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55v between live and neutral
Former Community Member
Question I've got a 4 core hi tuff/ NYY-J cable 230v supply feeding a oil burner and 2 motorised pumps. 2 cores are lives 1 neutral and 1 earth 1 of the pumps burnt out and was replaced when checking the voltage at the switches 1 core is 230v live to neutral and live to earth as expected on the other core live to neutral I'm getting 55v and same for live to earth. Any suggestions on where too start fault finding?
Are you using a digital voltmeter? If so you might just be seeing capacitive coupling between cores - i.e. an unconnected core is acting like one plate of a capacitor with another line conductor acting as the other plate. Your voltmeter is then completing the circuit and becomes part of a potential divider with the impedance of the "capacitor" (1/2πFC) on one side and the impedance of the meter itself on the other. It's quite a common effect - in another incarnation it can cause low energy lamps to flicker or gently glow when switched off.
On the other hand you might have some damaged insulation - so do proceed with caution - just in case.
Is the 55 volt wire connected via its own fuse to the supply? If you had a motor burn out could it be that it blew a fuse on that live core. I agree that the voltage you are seeing is probably from capacitive coupling
I suggest a supply-side fuse has blown or one of the switch contacts is open circuit. if the 55V can be discounted as pick up, and I agree it probably can (or leaking round from the other live) then really you have supply off.
Chase further back to the thing supplying it to the point where the two lives part company, assuming thta is at 240 or so then chase in the normal way , or if the route is long with lots of access points, then open one in the middle and decide if the fault is in the 1st half or the 2nd half, and do divide and conquer that way. Given the coupling, de-energise both sides before doing any resistance checks, even just continuity buzzer many not appreciate partial mains, and there is a small risk of the mains coming back on suddenly in response to scratching about, if there it a part burnt contact.
