If an RCD fails to operate once, should it be considered faulty and replaced?

[flex_m]

I was doing some temp work as a mate, assisting a fully qualified sparks with testing, and an RCD failed to operate. He flipped it off and on, repeated the RCD test and it operated properly, then assured me it didn't need replacing. The fact it failed to operate under fault conditions once makes me think it should have been replaced. Is there a specific regulation that has been ignored here or is it just bad practice to leave an installation that you are aware has such potential faults? Is this serious enough that I should notify the company I was working for (the sparks in question was temp too)?
Cheers

 

[trev]

First question is where was he conducting the test? Out on the circuit or at the load side terminals with the circuit isolated?

 

[Engineer54]

Gummed up mechanical levers by the sound of it. IMHO if it has surcummed to this type of failure, it will in time do so again, so personally i'd change it out!!

 

[flex_m]

Gummed up mechanical levers by the sound of it. IMHO if it has surcummed to this type of failure, it will in time do so again, so personally i'd change it out!!

That was my thinking, do you think it's worth notifying the company I was working for at the time?

 

[NickD]

I was doing some temp work as a mate, assisting a fully qualified sparks with testing, and an RCD failed to operate. He flipped it off and on, repeated the RCD test and it operated properly, then assured me it didn't need replacing. The fact it failed to operate under fault conditions once makes me think it should have been replaced. Is there a specific regulation that has been ignored here or is it just bad practice to leave an installation that you are aware has such potential faults? Is this serious enough that I should notify the company I was working for (the sparks in question was temp too)?
Cheers

The preferred order of test for an RCD is to do the with-the-meter tests, and then only after that poke the test button on the RCD unit. The reason being that poking the RCD unit first can dislodge a stuck lever, that will then go on to pass meter tests which by rights it should have failed. The clear logic there IMHO is that an RCD which without being freed up fails the meter tests, has failed.

In any case common sense says if it can gum up in the period between its last use and your test, it can gum up again in the period between your test and someone's life relying on it working.

 

[telectrix]

whgich is why there'sa label attached saying test quarterly. how many customers are too lazy or too stupid to comply?

 

[NickD]

Though we don't help with CU units often being up there on sky hooks. Wall-mounted test button outside the CU, anyone?

 

[Silly Sausage]

Though we don't help with CU units often being up there on sky hooks. Wall-mounted test button outside the CU, anyone?

Pointless, you've still got to go into the CU to reset the thing!

 

[NickD]

Pointless, you've still got to go into the CU to reset the thing!

OK, so it needs work

 

[trev]

Maybe if this remote switch were connected to a mechanism so that when it was re-energised it could operate a system of levers to re-engage the switch on the RCD.
Anyone want to stump up with a research grant?
Nick, this time next year mate.......

 

[wozz]

replacing it without educating (assuming that like 99.9% no quarterly test has been carried out) is pointless. it may well have failed as it hasnt operated in 10 years, replacing it and hoping the next time its used in 10 years is so far from what it was designed for. the best thing to do is educate the user of the installation replace if you wish although there may be nothing wrong with it if used correctly. no guarantees the new one wont behave the same way if the same happened to it.

 

[NickD]

Maybe if this remote switch were connected to a mechanism so that when it was re-energised it could operate a system of levers to re-engage the switch on the RCD.
Anyone want to stump up with a research grant?
Nick, this time next year mate.......

Right then...two pullcords coming out of the bottom of the CU per RCD, one to test the RCD, one to reset it

 

[trev]

Too simple mate, the people on Dragon's Den will never stump up £quarter of a million for that

 

[Geordie Spark]

whgich is why there'sa label attached saying test quarterly. how many customers are too lazy or too stupid to comply?

:hump:

 

[Marvo]

replacing it without educating (assuming that like 99.9% no quarterly test has been carried out) is pointless. it may well have failed as it hasnt operated in 10 years, replacing it and hoping the next time its used in 10 years is so far from what it was designed for. the best thing to do is educate the user of the installation replace if you wish although there may be nothing wrong with it if used correctly. no guarantees the new one wont behave the same way if the same happened to it.

Agreed, if you replace it without educating then you're addressing the symptoms and not the cause so effectively in a few months time the installation won't be any safer than it is now.

Similarly if the RCD passes after the test button has been operated then surely just education on monthly testing is going to leave the installation equally as safe as replacing the RCD.