Anybody notice the changes to 643.7.1 and 643.8 when it comes to RCD testing. In the note it says that "Regardless of the RCD type, effectiveness is deemed to have been verified where an RCD disconnects with in the time stated below with an alternating current test rated at residual operating current I△n"
So the minimum requirement is to set your instrument to RCD type AC and carry out the test even if you have a Type A or Type B RCD.
In the 8th Ed of GN3 (2018), there was no indication of whether the test button should be pressed before the tripping time test.
The 9th Ed of GN3 (2020), Section 2.6.18, says:
Before using a test instrument, the RCD test button should be pressed. This provides basic information that the RCD is functioning, and will help avoid danger that may occur during test if the RCD did not respond.
Test button last in case the RCD or RCBO explodes on the initial test.
Been there done that.
Something long and pointed is handy for pressing the test button rather than a finger.
This is one of those cases where there's no right answer ... for example:
Yep, test with instrument before using test button.
So, use an instrument with a test method that returns a fault down a protective conductor ... without checking the protective device is working?
Some devices with RCDs say "Test before use": https://www.screwfix.com/p/british-general-900-series-13a-2-gang-sp-switched-passive-rcd-socket-white/3133j
Safer not to follow manufacturer's instructions?
This simulates a real "natural" fault situation.
Far from it. And the 1x test does little more than "push the button" (the test button for a 30 mA RCD can't generate more than 1.66 times the ampere-turns produced than that generated by the residual current tests - for other values it's 2.5 times).
Nothing has actually changed has it, there is just some clarification?
We still do times five or 250 mA when we need to.
The 9th Ed of GN3 (2020), Section 2.6.18, says:
Before using a test instrument, the RCD test button should be pressed. This provides basic information that the RCD is functioning, and will help avoid danger that may occur during test if the RCD did not respond.
That is a shame. Most meters handle a non-tripping RCD quite gracefully and just time out after a second or so and issue a warning. The internal test resistors inside the RCD do not generally have any protection however, preferring if the contacts are stuck to burn out violently and startle the button pressor with a crack like a small banger of the kind kids used to bring back on the ferry from day trips to France..
I presume the authors of the GN have not actually done enough testing to encounter that failure mode.. It can be quite unnerving. I'd strongly recommend reversing that in the next edition, and saying why.
Mike.
My apologies for being unclear - I was referring to the generic schedule of test results. IMHO, testing is of limited value if the result is not recorded, but there is room in the "remarks" column. I might add that on the whole I am please that the generic schedule has been split in two - the columns were getting a bit crowded.
Agree Mike, can't see a real world problem here, only lots of theoreticals, a bit like my useless Consultant.
So, does dropping the previous multitest requirement mean that we should see much cheaper testers enter the market? Every cloud and all that jazz.
"So, use an instrument with a test method that returns a fault down a protective conductor ... without checking the protective device is working?"
The current is only allowed to exist for a very short period of time, as designed into the meter operation. That is a safety feature. Obviously we would take safety into account before carrying out any tests, e.g. warn householders etc.
Z.
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