03-09-2015, 04:37 PM
(This post was last modified: 03-09-2015, 04:39 PM by ppppenguin.)
In the UK they are called RCD, RCCD or sometimes the older term ELCB (Earth leakage circuit breaker). In the US GFI/GFCI is the same thing. There are also voltage operated ELCBs which are very different beasts and totally obsolete for domestic and ordinary commercial use.
The mains voltage has nothing to do with the trip current. 30mA is useful for many purposes. 10mA is the most sensitive usually available in the UK and is good for protecting against shock in high risk areas. They are also a pain in the neck due to spurious trips. I've not heard of a 6mA RCD.
100mA and 300mA RCDs are sometimes used for protecting large installations. These often have a time delay before they trip because there is no inherent discrimination with RCDs. If you have a 30mA RCD and a 100mA RCD cascaded and you get a 100mA fault then either or both could trip. This is unlike fuses and MCBs where the lower rated device will normally trip on a fault if the system is designed correctly.
The mains voltage has nothing to do with the trip current. 30mA is useful for many purposes. 10mA is the most sensitive usually available in the UK and is good for protecting against shock in high risk areas. They are also a pain in the neck due to spurious trips. I've not heard of a 6mA RCD.
100mA and 300mA RCDs are sometimes used for protecting large installations. These often have a time delay before they trip because there is no inherent discrimination with RCDs. If you have a 30mA RCD and a 100mA RCD cascaded and you get a 100mA fault then either or both could trip. This is unlike fuses and MCBs where the lower rated device will normally trip on a fault if the system is designed correctly.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
