RCD tripping.

[Dave Plowman (News)]

Woke up this morning to find the RCD in the split load CU had tripped. Turned out to be something on the 1st floor ring. With that MCB off, no problems. Put it to on, and the RCD tripped again.

Unplugged everything on it. Fine. Slowly re-instate things and haven't found the problem one(s) yet. I suspect it is a current sensing 4 way outlet in the spare room which feeds the AC system there.

It's only when you do this sort of thing you realise just how much stuff you have. ;-)

Wondered if there was some form of 'leakage' tester I could buy or make? To find out the actual fault current in each and every thing which is plugged in to it? And what is acceptable - as I realise some things will have some anyway.

[spuorgelgoog]

Any megger / insulation tester and test between (L+N) and E.

15 mA may trip a 30 mA RCD and that's 16 kOhm at 240 volts.

Permitted leakage for PAT:

Class Type Max Leakage Current

1 IT, Movable, Stationary, & Fixed 3.5mA 1 Heating & Cooking 0.75mA per kW* 2 All Types 0.25mA

• to a maximum of 5mA

Owain

[Dave Plowman (News)]

Thanks Owain. Did just wonder if there was a device you plugged the appliance into which then gave a direct read out of leakage current.

[Brian Gaff (Sofa 2)]

But hang on a moment, many devices have mains filters that as a transient would fail those tests, as they have capacitors in them which have to presumably charge and discharge on each cycle of the mains. Brian

[Roger Hayter]

This is best analysed as an AC current (sic) rather than as transients, and must meet the limits set. Hence filter capacitors to earth have to have a lower value than capacitors across live and neutral, which latter don't contribute to earth leakage.

[Brian Gaff (Sofa 2)]

Hmm, well, that lets the ones I used to build be non starters then. grin. Brian

[John Rumm]

You can get high sensitivity clamp meters that will (with the aid of a short extension lead with the individual insulated wires made accessible) allow direct measurement of leakage if its directly to the circuit earth (obviously it won't see leakage via a parallel path to earth)

[tony sayer]

In article [e-mail]>, Dave Plowman (News) [e-mail]> scribeth thus

Don't overlook that odd Neutral to Earth leakage short which can cause quite some fun and games as the load increases in the system!..

[tabbypurr]

PAT tester or megger. Or you can do it at mains voltage with just a meter & protecting resistor. Or use a microwave turntable motor as a 0-1000v supply.

But a multimeter, they pick up a useful percentage of faults.

NT