- Reaction score
- 2,089
The ramp test probably tests between N and Cpc ?
Did you try using the mft to leak up to the tripping point of the rcd ? And if so was the tripping point of the rcd the same as the ramp test ?I know this is a tangent and a rabbit hole, but you know me - I had to explore this idea further....!
A non-rcd protected socket, two different MFTs, a calibrated multimeter in series with CPC (set to Max), and a clamp meter (set to Max):
View attachment 111884View attachment 111886View attachment 111885View attachment 111887
Conclusion: in this environment the the clamp meter is pretty close to the multimeter. The cause of the effect we both saw is likely not due to the clamp meters accuracy.
I set the clamp meter aside, and introduced an RCD that ramp tests at 25ma, then used one MFT in calibration mode to perpetually leak 15ma to earth, then the other MFT in ramp test mode. Interestingly the latter still ramp tests at 25ma even though it's counterpart is leaking 15ma. So I can reproduce the issue at home very easily.
I'm wondering if there is some sort of phase offset shift inside the MFT when ramp testing as what seemed like a perfectly logical idea simply doesn't work! So it seems we use one or the other but don't try and be clever with both, for reasons as of yet unknown.