How do most of you prefer to do EFLI tests?

[telectrix]

it's not always the tester at fault. sometimes you can get vastly differing readings on either side of an RCD. if in doubt, i take a reading from the L busbar. it should be close to the Ze value (allowing for parallel paths).

 

[Guitarist]

it's not always the tester at fault. sometimes you can get vastly differing readings on either side of an RCD. if in doubt, i take a reading from the L busbar. it should be close to the Ze value (allowing for parallel paths).

Just tried that tel. 0.21 Ze on high current setting, 0.55 Ze on no-trip. 0.71 on no-trip at busbar....

 

[ackbarthestar]

Just tried that tel. 0.21 Ze on high current setting, 0.55 Ze on no-trip. 0.71 on no-trip at busbar....

Interesting....
So which answer would you say was the most accurate?

 

[Guitarist]

Interesting....
So which answer would you say was the most accurate?

Well, when I did exactly the same thing last week I got - 0.21 Ze on high current setting, 0.23 on no-trip setting and 0.26 on no-trip at both busbars (split-board). Hadn't thought to try all 3 again until tel suggested it. My assumption is that the meter has had a nervous breakdown from all this testing....

 

[ackbarthestar]

I personally think that if you haven't used your instrument as a 'battering ram' then its likely to be the condition of the supply, filtering and switching harmonics.
Things I might consider would be the time of day when the tests were done, what about local industry ? etc etc

Megger do recognize that inaccuracies in readings due to anomalies in the supply.

Having said that, I get odd results from time to time when doing loop testing using the non-trip function

 

[Sav]

By measurement. I would check your original result by linking out the rcd, the no-trip test seems to give funny measurements sometimes.

Hi Truckster,
Can you just explain how to link out the RCD please.
Ive never used this method, but I too have sometimes experienced higher Zs results when using the no trip function on my megger 1553.
Thanks for your help,
Sav

 

[Guitarist]

I do recognise that the readings will change slightly depending on conditions. I also recognise that 15mA will not push through in the same way that a few Amps will. All that said, it is pretty pointless paying all this money for a piece of kit if most of the time the readings are not worth toffee....
I'm hoping it is simply a faulty meter and my faith in Megger can be restored.

 

[ackbarthestar]

Well, if you think that the instruments were designed to provide readings using sinewave power signals. The supply waveform has changed but the instrument electronics appear have not.
I think there at least two methods of measurement.
1/ limiting the flow through the instrument to 15mA,
2/ Flooding the magnetic core of the RCD with DC current and then allowing a couple of cycles of something in the region of 10A to flow.

Megger recommend that Zs measurements are done at least three times and the average reading taken.

As far as linking out RCDs while taking Zs readings. This is strongly not advised by all concerned with I&T. However, I used to do it before DLOCK , with a LT5.

 

[truckster]

Hi Truckster,
Can you just explain how to link out the RCD please.
Ive never used this method, but I too have sometimes experienced higher Zs results when using the no trip function on my megger 1553.
Thanks for your help,
Sav

I link from the top of the RCD to the bottom with a couple of short 6mm links. As Ackbarthestar says it's not a recommended method with the advent of d-lock but sometimes it's the only way to get a reading. D-loc doesn't always work and the rcd trips so out come the links.

Do it at your own risk and recognise the dangers from doing so!

 

[tony mc]

When I have encountered High readings on a No trip I do it another way.

Isolate the circuit and then link line and earth at the end of the cct or somewhere on the ring if a ring ! (I have a plug made up for this)

At the CU test between the incoming Live and the isolated cct !

Remember to remove your line cpc link prior to switching the cct back on!

 

[Guitarist]

Hard to link out the RCD's with a Starbreaker unit....

 

[Sav]

Thanks for the advice truckster,
I will avoid that may be and just do what Ackbarthestar said, to do the measurement 3 times and take the average.

Im thinking of whether to buy a Fluke, but Im so used to the Megger !!!

Sav

 

[truckster]

Hard to link out the RCD's with a Starbreaker unit....

Very true

 

[SPARTYKUS]

Just get a 1552.

 

[Cygnet]

I have experienced spurious readings with my MFT 1730 on the L-PE range, and know of two or three other testers who have experienced the same problem. I have made enquiries and Megger have been having issues with their software, hopefully this will be resolved when the instrument is returned for calibration.
I have also had problems with the Metrel MI 3125 on the not trip test where the screen goes blank and then returns to the start screen, i have returned them and the MI3122 RCD / ELI as well, to the manufactures but the problem has reoccurred so this along with the rechargeable batteries not retaining charge during cold weather to do a days testing, I have stopped purchasing the Metrels and reverted back to Megger.