RCD tripping??
- Thread starter kevin1234
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sorry secure, in answering the previous post , explaining that an rcd would only trip when there was a load applied to the circuit. neutral becomes active and a leakages to earth happens with a NE fault. I agree that the use of RCD's is causing inherent problems to be exposed and the use of dual RCD's is causing borrowed neutral posts.
an RCD will detect a line to earth fault, or a neutral to earth fault when the circuit is loaded. it will not detect a line to neutral fault "short" as an RCD only detects an imbalance between live conductors and a short between line and neutral is dealt with by the MCB
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I'm sure Lectrician wouldn't mind if I quoted him from another post:
if it is a n-e fault it chould be rectified regardless.
n-e fault will trip rcd when you have load on circuit or any other circuit fed via that rcd, but will not trip an mcb.
in TNCS - PME, it will not cause immediate danger, but should be sorted.
with TNS earthing, with increasing load, you will have diverted neutral currents using your earth (via the fault), the more load, the more current will flow through the fault, on a ring cct you have 2x1.5mm/sq earth to carry almost half the current!! and if the neutral broke somewhere, it would carry all the current!! - i have seen several burnt out lighting circuits!!!!!!!
From the link I posted:
How do the RCDs work?
According to the principle"what goes in must come out"(or, more technically, the sum of all the currents meeting in any point in a circuit must be zero, otherwise the circuit will be broken - the Node Law), the residual current device operates by continually comparing the current flow both in the Active(the "IN" part, the Supply) and Neutral(the "OUT" part, the Return) conductors of the electrical circuit. If the current flow becomes unbalanced(there are some leakages detected), it means that some of the current in the Active conductor is not returning back through the Neutral conductor and is leaking to the earth - this triggers the device, which automatically closes the circuit.
Most RCD's do not have an earth connection*, therefore cannot detect an imbalance between live conductors and earth. They detect only an imbalance between live & neutral.
*Those that do have it, have a functional earth for "loss of neutral" protection.
if it is a n-e fault it chould be rectified regardless.
n-e fault will trip rcd when you have load on circuit or any other circuit fed via that rcd, but will not trip an mcb.
in TNCS - PME, it will not cause immediate danger, but should be sorted.
with TNS earthing, with increasing load, you will have diverted neutral currents using your earth (via the fault), the more load, the more current will flow through the fault, on a ring cct you have 2x1.5mm/sq earth to carry almost half the current!! and if the neutral broke somewhere, it would carry all the current!! - i have seen several burnt out lighting circuits!!!!!!!
From the link I posted:
How do the RCDs work?
According to the principle"what goes in must come out"(or, more technically, the sum of all the currents meeting in any point in a circuit must be zero, otherwise the circuit will be broken - the Node Law), the residual current device operates by continually comparing the current flow both in the Active(the "IN" part, the Supply) and Neutral(the "OUT" part, the Return) conductors of the electrical circuit. If the current flow becomes unbalanced(there are some leakages detected), it means that some of the current in the Active conductor is not returning back through the Neutral conductor and is leaking to the earth - this triggers the device, which automatically closes the circuit.
Most RCD's do not have an earth connection*, therefore cannot detect an imbalance between live conductors and earth. They detect only an imbalance between live & neutral.
*Those that do have it, have a functional earth for "loss of neutral" protection.
from the direct and or insinuated "jist" of my post on this subject , secure, you have misqouted me. Pleae read back and digest. I was hoping to help the OP.
i did edit my post to be correct, but the omission of "earth and" is my mistake. Hope you all understand my error. see other posts. Typo.
don't you mean "inclusion of" not "omission of".. since you've removed the bit you added in error?
indeed coljack, but i i'm hopeful that you and all dont make a mountain out of a small "inlclusion" when the thrust of what i was saying was educatutional to the op 
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No offence, I wasn't meaning to have a go, just to try & make it clear to the OP.
And kindly leave your thrust out of it!
And kindly leave your thrust out of it!
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