Earth leakage question.

[Dairyspark]

Hi again,

So back at the bank again today and I have another question for you all. Recently bought myself a Earth leakage clamp meter and decided to try it out today, imagine my shock and horror as I clamp the tails of one DB and find 4.2A of leakage apparently. So I switch off the board and it drops to 12mA. I then switch it back on and back to 4A it goes and when I switch off the other DB it drops down again. So when both boards are on it’s at 4A but when either board is off, individual DB’s are between 10-12mA….does that make sense and if yes can anyone explain why?

 

[Geoff1946]

Sounds to me like a load is wired phase to one board, neutral to the other.

 

[steptoe]

How exactly are you measuring it,?
On the earth itself, or across the tails,?

 

[Dairyspark]

Across the tails…..is this where you tell me I’ve done it wrong?

 

[Dairyspark]

Sounds to me like a load is wired phase to one board, neutral to the other.

This could potentially be possible, as there is a newer board been fitted to supply lighting and then the original power and lighting board.

 

[Mike P]

Are you measuring across live and neutral phases and leaving main earth out of clamp meter jaws?

 

[Dairyspark]

Yeah, I’m clamping round Line and Neutral together.

 

[Geoff1946]

Just switch on both boards, watch the 4amp, "unbalance" on your meter, and then switch off each MCB in turn. When the mystery current disappears that's the offending circuit with mis-wired neutral. Must be something fairly significant; it's about 1 kW.

Afterthought; It could be more than one.

 

[Dairyspark]

So, issue is across 3 lighting circuits it’s all wired in singles…yay!

 

[Sidewinder]

Don’t forget about the possibility for diverted current too.

 

[Dairyspark]

Don’t forget about the possibility for diverted current too.

Oooo do explain?

 

[Sidewinder]

Current which has its origins outside the installation, typically from N or E and then manifested in the installation.