Professional install flagged by electrical inspection

[ericmark]

Seems odd they'd be configured that way

Would have thought keep current on the live conductors

If test current is to earth, it actually proves there is an earth to start with.

In the consumer unit we can near enough guarantee there is an earth, and the volt drop is low enough for the device to work.

But at the socket, we want to be sure enough power to work the device, and that the earth is there.

Often we rely on a socket RCD, as there is no overload which would work within the required time, this is the case with my RCD sockets, the 5 kW inverter feeding the sockets could never supply even enough power to trip a 10 amp MCB on the magnetic part of the trip, 5 kW at 230 volts = 21.8 amps, and a type B10 MCB needs 50 amps to trip the magnetic part of the trip, and the thermal part is too slow.

And if we have a load of 52 amps (13 amps x 4 outlets) the inverter will likely lock out, but as to how it would react between 21.8 and 52 amps, I simply don't know, I have had generators which with a rapid load applied have dropped voltage, so the overload has failed to open, and that is why we fit active RCDs so if the voltage drops they fail-safe.

These scenarios do not really apply here, but it does explain why the test is to earth.

So no more than 50 volts AC to earth, so at 30 mA at 50 volts it must trip, 50/0.03 = 1667Ω and 254/1667Ω = 152 mA so to ensure even at 50 volts it will trip it means it will also trip the device even if it needs 152 mA to trip it, so it is unlikely to detect when DC is causing the device to need more current to trip.

It is possible it only allows for a volt drop to 200 volts, so looking at 40 mA, but it is unlikely the test button only allows 30 mA to flow, so it is only to check the mechanism has not stuck.

It also seems that reverse current flow, will cause damage to a mono-directional RCD when the test button is pressed, I don't have money to throw away testing if they burn out if a RCD tester is used.

charity building

So we are looking at someone else's money, it is all well and good, as I have done, making a risk assessment with ones own home, to decide if the type AC RCD should be replaced with a type A, and I have only fitted type A where a socket on that circuit may be used to charge my son's EV. I have assessed the risk, and I feel the chance of a fault to earth accruing at the same time as some appliance has also allowed DC to flow, with 14 RCBOs in the board is very low, so I still have 12 type AC RCBOs in the board.

I would think not domestic, so in real terms only someone who is trained should touch the electrics, I know with the heritage railway I work on, my qualifications had to be viewed and photo of them kept on record, most volunteers are not allowed to touch electrics.
There is a register kept as to skills, be it using a grinder or a cash till, records have to be kept, including any tool box talks attended, not to do this is like a red flag to a train, everything stops.

So if an electrician says xyz is not safe, and we all think it is safe, then the electrician who counters the order, would need to be trained to a higher level.

So in this case, the installers would need to return and fix it. Or someone else would need to fix it. Not looking at if dangerous or not, I am looking at who could countermand the decision of the EICR inspector.

If there is a clear fault, then fixing it is the way forward, it only requires a minor works certificate raising to show work has been done.

Where the problem lies is where there is no real fault, can't fix something which does not need fixing, and also if no real fault found, how does the second guy know it is not something he has missed?

 

[SimonH2]

I used the test button on an MK 10 mA metalclad RCD socket, and it also tripped the 30 mA and 100 mA feeding it, so the test button only tests it will mechanically trip, it does not check if within spec.

Actually, it's checked that it will detect the current imbalance through the detector and trip.

We've had discussions before here about series RCDs - typically it's a crapshoot as to which will trip. Unless one is a time delay (for selectivity), then anything between one and all of them is possible. Assuming the imbalance is enough to trigger the 100mA one, then all will detect the fault, it's a matter of device characteristics as to whether any of them have NOT already triggered the mechanism to open the circuit by the time any of them actually does open the circuit. I.e., there's a time lag while the mechanism physically operates after being triggered - and during this time, the fault current still flows triggering other RCDs in the circuit.
Let's just pick some numbers to make things easy. Let's say the electronics requires a fault for 10ms to trigger, and the mechanism takes 10ms from trigger to opening the contacts. You press the test button, after 10ms one or all will have detected the fault and triggered the mechanism. The fault still flows for a further 10ms, so by the time the circuit opens at 20ms, all the RCDs are guaranteed to have tripped even if their mechanisms haven't yet opened the contacts.
That's still the case if one of them takes 15ms to detect a fault - 15ms is still within the 10-20ms window where one or more other devices are operating their mechanism(s). Even though the fault may have been removed before it's contacts open, the mechanical movement to do so has already started.

