it is perfectly fine. And in 70 years of use the practical experience is it works very well.

I have tripped a 6A breaker with a short-circuiting bulb, this was quite a bang. So, I'd hate to experience a dead short in a 32A circuit fault. I know that the fault currents are much greater than the rating of the cct, and that an overload must be many times the rating to trip a breaker. But' even so... 32A seems excessive fro a domestic environment...

For MCB and related RCBO the size of the "bang" is determined by the protection's let-through energy and at high currents is not so sensitive to the rating, with a 50A MCB letting though only about 3-4 times the fault energy of a 6A MCB.

Shorting out the supply MCB for sockets is not so common, often folks drilling/nailing a wall with a buried cable. More common I think is crushing a flex, and in the UK at least they have a 3-13A fuse which is much better at limiting fault energy than MCBs typically are.

For example, the worst-case spec for a BS1362 13A fuse at 300A fault is 0.01s so 900 A2s let-through and that is getting to the plateau of limiting (constant I2t) for the fuse so it will be much the same even if the prospective fault current is up in the 2kA region, where as for a 32A MCB the let-through there is around 8,000 A2s so almost ten times more, and a 6A MCB is around 4,000 so over 4 times more than a fuse!

 

[Risteard]

Be wary or anything you see on this man's YouTube channel. Some things he does are questionable and his electric knowledge is basic and limited to kitchens and bathrooms. As for your ring circuit, if installed correctly there is no need to be wary of it installed on a 32a ocpd as this is exactly what it was designed to be installed with and is perfectly safe. No need to mess with something that works.

I'd second that. He's a very silly boy (for want of using terms I'd prefer to describe him).