elcb and borehole pump

just because something has been working for years does not always mean it is fault free.

Just because something is brand  new, does not always mean it is fault free either.


If it was me, I'd be trying to separate effects due to the pump from effects due to the rest of the wiring.


1) I presume it is actually an RCD - not an earth leakage circuit breaker (an RCD looks at the difference of neutral and live current, and tripe if the mis-match is too  great.  An earth leakage circuit  breaker measures current in the earth wire, and trips if it is too great.)

Since about 1980 RCDs have been preferred ,as they can also detect current leaking to earth via paths other than the green and  yellow wire, perhaps through people and wet feet to ground)  If it is an ELCB, then it should be replaced. I bet it is not.


And be sure it is an RCD that is tripping, and not an MCB (that would be an overload matter)



2) So, is there a problem with the rest of the wiring , or the new pump ?

How is the pump controller wired and how is it earthed. Also, what do the maker's instructions recommend. I imagine it will say to supply it via a normal 30mA RCD is OK, but it would be good to confirm that point, and they do not recommend something else.

Can you run the pump, and just the pump, via the offending trip? You need to be able to completely isolate every thing else on the same supply to do this test.


How is the main earth organised (TT, TNS, TNC-s ) , and if TT, where is the electrode in relation to the borehole?


If it runs OK in isolation, then we need to look at the rest of the installation. If not we need to look harder at the pump and it's wiring.


Can you verify there is no neutral to earth fault in the rest of the installation (and if there is an N-E fault, note that flicking off single pole breakers is not enough t for this test as it does not disconnect either N or E - they only break the live. )


Can you measure the residual current (LN imbalance) and is this high enough for concern ? About 30% is the threshold - so any more  than 10mA L-N difference on a circuit protected by a 30mA RCD would be cause for some sucking of air between the teeth.

just because something has been working for years does not always mean it is fault free.

Just because something is brand  new, does not always mean it is fault free either.


If it was me, I'd be trying to separate effects due to the pump from effects due to the rest of the wiring.


1) I presume it is actually an RCD - not an earth leakage circuit breaker (an RCD looks at the difference of neutral and live current, and tripe if the mis-match is too  great.  An earth leakage circuit  breaker measures current in the earth wire, and trips if it is too great.)

Since about 1980 RCDs have been preferred ,as they can also detect current leaking to earth via paths other than the green and  yellow wire, perhaps through people and wet feet to ground)  If it is an ELCB, then it should be replaced. I bet it is not.


And be sure it is an RCD that is tripping, and not an MCB (that would be an overload matter)



2) So, is there a problem with the rest of the wiring , or the new pump ?

How is the pump controller wired and how is it earthed. Also, what do the maker's instructions recommend. I imagine it will say to supply it via a normal 30mA RCD is OK, but it would be good to confirm that point, and they do not recommend something else.

Can you run the pump, and just the pump, via the offending trip? You need to be able to completely isolate every thing else on the same supply to do this test.


How is the main earth organised (TT, TNS, TNC-s ) , and if TT, where is the electrode in relation to the borehole?


If it runs OK in isolation, then we need to look at the rest of the installation. If not we need to look harder at the pump and it's wiring.


Can you verify there is no neutral to earth fault in the rest of the installation (and if there is an N-E fault, note that flicking off single pole breakers is not enough t for this test as it does not disconnect either N or E - they only break the live. )


Can you measure the residual current (LN imbalance) and is this high enough for concern ? About 30% is the threshold - so any more  than 10mA L-N difference on a circuit protected by a 30mA RCD would be cause for some sucking of air between the teeth.