Guys,
Found a strange one today wondered if anyone else had ever experienced iy.
Changed a consumer unit uder a stair cupboard which had been virtually kicked off the wall. Typical 3 bed semi house. During dead testing R!+R2 of downstairs lighting i found something which shows the importance of testing at every light and switch for the maximum r1r2.
The house lighting was not wired in a loop circuit and only one cable was at each rose. In the kitchen a fluorescent had an extra single core neutral cable black with grey sheath connected to it. Ihad megged the installation and the downstairs lighting measured >299 between PN and PN E. The loop impedance and r1 r2 measured ok. Found the upstairs landing 2 way from downstairs hall to be maximum zs of 1.2. everything seemed fine. Still wasnt happy with what looked like a borrowed neutral so traced it after ripping boards up. They had wired the two way switch for the landing light fed via the hall 2gang switch as normal but instead of taking a neutral to a jb then light they only had the switch live going to it via the hall landing 2 way switch and pinched a neutral from the kitchen in a single core. Problem was i knew something was up so i split the neutrals in the kitchen. FOUND 230V on the single core neutral. Isolated it and megged it again but read ok to phase >299. Luckily the leakage was coming from a cable on that circuit because when i isolated the downstairs lighting the fault voltage went. Tried a phase neutral loop on the correct neutral at the kitchen light and got 0.45, seemed ok. Megged the single core rogue neutral to phase and got 100 ohms.. This is why the breaker wasnt tripping. High reistance phase leakage.Ripped the loft to bits couldnt find it. Baffled. Then i realised tie backs for the curtains Landing window were screwed and plugged, the t**t was through the single core and a seperate twin and earth. What a nightmare. Provessometimes testing isnt always failsafe. Ironic part is this circuit megged >299 the satisfactory upstairs lights measured 2.22M only, big drop from 299 which all the other circuits are. What a day......
Found a strange one today wondered if anyone else had ever experienced iy.
Changed a consumer unit uder a stair cupboard which had been virtually kicked off the wall. Typical 3 bed semi house. During dead testing R!+R2 of downstairs lighting i found something which shows the importance of testing at every light and switch for the maximum r1r2.
The house lighting was not wired in a loop circuit and only one cable was at each rose. In the kitchen a fluorescent had an extra single core neutral cable black with grey sheath connected to it. Ihad megged the installation and the downstairs lighting measured >299 between PN and PN E. The loop impedance and r1 r2 measured ok. Found the upstairs landing 2 way from downstairs hall to be maximum zs of 1.2. everything seemed fine. Still wasnt happy with what looked like a borrowed neutral so traced it after ripping boards up. They had wired the two way switch for the landing light fed via the hall 2gang switch as normal but instead of taking a neutral to a jb then light they only had the switch live going to it via the hall landing 2 way switch and pinched a neutral from the kitchen in a single core. Problem was i knew something was up so i split the neutrals in the kitchen. FOUND 230V on the single core neutral. Isolated it and megged it again but read ok to phase >299. Luckily the leakage was coming from a cable on that circuit because when i isolated the downstairs lighting the fault voltage went. Tried a phase neutral loop on the correct neutral at the kitchen light and got 0.45, seemed ok. Megged the single core rogue neutral to phase and got 100 ohms.. This is why the breaker wasnt tripping. High reistance phase leakage.Ripped the loft to bits couldnt find it. Baffled. Then i realised tie backs for the curtains Landing window were screwed and plugged, the t**t was through the single core and a seperate twin and earth. What a nightmare. Provessometimes testing isnt always failsafe. Ironic part is this circuit megged >299 the satisfactory upstairs lights measured 2.22M only, big drop from 299 which all the other circuits are. What a day......
