Fluke T100 Voltage/Continuity tester

TTbangbang · Oct 21, 2008

Hello,

I have one of these testers and whilst testing between phase and neutral at a ceiling rose on a supposedly dead lighting circuit (mcb off, and light switch already tested as dead), the LED for single pole phase test came on. There was no voltage display indication. As I was unsure what this SP phase indication meant, I isolated the whole installation before removing the ceiling rose.

...Grandpa and grandma huffily walked off into the sitting room with candles.. but I digress...

Please could you advise on what exactly is a single pole phase test, how it should be tested for (where to stick the probes), and why did it give a positive result on an isolated circuit? Thank you.

Mr Sworld · Oct 22, 2008

There can be a voltage present on the neutral even when the live is isolated, this can be due to inductance or a multitude of other causes.

When a live is isolated it doesn't 'isolate' the circuit, you would need to pull the neutral to completely isolate a circuit. Hence double pole switches.

Say what you like about our European cousins electrical work but when I was over in France doing a bit of work I noticed all their fuses/mcb's are double pole so when you pull/switch off one of the the circuit IS isolated. A good idea I think.

TTbangbang · Oct 22, 2008

Thanks for that

I agree about DP mcbs being a good thing (especially in the DB I've inherited - I'll put a picture up soon - the neutral isn't isolated by the main switch..). Tis a great shame the DP rcbos are prohibitively expensive

Bclearnersparks · Oct 28, 2008

Sorry its a week later, but I have had same problem when i purchased T100.

It was quite a while ago but I think I was connecting up new cooker, switched off breaker but got voltage on tester when checking isolation on cooker outlet plate as no ccu fitted. Being paranoid i got multimeter out and found about 6volts present at terminals.

Switched off main breaker and voltage back to 0v.