MFT shows 235V, Drummond tester says dead, no live present

[The Ghost]

Attended call out at shop. Freezers, chillers and tills were down. Using MFT on V. measurement got 235V plugged into socket. Tested inside socket at terminals with drummond tester, nothing 0 V. Switched MFT to Loop and the neutral was missing. Just a bit puzzled why the MFT shows V. and Drummond 0 V. The neutrals in the neutral block had cooked away, loose neutrals and so on. I would post a pic but the forum does not allow me to post any pics any more.

 

[Strima]

Tester using earth for reference rather than neutral.

 

[The Ghost]

Yes @Strima seems to be the obvious conclusion but one would normally expect it to ref. Neutral so a small caution re using MFT for V. Testing. I will check with the manufacturer regards this interesting finding.

 

[Deleted member 9648]

It's easy to get caught out. Some time back I tested a socket at the terminals with an older 2 probe voltage tester both L-N and L-E. Dead. Disconnected socket and promptly got a handful off the live. Turned out the N had gone missing and the earth had never been connected.
The moral being always follow safe isolation procedure and use an approved 2 probe voltage tester which indicates voltage even if only one conductor is present.

 

[The Ghost]

Just experimenting using linux to upload pictures which seems to work. This is a picture of the burnt neutrals etc.

 

[Lucien Nunes]

Never assume! Check the instructions for your particular MFT as the voltage measurement strategy varies between models. E.g. I think the Megger 1500 displays the L-E voltage by default, while the 1700 series displays the highest voltage present between any pair of leads if all are connected. So could display L-E or L-N, or even N-E if L is missing.

 

[KEV 1 N]

Some times my MFT, when set to test Zs , will show no volts, yet I know there there is power there.
I switch the MFT off then on again, re-test and then it reads the voltage. I wouldn’t be trusting a MFT to verify if a circuit is live or dead.

 

[buzzlightyear]

I switch the MFT off then on again, re-test and then it reads the voltage. I wouldn’t be trusting a MFT to verify if a circuit is live or dead

so the voltage indicator is not needed then ,you better tell the manufactures then .is like asking for a pizza with out the cheese .

 

[Rpa07]

Just experimenting using linux to upload pictures which seems to work. This is a picture of the burnt neutrals etc.

View attachment 41960

Indiana Jones wouldn’t have liked that!

I wouldn’t trust anything but a voltage indicator before sticking my hands where they shouldn’t be!

 

[The Ghost]

Just so you know guys...I would not even stick your hands where they shouldn't be without using a BS61010 BS EN 61243-3 GS38 approved two pole voltage tester so please try not to worry about me using the wrong equipment for the job but thanks for your concern in any event. I was merely highlighting the caution regards why not to use MFT (Which we all know we should not) I think as @buzzlightyear said the voltage indicator is not needed as it is may be dangerous not just undesirable.

 

[KEV 1 N]

The voltage indicator setting is sometimes useful for say measuring voltage present at various points for volt drop etc

 

[The Ghost]

Looking at my Kewtech 65DL to test for voltage you must use the L and PE terminal for the leads, not the neutral. But what was useful using the three lead plug top lead, is it showed the missing neutral. So I knew where to look for the problem or took a well educated guess I should say.

 

[The Ghost]

Zoomed out pic of the offending CU. New box recommended.

 

[Gavin John Hyde]

@Vortigern if you want to query tech stuff with kewtech the man to ring is alan towler, hes the tech support guy, very helpful and normally has the answers. his info is on the kewtech site but save you having to go on to it, his number is 07970826188.

 

[sparkdog]

I think the MFT would have a high impedance on volts , so would only need a tiny bit of current to give a reading.