Yet another RCD question

[jamminuk]

Does an RCD need an earth to operate? I know it's additional protection and works on a balance between line and neutral but does it need earth to operate?

Thanks in advance

Ben

 

[telectrix]

there has to be a path to earth on the circiut for the imbabalance to occur, but the RCD itself does not need an earth.

 

[jamminuk]

i suppose unless it leaks elsewhere?

 

[telectrix]

wel. yes. either through the cpc of the circuit, through damp, through your body. any path to earth will do

 

[sparks_114]

No, an RCD does not need an earth to work, but as above, current has to "leak" out of the circuit(s) protected by the RCD for it to operate. This leakage current is at the most 30mA (0.030 amps) before the RCD trips, although a healthy RCD will trip well within that. To clarify further, leakage current is, for instance, someone accidentally (or otherwise) coming in contact with a live wire in which case some of the current will flow through such person down to the earth. The RCD will then pick up that not all current leaving the line conductor is returning in the neutral and will thence operate because of this imbalance. Hope this helps too, I tried to make it simple but not sure if I've succeeded! Cheers

 

[jamminuk]

No, an RCD does not need an earth to work, but as above, current has to "leak" out of the circuit(s) protected by the RCD for it to operate. This leakage current is at the most 30mA (0.030 amps) before the RCD trips, although a healthy RCD will trip well within that. To clarify further, leakage current is, for instance, someone accidentally (or otherwise) coming in contact with a live wire in which case some of the current will flow through such person down to the earth. The RCD will then pick up that not all current leaving the line conductor is returning in the neutral and will thence operate because of this imbalance. Hope this helps too, I tried to make it simple but not sure if I've succeeded! Cheers

Yes mate that has made it clear thanks to you and telectrix, most helpfull and thanks for taking the time to help out, owe you a beer or two!!

 

[sparks_114]

Yes mate that has made it clear thanks to you and telectrix, most helpfull and thanks for taking the time to help out, owe you a beer or two!!

LOL, no worries fella. Well as a Muslim I don't drink but your appreciation is well received. Cheers

 

[MarkieSparkie]

If the RCD is of the conventional mechanical mechanism and toroidal transformer construction, it does not require a functional earth for the device itself to operate, but its final circuit does require a CPC.
If on the other hand the RCD is of the all electronic construction (like most RCBOs), it will require a functional earth to provide a reference for the electronics to operate, plus its final circuit will require a CPC.

 

[ezzzekiel]

had this question myself many moons ago, tried testing the rcd with main earth disconected and it it still tripped under test so theoretically no an earth is not required but some form of earth path must exist for enough current to leak to create an imbalance.

 

[jamminuk]

LOL, no worries fella. Well as a Muslim I don't drink but your appreciation is well received. Cheers

Maybe a mango lassi then mate ;-)