chris French wrote:
In message , "Dave Plowman (News)"
writes

But a heavy current draw like this should be easily found with a simple
DVM - after disconnecting the ring from the CU of course.

OK, how would I go about it? I've got cheapy multimeter.

Personally I would prefer to start by using a clamp meter on the running
circuit - clamp round the live(s) at the exit from the MCB and take a
direct reading of the current. This will verify what the real load is.

One test with a DVM would be to disconnect the circuit (live and
neutral) at the CU and then measure the resistance between live and
neutral.

If the circuit was drawing 40A at 240V, then you may see a resistance as
low as 6 ohms. However this does assume that the load you are seeing
will be visible at the low voltage of the DVM, and also that it is
purely resistive[1].

If you can see the load with the DVM like this, then it ought to be a
case of just breaking the circuit at various places until you isolate
where it is. So if it is a ring for example, splitting in the middle and
seeing which leg of it at the CU shows the low impedance load would
immediately eliminate half the circuit.

[1] A large reactive load would be an interesting possibility in that it
would not need to be accompanied by a large power dissipation. However
your electricity meter ought not record this as power consumption.


--
Cheers,

John.

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