Andrew Gabriel wrote:
In article .com,
writes:

Testing an RCD (part of a split-load CU) I found that at the rated
current (30mA) it would trip anywhere between 16-17ms to not at all
(even with the meter set to the 2s range). Suspecting the RCD I
swapped
in another from a spare box (same make - Clipsal - but almost
certainly
different batch as I bought them at different times from different
suppliers). However the other RCD showed much the same behaviour.
Both
tripped reliably at 50mA.
Is this typical, or are both faulty? (Is Clipsal crap? :-)


It's not typical -- I normally find they trip within
20ms at the rated trip current (not used Clipsal though).

Each & every time? It tripped within 16 or 17ms first couple of times,
but trying repeatedly I got non-operations. Maybe the RCD was getting
tired? ;-)
As I say though, I did test on different samples.

Whitfield says "100% of rated ... must ... trip within 200ms" and
"150mA ... 40ms" which suggested to me that a (say) 30mA 30ms RCD
should trip at 30mA, but doesn't have to do so within 30ms, but would
trip within this time at higher currents.

Is your RCD tester calibration out of spec?

Just recently been calibrated so I'd hope it'd be OK. Will try again on
other RCDs (like this house cct, after I've logged off :-)