Well, I suppose if we are arguing about semantics, if an RCD is duff out of the box is it not an RCD
Its still a RCD, but it is faulty.
Yesterday a farmer had 17 sheep. During the night, all but 9 die. How many sheep does the farmer have now?
Replacing a rusty old garage CU
- Thread starter Googleberry
- Start date
Its still a RCD, but it is faulty.
Yesterday a farmer had 17 sheep. During the night, all but 9 die. How many sheep does the farmer have now?
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When RF Electronics tells me which of the many RCD failures mode is 'duff' then I'll respond, as long as he does it politely It's not a very technical description, forgive me for not taking it seriously, which is why I put a smiley at the end of my answer. He can answer for himself, I am sure.
It's not a very technical description, forgive me for not taking it seriously, which is why I put a smiley at the end of my answer. He can answer for himself, I am sure.
Duff means broken.
Not functioning properly, or at all.
Not functioning properly, or at all.
it is worth noting that the 'test' button on RCD's / RCBO's is only there to test that the mechanism is not seized. When a 30mA RCd / RCBO is installed it is tested 6 times with a meter that records it's disconnection speed in miliseconds. Almost every RCD will have a different reading. some ones won't disconnect in time, some wont disconnect atall, even if the 'test' button switches it off.
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I am forced to assume that:
Duff not functioning properly = out of spec.
Duff not functioning at all = open circuit or push button test does not disconnect.
If Duff not functioning at all then replace with another RCD. Repeat test for Duffness.
If Duff not functioning properly then it will be safer than not having an RCD at all.
What utter twoddle. Duff means its broken and you need a new one. Full stop.
Interesting comments 1john.
FYI, and just out of interest, I connected an 8k resistor from live to earth via a fast reed relay, and connected a dual-channel oscilloscope across the resistor. The second oscilloscope channel was connected directly across the mains. (Yes, it's got a 500V RMS input!) With the scope nicely synced to the mains, I was able to trigger the reed relay at any point in the mains cycle. Regardless of when, the RCD tripped within two mains cycles every time, which means that it operates within 40 milliseconds, which is good. However, I must point out to you that even if I hadn't tested it, the probability is that it would have worked and therefore improved safety.
Even if an RCD takes longer than it should, it would still likely provide worthwhile protection. To illustrate this: if you were required to use power tools outdoors at a house with an old fuse box on a damp day, and you found an RCD plug lying around, you would use it for your extension lead even though you had nothing more than the built-in test button to reassure yourself with, because the probability is that it would benefit you, and certainly not disadvantage you at all, so I think your criticism about not testing is somewhat OTT!
You are Nitros and I claim my £5.
It's in the post.
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