Damn this heat. I just can't think straight!
Been called to an installation where the ceiling was sparking near a light. All the lights were working ok. The spark was coming from a loose earth wire from the light fitting which was touching a metal ceiling frame. I checked the light switches and found a facia screw piercing the neutrals at the back of the knockout box. I figured that could be it so I fixed the damage to the neutrals and reenergised the circuit only to find none of the lights worked! Checked all the connections and seemed to get 209v from one of the neutrals. At this point everyone was going home (office) and I said I'd return when I can isolate the ccu to do proper testing on the circuit.
Now, my hot sweaty thoughts are the polarity has been crossed over somewhere and for the last god knows how long the cpc has been used as the neutral through this screw through it. Does that sound plausible?? And if so what is the quickest route to narrowing down where the reverse polarity is? There are some junction boxes high above the false ceiling which require scaffolding to reach so if I can avoid that... Or, more likely would you not agree, that the neutral is just disconnected at the ccu (or elsewhere)? But then would i have voltage at one point of it??? Arhhh. Wish it would rain soon so i can think again!! Beer time
Been called to an installation where the ceiling was sparking near a light. All the lights were working ok. The spark was coming from a loose earth wire from the light fitting which was touching a metal ceiling frame. I checked the light switches and found a facia screw piercing the neutrals at the back of the knockout box. I figured that could be it so I fixed the damage to the neutrals and reenergised the circuit only to find none of the lights worked! Checked all the connections and seemed to get 209v from one of the neutrals. At this point everyone was going home (office) and I said I'd return when I can isolate the ccu to do proper testing on the circuit.
Now, my hot sweaty thoughts are the polarity has been crossed over somewhere and for the last god knows how long the cpc has been used as the neutral through this screw through it. Does that sound plausible?? And if so what is the quickest route to narrowing down where the reverse polarity is? There are some junction boxes high above the false ceiling which require scaffolding to reach so if I can avoid that... Or, more likely would you not agree, that the neutral is just disconnected at the ccu (or elsewhere)? But then would i have voltage at one point of it??? Arhhh. Wish it would rain soon so i can think again!! Beer time
