Good evening all,
I’m currently working on a domestic new build, it’s a TT system with the meter, Time Delay RCD and Fused isolator installed within a road side GRP kiosk. From the kiosk there is a 50.0mm 3 Core SWA (approx 45mtr run) which terminates into a Sarel enclosure externally and then short DI tails to the DB (split/split) internally. Due to the number of additions a second DB was required which is fed from the first (approx 5mtrs of 10.0mm twin and earth). After testing/livening up the sub-main to the second DB yesterday I used my Fluke (T5-1000) tester as a double check that polarity etc was all ok .... L-N 235V, L-E 234V, N-E 0V .... I have absolutely no idea why I did this next step, but I did, and this is the cause of my confusion. With the main switch on the second DB in the off position I tested between the incoming live and the neutral bar ... 208V, the main switch is definitely double pole and operating correctly so in my head I initially thought that maybe I had a neutral pinched to earth somewhere .... but it was time to go home so I just disconnected the supply to the second DB. Returned to site today, re-tested the five circuits from the second DB, all good ... with the main switch turned off I used the Fluke to measure between the incoming live and each neutral individually, the three circuits that are local to the DB all 0V, the two circuits that leave the room 72V on one, 150V on the other (yet these two circuits have now been tested twice and additionally the cables traced through their entire routes). I then went to the first DB .... (only one circuit connected to one side of the split board, the supply to the second DB), turned off main switch, measured between live incomer and neutral bars 0V on the one with nothing connected, 208V on the one with the neutral to the other DB ... retested the sub-main to second DB ... all fine !!! I’m getting frustrated again just writing this down, anyone experienced similar or have any suggestions please?
