RCD Test

[colin8016]

I’ve been asked in install a new outdoor socket for a customer that has a holiday static caravan but I’m confused about the testing side after. Usually I’d complete an RCD tripling time test however the caravan has an RCD on theor own board as well as an RCD on the meter. How can I ensure it’s only the local RCD on the board I test not the one on the external metering

 

[Pete999]

I’ve been asked in install a new outdoor socket for a customer that has a holiday static caravan but I’m confused about the testing side after. Usually I’d complete an RCD tripling time test however the caravan has an RCD on theor own board as well as an RCD on the meter. How can I ensure it’s only the local RCD on the board I test not the one on the external metering

Don't plug the Caravan in prior to testing the socket outlet, and it's not advisable to have two or more RCDs in line. Afterall you are only testing and certifying the alteration to house circuit

 

[colin8016]

Don't plug the Caravan in prior to testing the socket outlet, and it's not advisable to have two or more RCDs in line. Afterall you are only testing and certifying the alteration to house circuit

All static caravans seem to set up in the same way with an RCD in the meter box and then an RCD on the board.

If I unplug the caravan from the meter, removing that RCD, then the entire caravan would be dead. RCD testing is a live test isn’t it?

 

[westward10]

If both rcds have the same rating you cannot guarantee which will trip under test. The only way to test the caravan rcd would be to take the other one out of the equation but you would need to ensure that by doing this you are not removing a level of safety which could lead to a dangerous situation, even if it temporary.

 

[Pete999]

All static caravans seem to set up in the same way with an RCD in the meter box and then an RCD on the board.

If I unplug the caravan from the meter, removing that RCD, then the entire caravan would be dead. RCD testing is a live test isn’t it?

Yes it is, does the socket you have been asked to install have RCD protection at the CU in the house? if so test and certify that job done. The caravan will be subject to ISITEE. See CoP ISITEE. RCDs in series best way to describe it will cause problems.

 

[westward10]

Yes it is, does the socket you have been asked to install have RCD protection at the CU in the house? if so test and certify that job done. The caravan will be subject to ISITEE. See CoP ISITEE. RCDs in series best way to describe it will cause problems.

The outdoor socket is on the caravan, this has nothing to do with ISITEE at all.

 

[Pete999]

The outdoor socket is on the caravan, this has nothing to do with ISITEE at all.

I know it isn't I said the caravan is, and test the New socket his job is done, he is confusing the new socket and the RCD in the caravan supply point, I sure you understand, but will continue to argue the point.

 

[davesparks]

The only way to test the caravan rcd would be to take the other one out of the equation

That's not the only way, connecting the earth lead of the tester to the incoming N of the second RCD will allow testing of the second RCD without tripping the first RCD.
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I’ve been asked in install a new outdoor socket for a customer that has a holiday static caravan but I’m confused about the testing side after. Usually I’d complete an RCD tripling time test however the caravan has an RCD on theor own board as well as an RCD on the meter. How can I ensure it’s only the local RCD on the board I test not the one on the external metering

Which board are you testing, where is it electrically in relation to the other RCDs?

If testing a downstream RCD you can connect the earth lead of the tester to the incoming neutral of the RCD under test, the test current will appear balanced to the upsteam RCD and not trip it.

 

[westward10]

I know it isn't I said the caravan is, and test the New socket his job is done, he is confusing the new socket and the RCD in the caravan supply point, I sure you understand, but will continue to argue the point.

The OP isn't confused at all his post makes perfect sense.

 

[chrisdungan]

I’ve been asked in install a new outdoor socket for a customer that has a holiday static caravan but I’m confused about the testing side after. Usually I’d complete an RCD tripling time test however the caravan has an RCD on theor own board as well as an RCD on the meter. How can I ensure it’s only the local RCD on the board I test not the one on the external metering

Kiwi inspector here. When I test a caravan RCD where the supply socket also has an RCD I use a modified double wound isolating transformer with the output neutral and earth connected together so that the van RCD is isolated from the house RCD ( so that doesn't trip)and so that the caravan has a N/E reference. That way I'm testing just the caravan RCD without involving the supply side.

 

[EricMark]

Never needed to do it, but I think I would use my jump start pack, however not sure what wave form it produces, also use it to test testers work. Need adaptor 13A to 16A but that is easy enough.

 

[Lucien Nunes]

As Davesparks describes, there is no problem testing RCDs in series at the RCD itself, as the tester can be connected to dump the test current back into the neutral so that there is no imbalance at the RCD upstream. Testing the upstream RCD doesn't affect the downstream one. I don't know why RCDs in series are thought to be a big deal. Sure, it's good design to ensure that only one device trips under any one particular fault, but an outdoor shoreline is a good example of where the double RCD is inevitable and it works just fine.

I think I would use my jump start pack

Inverter? I would be cautious. The calibration of the tester is likely to be completely off with the kind of output many inverters produce. The so-called 'pseudo-sine' isn't a sine wave, it's a kind of square wave with gaps to give it the correct ratio of peak / RMS values, but obviously lots of harmonics. Even a true sine output may be very noisy.