On 2018-01-05 15:43, newshound wrote:
On 05/01/2018 08:52, Roger Hayter wrote:
newshound wrote:

Got a heating element in a wallpaper stripper which is blowing 30mA RCD.

Testing live to earth on an old (but "electronic" rather than wind-up)
Megger (which seems to provide 320 volts DC) gives ~ 5 MegOhm.

Testing on a DVM gives ~ 200 kOhm, corresponding to a little over 1 mA
leakage current on mains.

Can you test both instruments on a one megohm high voltage resistor?

That test was with the element removed. I agree that 5 meg is defective,
but wouldn't necessarily trip an RCD. Didn't have any suitable resistors
to hand when checking...

You've already told us you've got one. Your DVM should have a constant
input resistance (usually 10 MOhms, but check the manual). So, while
you're reading the 320 V output of the Megger on your DVM also check the
Megger to see what resistance it sees looking in to the DVM.


--
Graham Nye
news(a)thenyes.org.uk