Ketech 65 trips RCD when Zs testing at Light switch

[KingKenny]

Hi everyone - First post on here from a newcomer to the trade, so please bear this in mind when replying. ------- I was carrying out an Inspection and Test on an install today and wanted to get a ZS reading at a light switch. I couldn't get a good enough connection with the crocodile clips, so had to use probes. ----------------------------------------------- My testing kit is a Kewtech KT65 which requires three leads to take ZS readings (as far as I can tell...). BUT ... when I apply the probes (Brown on SW L (L1), Blue and Green at the Earth Terminal, it immediately trips the RCD before a reading can be taken. ------------------------------- Taking a ZS reading at a socket outlet is no problem as the kit has a bespoke lead with a three pin plug for this purpose. Is there anything I can do to get around this? --------- Thanks KK

 

[KingKenny]

I forgot to add - I have a Ze reading at the board and a good R1 + R2 reading at the last lighting point, so in this sense, I'm happy - BUT ... I wanted to take a Zs at the lighting point to sense check all is as it should be. ---- Thanks again, etc..!

 

[Harryb]

Blue probe to earth?

 

[pistolpete]

Blue on neutral hence 3 probe test???

 

[jamesBoater]

As above, you need live neutral and earth to do the test , although some mft,s can do 2 lead no trip , ie megger 1730.

 

[KingKenny]

Thanks to everyone who has replied so far....... Well there is no 'neutral' as such, is there? You have COM and L1 (switched Live) and Earth. The Kewtech manual has the blue and green crocodile clips attached to the earth terminal in the switch backbox and the brown probe to SWL. Must be a special Kewtech backbox with loads of generous space to attach two croc clips then coz it's impossible with the ones I have....

 

[Octopus]

Thanks to everyone who has replied so far....... Well there is no 'neutral' as such, is there? You have COM and L1 (switched Live) and Earth. The Kewtech manual has the blue and green crocodile clips attached to the earth terminal in the switch backbox and the brown probe to SWL. Must be a special Kewtech backbox with loads of generous space to attach two croc clips then coz it's impossible with the ones I have....

So is the Kewtech picture correct????????

 

[jamesBoater]

ok in that case are you sure you have the tester set to the correct setting, silly question i know but the meggar i use can be set to 3 diff settings for loop testing

 

[KingKenny]

... at the switch that is. I didn't attempt to take Zs at the rose where there IS a neutral ..... Hmmmmm....... Thanks guys.

 

[stuartcourt]

I expect in the kewtech picture he or she was doing a PSC test or the like

 

[KingKenny]

Could be stuart - The manual was pretty poor to be honest.

 

[Badged01]

With the Kewtch KT65 you need to seperately connect to the L, N, E to get a reading.

At your switch you dont have a N so you cant do the test!

 

[pistolpete]

With My Megger 1730 you can no longer do 2 lead test on lo for rcds as its not accurate enough. 3 lead on Zs tests with any rcd :-(

 

[telectrix]

With the Kewtch KT65 you need to seperately connect to the L, N, E to get a reading.

At your switch you dont have a N so you cant do the test!

nail on head there. 3 lead test needs L,N and E connected to tester for it to work, same with the megger 1552/3.

 

[Geoffsd]

You can do it with a Fluke - N & E leads to Earth.

Is it just the Kewtech for some reason?

 

[Deleted member 72666]

Am I missing something here, Zs readings should be taken at the furthest point which would usually be at the light fitting in this case?

 

[KingKenny]

Am I missing something here, Zs readings should be taken at the furthest point which would usually be at the light fitting in this case?

No, mate - You're not missing anything - it was the end of a long day for me, I was getting familiar with the almost brand new KT65, let alone my first full end-to-end test of an installation I'd done. The manual indicated I could take the reading at the switch and I missed the obvious. My fault. -------------- I'm not due back on site till next week, so I'll take the reading then. I SHOULD have copped it when I successfully took RCD trip readings at the same light switch about 20 minutes afterwards on L, N and E, but like I say - I had a brain trip!!! --------------------------------------------------------------------
genuine Thank You to everyone who responded. -------------- KK

 

[virge]

You can do it with a Fluke - N & E leads to Earth.

Is it just the Kewtech for some reason?

I have a fluke 1653 ,am i understanding right then that you can test for zs at ceiling rose with N & E leads conected to Earth in the ceiling rose and L conected
to L or SW Live

 

[Geoffsd]

I am not saying you should, because there is a neutral at the rose

but at the switch it will work and confirm the earth is good.

 

[virge]

Hmm think i will give that a go ,any more handy tips Geoffsd ,can you tell me the difference between a short and a short circuit sounds dim i no but just need to understand the meaning (still at college) thanks