are most 80-100a CU rcd's. rcd's or rcbo's?
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ianmacd
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You mean RCCD? Are you sure its tripping due to current and not another reason like termal effects? They are rated in the same way a JB or light switch is in that it won't protect from over current but has only been designed to work up to that maximum current.
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green-hornet
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My signiture
Gents.
Gents.
Hi,
I might be wrong, but this is how I see it:
If you have a 30mA RCD protecting, say, 5 circuits, and under normal operating conditions these circuits draw 20A.
If you have a combined earth leakage of 15mA, this wouldn't be a problem.
If the combined load then increased to 40A, then the amount of current flowing down the earth path would increase in proportion (30mA) and trip the RCD.
So, although there's no overload protection, it could still trip under excessive loads.
The only way to solve it would be to get rid of as much of the leakage as possible.
Or have I got this wrong?
I might be wrong, but this is how I see it:
If you have a 30mA RCD protecting, say, 5 circuits, and under normal operating conditions these circuits draw 20A.
If you have a combined earth leakage of 15mA, this wouldn't be a problem.
If the combined load then increased to 40A, then the amount of current flowing down the earth path would increase in proportion (30mA) and trip the RCD.
So, although there's no overload protection, it could still trip under excessive loads.
The only way to solve it would be to get rid of as much of the leakage as possible.
Or have I got this wrong?
Earth faults (L-E or N-E) have nothing to do with the load attached to the circuit..
OK.
The RCD variant known as an RCCD; which we commonly call "an RCD", will provide earth leakage protection, yet has NO capability for overcurrent protection. (I have seen one installed on a shower supply, henley`d straight off the tails, into a 2 module enclosure containing a 63A/30mA RCD. That circuit has NO overcurrent protection whatsoever.
The RCD variant known as an RCBo, which we commonly call "an RCBo", provides overcurrent protection, and earth leakage protection.
HTH
KME
The RCD variant known as an RCCD; which we commonly call "an RCD", will provide earth leakage protection, yet has NO capability for overcurrent protection. (I have seen one installed on a shower supply, henley`d straight off the tails, into a 2 module enclosure containing a 63A/30mA RCD. That circuit has NO overcurrent protection whatsoever.
The RCD variant known as an RCBo, which we commonly call "an RCBo", provides overcurrent protection, and earth leakage protection.
HTH
KME
Normal circuit theory says they must have.
Current in a series circuit remains constant throughout.
If you introduce a N - E fault, you are introducing a parallel path back.
Current in a parallel circuit will split down each leg of the parallel path in proportion to the resistance of each leg.
If the resistance of the two paths remains the same, and you increase the current (the load), then it stands to reason that the current down each parallel return will increase.
So, circuit current - 10 A.........N - E leakage 15 mA
circuit current - 20 A.........N - E leakage 30mA
thats wrong ads
the leak will only draw what ever current is drawn due to its resistance value
regardless of the load.
i.e a lighting circuit that has 10 lighting points but only 1 is switched on and the leakage is 10ma turn the other 9 on and the leakage will be the same as long as no other leaks are connected with the other 9
Sorry in this case it doesn't work like that..
The load that you are changing is in parallel with the fault.
If you had parallel resistances and then a series load then the current would change, but an earth fault uses different return path...
You need to draw it out then you will see..
The load that you are changing is in parallel with the fault.
If you had parallel resistances and then a series load then the current would change, but an earth fault uses different return path...
You need to draw it out then you will see..
Where's this leakage come from? That has nothing to do with the overload characteristics of an RCD, of which there are none. If you have a leakage the RCD operates as it is doing it's job of protecting against leakage to earth. If there are no faults there is no leakage, ergo it doesn;t trip, and just melts.
