ringmain

[MartinSigsworth]

I keep hearing the reason why ringmains are dangeous is because if there is a loose connection or a break you'll pull twice the current at the break

I have never heard of this and think there totally talking out there buttholes

Can you confirm that they are

 

[Guitarist]

Do you mean that you have never heard of what happens when a ring final circuit is broken?

 

[MartinSigsworth]

How can you pull twice the current on the circuit at the break it'd pop the breaker or fuse

 

[Richard Burns]

On a ring main you have two conductors in parallel each carrying (approximately) half the current that is drawn by the circuit. If you break the ring then all the current will be carried by only one conductor. This can be considered as drawing twice the current but it is better to say that the total current is now carried by one conductor. This could well overload the current carrying capacity of that conductor since it is not designed for that loading.

 

[rich.250]

As Richard burns said.
Basically like a radial on double the correct breaker rating.
Ie 2.5mm radial on a 32a

 

[Deleted member 26818]

It's not so much that conductors will have to carry the full current, which might not actually be any more than they would carry in normall use.
It's more to do with the fact, that the break would not be noticed, whereas with a radial it would

 

[Snapester]

2.5mm cable is only rated at around 20amps so if the ring final is broken then in effect the ring has become two radial circuits in which the circuit protective device is rated at 32AMPS and as the cable is only rated around 20AMPS there is a possibility that the cable could potentially become over loaded and become damaged before the MCB would trip.
This is why it is dangerous if the ring is broken.