RCD Testing

[owendrees]

Just completed a board change on TT system. All the results ok until I tried a 5x test then my tester gave me a reading saying ERR4 Uo>50Vac and RCD would not trip. I have a FLUKE tester and wonder if anyone else has had a similar experience. would appreciate some views and advice.

 

[slocm3105]

Voltage is exceeding the touch voltage of 50V and not tripping. I've had this a couple of times and changing the rcd gerally does the trick. However, try turning off all loads and testing at the terminals on the rcd. Sometimes a faulty load can cause it not to trip.

 

[owendrees]

Nice one. Will try testing at rcd. If problem continues then I will try changing RCD.

 

[xraytek]

Before changing the RCD you might also want to take a loop impedance measurement.
Maybe Zs is >330 Ohms which is why the voltage goes above 50 when tested at 150mA.