voltage tester show sequence of lights.

[Mike63]

After some advice please, I`m gas safe registered and have to do safe isolation to TB118. It`s a new build site and the fast blow fuses were blowing on the boiler; the spark said it was a problem with the boiler. Put a temp on the boiler and it works. On doing a dead test on earth to live on the supply, I`ve got a Di-Log 6780-volt tester the red AC and green L light up, I`ve not come across this before and with the fuses blowing on the boiler I would expect the continuity to light up.
I`d like to know the reason for this so that I can look out for it in future, Thanks for any help.

 

[Electro-tech]

I'm no expert as I do not own this model but probably similar to my Fluke. For the AC light, I guess you must be picking up voltage this will illuminate for AC or DC volts, Maybe just to warn you that there is very low voltage present below 12 volts. Did you try reversing the probes ? The L would be indicating AC single-phase voltage. If DC voltageI guess it would show as polarity + or -.

 

[Vortigern]

If you test live to earth you will get a live reading in any event. I imagine you have a TN- system so neutral and earth are connected at the incomer/cut-out so you will make a circuit the same as the L-N test.

 

[Mike63]

Thanks for the replies, the electrician removed the lives from the RCD, and I was getting the same reading at the board L to E, but I recall that there were 2 lives which to me is indicating a ring circuit and the heating is supposed to be on its own supply. I`ll check on Monday, if it`s not been fixed.
It`s what`s causing light sequence if there is no power to the circuit, that i don`t understand.

 

[davesparks]

I use a di-log voltage tester as my main safe-isolation tester.

The single red and single green LED will illuminate in the presence of a phantom/ghost voltage.
If an actual voltage is present you will see the relevant red voltage level LEDs.

The continuity function has a threshold of 2Kohms so any impedance greater than this will not illuminate the yellow LED.

 

[Mike63]

According to the spark, the fault is on the neutral, still don't understand why both fast blow fuses would blow on the boiler.
Thanks for your replies.