zs test keeps tripping rcd

[crow11]

fitted a new c/u and put a new ring main in kitchen last week ready for my assessment in the morning, everything tested ok and zs tested ok then, sent meter in for calibration check last thursday and picked it up today (megger 1552) certificate says everything passed no adjustment needed, so i thought i would go back to the job and just redo some basic testing and now for some reason it won't let me do a zs test just keeps tripping the 63A rcd, r1 + r2 + rn and R1+R2 are all the same as when i tested last week as is ir and continuity, nothing as changed at the job at all, iv'e switched every other circuit of and unplugged everything and just left the new ring main switched on with everything unplugged and still trips the rcd, tried it on the other side and it trips that rcd as well, it will let me do a no trip 3 lead zs but just totally baffled as to why it now trips it out on the normal zs test

 

[plugsandsparks]

Sounds like its working fine, my tester always trips RCDs unless I use the no trip function.

 

[HappyHippyDad]

fitted a new c/u and put a new ring main in kitchen last week ready for my assessment in the morning, everything tested ok and zs tested ok then, sent meter in for calibration check last thursday and picked it up today (megger 1552) certificate says everything passed no adjustment needed, so i thought i would go back to the job and just redo some basic testing and now for some reason it won't let me do a zs test just keeps tripping the 63A rcd, r1 + r2 + rn and R1+R2 are all the same as when i tested last week as is ir and continuity, nothing as changed at the job at all, iv'e switched every other circuit of and unplugged everything and just left the new ring main switched on with everything unplugged and still trips the rcd, tried it on the other side and it trips that rcd as well, it will let me do a no trip 3 lead zs but just totally baffled as to why it now trips it out on the normal zs test

Hi Crow..

Think I must be getting this a bit wrong as a bit confused! Are you saying that you get a Zs reading when you test on the 'No trip' function? If you are then just use that result. Its always going to trip the RCD if you dont use the 'no trip' function. The 'normal' Zs function on the MFT is for circuits that are not on an RCD.

 

[telectrix]

on RCD circuits you must use 3 lead no trip setting with a 1552. or the RCD will trip

 

[i=p/u]

you have to use no trip when rcd involved

 

[HappyHippyDad]

on RCD circuits you must use 3 lead no trip setting with a 1552. or the RCD will trip

I have NEVER managed to reply to a thread before you Tel. I am in shock! :dizzy2:

 

[HappyHippyDad]

you have to use no trip when rcd involved

Especially on a TT :wink_smile:

 

[i=p/u]

It's sad star if affairs when you can't grasp it, just push the button write then number down doesn't work for me nursey))

 

[Silly Sausage]

Sounds like his MFT was possibly faulty pre-cal and they've tweaked it without telling him.

 

[telectrix]

I have NEVER managed to reply to a thread before you Tel. I am in shock! :dizzy2:

first for everything, mate. and if you are in shock, you've fitted the RCD the wrong way round. :lipsrsealed2:

 

[i=p/u]

Do you get what I'm saying vw camper man

 

[HappyHippyDad]

Do you get what I'm saying vw camper man

Didn't have a clue! But it sounded friendly so you got a like..

 

[Lucien Nunes]

P=IU, I think he's looking a bit more deeply, i.e. why has it changed, if it's OK now then perhaps it was giving wrong results before.

So I think the specific question would be 'Why did my MFT not trip the RCD when I was doing high current Zs tests, until its recent calibration, despite the fact they claim not to have done anything to it.' That is a good question but you don't know for certain whether the MFT or the RCD behaviour is changed. You might be onto a loser trying to explain it, although if it were me I'd try to get access to another RCD that I had done a test on in the recent past, and verify the accuracy of the results with the tester as it is now. Just in case it was not operating correctly. Did any of the results look odd, before the calibration?

 

[telectrix]

it's quite possible that the OP has slipped up. may have been doing readings using the plug in lead, not realising that it was a 3 lead test and now , post calibration has been using the probes. does that make sense?

 

[crow11]

think archy might be right in his theory, before calibration test it would do a zs test on a rcd circuit, so can only think something as been adjusted on calibration test, cause since i got it back it won't, i had a calibration check at the same place last year and it still did zs ok then on rcd circuits, i must of had a special megger lol cause the reading for the zs where what you would expect them to be so it wasn't like it was giving me false readings