Megger 1552 strange readings!!

[badwolf]

Hi Gents, I could do with a bit of advice!

I've recently changed my meter to a megger 1552, and have today, carried out my first pir with it. Dead tests are fine, its when i got to testing the loops and rcds. Using the no trip loop test i get 22.9k ohms doing either a ze/zs, but when using the hi loop function i get .12 ohms ze on a pme. i cant use hi loop function to test the zs on other circuits as they are all on rcd protection, and when using the rcd test, it starts then stops, displaying 55volts?. I've double checked still got the same results, so i drove to my parents home 2 mins up the road and got exactly the same results, so i thought it was the meter, i got home and carried out the same tests in my house 5 miles away and it all works perfectly?? is it the meter, the supply in the village or the tester!

Any ideas would be appreciated!

 

[telectrix]

could be faulty or missing earthing in the village. what readings did you get for Ze.? and did you have the green lead in the correct port on the 1552.?

 

[badwolf]

Thnks for the quick response telectrix!

ze achieved through "hi" loop was 0.12, cant do a hi loop for zs. I used the plug lead to test the zs on the socket outlets and cooker panel using non trip and got silly value, used the seperate leads for lights and got the same value, plug in all the right holes!

 

[sparkinlee]

The 55 volt message on the Megger when testing RCDs means that it's not detecting voltage between L&E and/or L&N. Double check you're connecting the test leads correctly (unless you're using the plug in socket lead!), and measure the voltage present to check they are what you'd expect.

I've also been caught out before thinking the tester was up the spout, when all that had happened was that a lead had pulled out of the tester because I over-stretched!!

 

[badwolf]

hi sparkinlee, i was using the plug lead at the time and when it started playing up i checked the connection and retried and still it would start happily and then give up like it got bored and went to the pub! Dont really know what to do about it!

 

[sparkinlee]

I've got the Megger 1553, which is identical to the 1552 but with the addition of Bluetooth functionality (which I've never used anyway!). Things which have caught me out in the past (most of which turn out to make me look a bit foolish) include
- batteries not having quite enough juice in them
- internal fuse blown
- test leads in the wrong socket on the tester (especially getting black & green the wrong way round)
- the selector dial not quite clicking in to the intended position so you're not doing the you thought you were

Another possibility is that the fuse in the plug top of the socket test lead has blown - never happened to me but it may be worth checking.

All that said, if the tester is working in one location (at home) then the strange results elsewhere would appear to indicate a fault in the installation rather than the tester.

I would check your neutral continuity in particular, as that is the extra conductor used in no-trip testing.

A quick question - when you say it goes to '55 volts' when doing the rcd test, what do you mean by the rcd test? - the no loop earth loop impedance test for when there's an rcd on the circuit, or the actual test of the rcd itself?

 

[Zorro]

www.pat-services.co.uk/downloads/manuals/299_megger_1500_series_userguide.pdf its always good to read he user guide of any test equipment.

Also doing Zs at lights could be classed as dangerous i.e. working at height the test should be done by calculation Ze + R1+R2=Zs , remember Electricity @ Works 1989 Regulation 14.

 

[badwolf]

Thanks sparkinlee,

Ive had problems with the dial not quite clicking on the required test, but on this occassion it was correctly positioned! I tried the same tests on another installation, in another property, quite near to the job, and got the same problems, it was only when i got home that i tried it again and got reasonable readings.

I was trying to do a rcd test and that was when i found it didnt want to do that either, i had it set on the auto feature, and then change it to manual, but still problemo's. I really dont know cos the meters only a couple of months old.

Before the live tests, i did do full r1+r2 tests, on all circuits, and ring continuity of l,n,e, all of these were fine, so as usuall i proceded with live tests, i did recieve a zs of .12, and i carried out a basic checks to make sure there were nuetrals at the locations that i had checked and had problems with! maybe the meter is running low on batteries, but i thought there would be an indicator of some kind!

 

[tony mc]

Sounds like your on the wrong settings.

When doing loop tests its the green zone on your meter a prior to the tester detecting voltage it will read < 55 v

When doing RCD tests on the blue zone on the meter and set for a 30mA RCD the meter should display < 100 v before detecting voltage.

Also make sure your meter is set for 50v touch voltage and not 25 v

Have a look at you tube and type in Megger 1552 and you have two demos part 1 and part 2 this should help.

Hope this helps.

 

[tony mc]

On the high loop range you do not need a neutral its a two lead test but on the no trip that requires a neutral.!!

 

[badwolf]

Hi Zorro,

I have read and fully understood the manuals thanks, it doesnt highlight this problem however, which is why i thought maybe someone has had a similar experience, but thanks for the link.

Also my niceic inspector doesnt like calculated zs's, has asked me to always measure, there was no safety problem here however though, cos i measured it from a light switch. But thanks for your concern!

 

[tony mc]

Bit stange that as I thought it was NICEIC who were the ones against live ZS testing apart from useing a 1363 plug ,its also in the video re periodics.

 

[badwolf]

thanks Tony

I was using the plug lead, as it was a socket outlet, on the no trip setting and got my strange results, i dont know how i could be on t he wrong setting, cos theres only hi and no trip, and the rcd only has auto or 1x and 5x and ramp. and have checked it is set top 50v touch voltage. I applied the exact same tests at my property and it worked fine, thats whats puzzling me.

 

[badwolf]

the last time i was inspected, he asked me to carry out a ze at the origin and a zs at the pendant, along with dead ir tests on the ring and ring continuity, when i said i could calculate the lighting zs, he said that it wouldnt be correct and that it should always be measured, im against live zs testing unless neccessary which is why i thought it was strange that he would say that!

 

[tony mc]

I would keep a eye on it and when you do the tests you should have a good idea what the results are going to be especially when you have done the dead tests.

The meggers should have a 3 year warranty and if you continue to have trouble get it looked at ASAP.
Make sure the batterys are in good working order when you switch it on it will give you a quick battery voltage displayed on the screen.