As we know, that's why we have 100ms delayed RCDs - to give other (downstream) devices time to trigger AND open their contacts (thus removing the fault) long before the upstream device triggers.

As to why the test went line to earth rather than bypassing the coil, I don't know, but clearly some do.

Others have given an opinion on that. Seems reasonable to me.

 

[morqthana]

What is there to lobby for?

Test equipment manufacturers are on the ball and are kept abreast of all the changes so they can bring up to date equipment to the market in good time.

But there are no changes test-wise regarding RCD types, so existing test equipment is still valid for the job.

I find it both shocking and depressing that I have to spell this out in such simple terms.

1. Different RCD types are designed to detect different types of faults, or faults on circuits carrying more than just simple AC.
2. It is considered that these different capabilities are required for safety reasons, for example to avoid the problem that a type AC RCD can be prevented from working by a DC component, a feature exploited by no-trip loop impedance testers.
3. Since RCDs are supposed to work, and they are required to be tested to show that they work, it would seem a no-brainer that they should be tested using simulated faults which reflect the real faults they are supposed to detect.
4. Since some test equipment manufacturers make testers which do perform tests tailored for different types of RCD, I would be surprised if they were not lobbying "the authorities" to update their regulations to mandate such testing.

Do people get it now?

 

[pete01]

I find it both shocking and depressing that I have to spell this out in such simple terms.

1. Different RCD types are designed to detect different types of faults, or faults on circuits carrying more than just simple AC.
2. It is considered that these different capabilities are required for safety reasons, for example to avoid the problem that a type AC RCD can be prevented from working by a DC component, a feature exploited by no-trip loop impedance testers.
3. Since RCDs are supposed to work, and they are required to be tested to show that they work, it would seem a no-brainer that they should be tested using simulated faults which reflect the real faults they are supposed to detect.
4. Since some test equipment manufacturers make testers which do perform tests tailored for different types of RCD, I would be surprised if they were not lobbying "the authorities" to update their regulations to mandate such testing.

Do people get it now?

We get it but its not whats required, someone much cleverer than me and you has worked out that the AC setting is adequate for the test.

Do you get it now?

 

[morqthana]

We get it but its not whats required, someone much cleverer than me and you

Please do not assume that everybody is like you.

has worked out that the AC setting is adequate for the test.

Have they indeed.

IEC 61557-6:2019

webstore.iec.ch

 

[mikehammer69]

I find it both shocking and depressing that I have to spell this out in such simple terms.

1. Different RCD types are designed to detect different types of faults, or faults on circuits carrying more than just simple AC.
2. It is considered that these different capabilities are required for safety reasons, for example to avoid the problem that a type AC RCD can be prevented from working by a DC component, a feature exploited by no-trip loop impedance testers.
3. Since RCDs are supposed to work, and they are required to be tested to show that they work, it would seem a no-brainer that they should be tested using simulated faults which reflect the real faults they are supposed to detect.
4. Since some test equipment manufacturers make testers which do perform tests tailored for different types of RCD, I would be surprised if they were not lobbying "the authorities" to update their regulations to mandate such testing.

Do people get it now?

Morqthana , you're an excellent poster

Maybe let's all back off on the arguments .Christmas is on the way

 

[pete01]

Please do not assume that everybody is like you.

Unfortunately

 

[SUNRAY]

Unfortunately

 

[morqthana]

Maybe let's all back off on the arguments

Can you credibly show that me saying "can't believe that the companies who make such testers aren't lobbying for it" when I learned that RCD testers don't have to test different types was starting an argument?