Megger 1730 MFT. Not tripping on any RCD tests on known good circuit.

[Marti]

G'd Evening Lads an' Lasses,
I've got a Megger 1730 MFT; lovely bit of kit normally. Ex-demo - not had a hard life and was calibrated about eight weeks ago. I normally run it over a Cal-Card and a captive test RCD about once a month and this time it failed to trip the 30ma RCD on 1x, 5x and ramp. Tested all the RCD's in the house - same result. Reset everything to default - same result.

Has anyone seen anything like this? Really appreciate your thoughts. just started out on my own so the timing is ERR...unfortunate if it's terminal.

 

[Sintra]

Was it definitely set for a 30mA test and not 300mA.

 

[Leesparkykent]

G'd Evening Lads an' Lasses,
I've got a Megger 1730 MFT; lovely bit of kit normally. Ex-demo - not had a hard life and was calibrated about eight weeks ago. I normally run it over a Cal-Card and a captive test RCD about once a month and this time it failed to trip the 30ma RCD on 1x, 5x and ramp. Tested all the RCD's in the house - same result. Reset everything to default - same result.

Has anyone seen anything like this? Really appreciate your thoughts. just started out on my own so the timing is ERR...unfortunate if it's terminal.

Send it to these guys Services - https://www.alpha-electronics.com/services/most of their team are ex Megger as only down the road.

 

[SparkyChick]

Given it relies on a connection to earth, I might be inclined to quickly check your earthing. Do a quick Zdb and make sure it's fine.

And it's no good saying the test buttons on the RCDs work because they create an imbalance in a different manner.

 

[123]

Was it definitely set for a 30mA test and not 300mA.

Surely if set for 300mA test on a 30mA RCD it would be more likelyt o trip it?

 

[Octopus]

Can you try it on a mates house? ....

 

[Sintra]

Surely if set for 300mA test on a 30mA RCD it would be more likelyt o trip it?

True. That’s me jumping in again without thinking properly.

 

[Midwest]

Did you do IR tests; had a neutral-earth fault thats stopped an RCD test before.

 

[SparkyChick]

True. That’s me jumping in again without thinking properly.

Chat of ban hammers and WD40 will do that

 

[Marti]

Oh, sorry should have mentioned the obvious. Tested the same with the Megger leads in a breakout and the 1363 plug lead. Both could be faulty but unlikely. Also, when my test RCD failed I used it on all the house circuits but the timer just keeps counting up and eventually display "greater than 40ms". My workshop is TT with a Ze of 75-80 ohms. The house is standard TNC-S. All tested about six weeks ago.

Thanks for all the input people

 

[MFS Electrical]

Had a similar issue when one of my 1720 models went for calibration I’m not sure what they do to it but it worked for one Zs test and then when I switched to do an RCD test I got nada being a curious guy I thought I’d have a look inside I wouldn’t recommend it but that particular meter owed me nothing anyway a bit of solder has melted and a wire jumper had become detached resoldered and checked it - it worked fine so sent it back for recalibration and it was all good if anything the tolerance was slightly better than when compared to the previous cal sheet. Opening the thing was a bugger though that’s why I wouldn’t recommend it it could be very very easy to ruin it...

 

[static zap]

Was it definitely set for a 30mA test and not 300mA.

You may have been wrong , but Operator error (Brain fart) is always possible , the more sure you are of your self .
- Once you remember the wrong way .. Or have mft remember it for you
( miss some obscure setting again) again .. a .. a .. !

 

[HappyHippyDad]

Are you sure you've put the leads into the live and earth into the megger, not the live and neutral. I'm sure you wont have done as it sounds like you've had it for ages but worth saying.
I've only had my megger a short while and I did that by accident and thought.... arghh the RCD's not tripping!

 

[Marti]

Update on the poorly Megger.
Took it into Barking and Dagenham College (did my C&G there) They tested my MFT and leads on a college rig with a known good 1720. Definitely a faulty unit. The only question is whether I caused this switching between functions whilst powered? Don't know but probably worth bearing in mind. Thanks for all the input guys.

 

[Pete999]

G'd Evening Lads an' Lasses,
I've got a Megger 1730 MFT; lovely bit of kit normally. Ex-demo - not had a hard life and was calibrated about eight weeks ago. I normally run it over a Cal-Card and a captive test RCD about once a month and this time it failed to trip the 30ma RCD on 1x, 5x and ramp. Tested all the RCD's in the house - same result. Reset everything to default - same result.

Has anyone seen anything like this? Really appreciate your thoughts. just started out on my own so the timing is ERR...unfortunate if it's terminal.

Are you testing the RCD at the RCD OR via a socket outlet?