RCD auto test function

[graeme210375]

I use a Dilog 9083P MFT, which was recently calibrated.

Have just finished extending a ring circuit at a customers house. All testing OK until i used the 'auto test' function to test the 30mA RCD at 5 x IʌN @ 0º, the trip time showed >40mS. All other tests were within limits (5 x IʌN @ 180º was 19mS)

When I manually selected the individual 5 x IʌN @ 0º setting, the trip time was 23mS.

Tried it again on the auto setting and a reading of >40mS was displayed.

Is there something in an auto test function that could cause this?

I'm aware that there can be an anomaly when performing direct Zs readings on some testers with a 'no trip' function, but are there any similar anomalies on the auto test RCD function?

Many thanks

 

[telectrix]

if you've used the tester plugged into a socket, the results can be affected by the circuit itself. try testing at the RCD with no circuit connected if you get strange readings otherwise.

 

[graeme210375]

if you've used the tester plugged into a socket, the results can be affected by the circuit itself. try testing at the RCD with no circuit connected if you get strange readings otherwise.

Thank you

Heading back tomorrow to finish a couple of other items. I had just used the plug in adapter in a socket. Will re-test at the RCD and see what happens.

 

[Silly Sausage]

Try it out at home, both at the RCD and remotely.
Hopefully it's not your MFT that's faulty.

 

[telectrix]

bit of a pain having to switch RCD back on and keep the probes in contact. another possibility is the MFT warming up during auto test. funny things these modern gadgets can be. i still rely on a 40 year old analogue megger for fault finding.

 

[Engineer54]

bit of a pain having to switch RCD back on and keep the probes in contact. another possibility is the MFT warming up during auto test. funny things these modern gadgets can be. i still rely on a 40 year old analogue megger for fault finding.

Is that a Wind Up?? lol!!

 

[telectrix]

Is that a Wind Up?? lol!!

nah. edgecombe. had to replace the PP7 with 2 PP3 in parallel.

 

[Former Sponsor TM]

Depending on the test equipment, components can sometimes store electrical charge which needs to be discharged when REPEATEDLY testing. Turn the mechanical dial fully clockwise and anti clockwise a few times to discharge components before retesting.

 

[Engineer54]

nah. edgecombe. had to replace the PP7 with 2 PP3 in parallel.

Just having a little quib with you Tel!! lol!!

You'd know this, ....What was that small single voltage Wind Up Megger called? Think it was mini somthing or other...

 

[graeme210375]

Depending on the test equipment, components can sometimes store electrical charge which needs to be discharged when REPEATEDLY testing. Turn the mechanical dial fully clockwise and anti clockwise a few times to discharge components before retesting.

Thank you. I'll give it a try. Unfortunately didn't get a chance to test it at home as a comparison.

 

[telectrix]

Just having a little quib with you Tel!! lol!!

You'd know this, ....What was that small single voltage Wind Up Megger called? Think it was mini somthing or other...

like tis?

EVERSHED & VIGNOLES LTD, MEGGER VINTAGE RED BAKLITE INSULATION TESTER SERIES 3 | eBay

 

[Geordie Spark]

Thank you

Heading back tomorrow to finish a couple of other items. I had just used the plug in adapter in a socket. Will re-test at the RCD and see what happens.

I have never seen the sense in plugging a tester into a socket to test an RCD.

It's the RCD that you're testing so test the RCD at the RCD without other complications getting in the way, then you KNOW you've tested the RCD!

 

[Engineer54]

like tis?

EVERSHED & VIGNOLES LTD, MEGGER VINTAGE RED BAKLITE INSULATION TESTER SERIES 3 | eBay

Maybe, if not very similar. I think the small megger i'm thinking about was called a ''WEE megger'' or something very similar....