Metrel MI3000 Zs(rcd) tripping

gazdkw82 · Dec 17, 2018

Anyone had any experience of metrel testers tripping an RCD when doing a Zs when you have the rcd no trip function on?

It happened the other day on my 2391 assessment but the college tester did the same so I assumed it was the college rig.

Just wired up a cooker for my niece, can't do a Zs. Tested the rcd and that's fine.

Pain in the rear.

Strima · Dec 17, 2018

We have five of them and have never had an issue trying to do no trip Zs.

gazdkw82 · Dec 17, 2018

Uumm. I'll another look tomorrow.

SparkieMarky · Dec 17, 2018

Is the RCD part of a split load arrangement? It sometimes happens that existing and test earth currents add together to trip the RCD or RCBO, especially if the RCD is on the sensitive side. Have you ramp tested the RCD to see if it is on the sensitive side?

gazdkw82 · Dec 17, 2018

It's an RCBO. No load on the circuit

SparkieMarky · Dec 17, 2018

The RCBO might be on the sensitive side so worth ramp testing it to confirm that isn't a factor. It's also worth checking the tester on other circuits to see if it causes the issue with any RCD/RCBO as there is always the possiblity that it could be the problem or at least twards the extreme end of spec so will cause a trip most of the time.

You could always by pass the RCBO for the test by temporarly swapping it out for and MCB.

gazdkw82 · Dec 17, 2018

I ramp tested it. 22ms.

SparkieMarky · Dec 17, 2018

You need to change the meter settings so that it gives you the tripping current in mA as opposed to time (my old Metrel Eurotest XE has a ramp test option that allows for this). Most no testers no trip loop test will use a current of around 15mA so if the RCD is sensitive or your tester is for some reason pushing a current higher than 15mA then you are likely to end up with a trip.

gazdkw82 · Dec 18, 2018

Sorry sparkiemarky, it was meant to be 25ma not Ms.

timbobelfast · Dec 18, 2018

gazdkw82 said:
Anyone had any experience of metrel testers tripping an RCD when doing a Zs when you have the rcd no trip function on?

It happened the other day on my 2391 assessment but the college tester did the same so I assumed it was the college rig.

Just wired up a cooker for my niece, can't do a Zs. Tested the rcd and that's fine.

Pain in the rear.

Are you using the three leads when taking the Zs?