In a kitchen, correctly wired with dedicated outlets to appliances and the tableau protected, and checked regularly, with a 30mA trip and a good earth. All wiring in quality cable in conduit to French standards.
Dismantling a 13A Aga (that has been switched off at the tableau MCB for four yers..) the other day someone touched the main element and got a shock, but the 32mA trip remained in place. Alarmed by this, and using a multimeter from the element to to the cast iron frame, I had a reading of 230V (or maybe 220V, I cannot remember - but is was a high reading!)
Switched the Aga MCB on and immediately the Aga control box sprang into life and the element commenced to heat up. Switched off and Aga died, but checked again and a voltage reading existed betwixt element and cast iron frame…but as before, the Aga was to all intents and purposes, dead.
With the multimeter locked in place, I switched off each MCB in turn and discovered that only when the steam tap was switched off, was there a zero reading. Checked inside the tableau and no evidence of the two circuits - Aga and steam tap - being connected. All connections, including earth, good and tight.
My question therefore - how/why is the Aga picking up a voltage reading, yet the control box is dead, when the steam tap is on? How can it be stopped? (I should say that now the Aga is physically disconnected from the circuit wiring, but, using the NCV facility of the multimeter, I get a ‘voltage present’ beep from the circuit that goes when I switch off the steam tap MCB…)
The ‘shock’ was possibly induced voltage. However, it should not be measurable unless the Aga metalwork is not earthed properly. If it were earthed properly then any induced current would flow to earth.
The cables for the two circuits could well run together above the ceiling - I cannot see them. But leaving the tableau and coming down the wall behind the place, they seem separated.
I did not check inside the control box if any wires are reversed, and it is now under a ton of cast iron. And I cannot remember seeing any bonding wires to the metalwork, but again, difficult to check now. I certainly hope the thing was well earthed as it is one big hunk of iron that plenty of people have touched…
HOWEVER, with the Aga all dismantled awaiting a new home, the circuit that is left still has something there. As I said earlier, with its MCB switched off, my no contact voltage tester still beeps, UNTIL the steam tap MCB is switched off…
Looking at it closer, it is weird:
Aga MCB off and Steam tap MCB on = a positive beep on my NCV tester on the Aga circuit.
Aga MCB on and Steam tap MCB off = no beep on my NCV tester on the Steam tap circuit.
What I am saying is, that the peculiarity only manifests itself on the Aga circuit and not on the steam tap circuit. Is this possible?
I am replacing the Aga with a big double door fridge/freezer, and need the old Aga circuit for this. As nothing is tripping and no one has been electrocuted, dare I assume that this is just a peculiarity and continue as is..?
It your multimeter digital or analogue? Some of the digital ones pick up a stray induced voltage but no real current, analogue have a resistance so it tends not to hapen. Electric shocks can sometimes be the dischage of static electricity
I think you should disconnect both circuits at the board & then trace exactly which wire is which by shorting them at the appliance/use end & metering them out.
I reckon that one way or another a wire has been swapped, probably at the board end, i.e. it would remain connected to either live or neutral even when it’s allocated disjoncteur is off.
OK, thanks. I can do this quite easily and report back next week.
Digital.
As it happens, I have a couple of 16As spare. It would not be a problem to change them.
More importantly though is the 32mA tripper! May I assume that if this device trips on pressing the test button, it is A1OK and will do its job if called upon??
