How to test a 3 phase rcd

mbelec · Oct 4, 2015

Hi I need to test some three phase rcds
my test meter (old megger) has the standard single phase kettle plug on it fine for single phase rcds to test from a socket outlet.
to test a three phase rcd do I need to rig up an industrial plug top and wire to three single phase socket outlets One on each phase, or is there something I can buy specifically for this purpose or can you get probes to test straight onto the rcd terminals, how do you guys do this?
thanks

Paul.M · Oct 4, 2015

The 3ph RCD has the same mechanical RCD parts over all 3 phases to close off all 3 phases at the same time.

You can test any phase and log them on your cert.

markc123 · Oct 4, 2015

What Paul said.

I also suggest you re-visit how to test a single phase RCD. Plugging into a socket isn't best practice.

Mark

davesparks · Oct 4, 2015

Considering that an RCD test should always be carried out at the terminals of the device itself with the outgoing conductors disconnected i'd suggest you need to brush up on your testing methods!

Paul.M · Oct 4, 2015

Plugs? erm..... Lets not forget that you are testing the RCD and not the circuit.

mbelec · Oct 10, 2015

Thanks for replying to my post about testing 3 phase rcds

i got in touch with megger and they suggested I make up a lead for my meter using a kettle lead and an industrial plug top, I presume they agree with you to test any 1 phase. They also sent me their general info about testing 3 phase systems which conflicted and suggested testing each out going phase of an rcd and recording the slowest.

i have also referenced in the Niceic inspection and testing guide book, and they confirm that rcds can be tested from any convenient point in the circuit, not as described above on this forum by disconnecting all outgoing circuits

you guys may be getting confused with advice about disconnecting loads not disconnecting circuits

I think it an important subject to get right

if there are any other forum members with a view on this or if anyone can help point me towards any further reference materials
it would be much appreciated

telectrix · Oct 10, 2015

i always test at a socket with all loads dissed. i challenge anyone to ensure maintaining good contacts using probes for the duration of a RCD auto test while resetting the RCD 4 times.

davesparks · Oct 10, 2015

telectrix said:
i always test at a socket with all loads dissed. i challenge anyone to ensure maintaining good contacts using probes for the duration of a RCD auto test while resetting the RCD 4 times.

It's only one probe to hold on the outgoing terminal, the n and e can be croc clips on the respective bars.
Plus you can remove and replace the probe between each test, the tester will only perform each test once the stable voltage is applied to the probe