Hi, while carrying out an EICR at a farm cottage on Friday i came up against a problem early on. Whilst measuring the Ze the reading i obtained was 0.97 Ohms and 27Amps Pfc.
Now the earthing system itself is quite strange. Next to the consumer unit is an old service head holding a 60A BS 88 fuse. Terminated into this is a 16mm split concentric. The live is connected into the service head and the neutrals go into a henley block. This block is where the 16mm earth going into the consumer unit is connected. The earths of the split concentric are cut off where cable is stripped for termination into the service head.
Things now get interesting.
Outside there is a meter box that the split concentric goes back to. This meter box is supplied by a 16mm 3 core SWA that travels 300+ yards underground from a new box on the edge of a field that was fitted by the SSE last year when new overheads were run to the farm.
This 16mm SWA supplies TWO! cottages. The brown core is the Live for the cottage i was in, the Black is the Live for a cottage next door and the Grey is the Neutral. The sheath of the SWA is the earth. The cores of the SWA go into blocks where they are split and each is then terminated into a switched fused isolator serving the split concentric feed to each cottage. The earths that were cut off at the service head inside the cottage - at this end are connected to the earthing terminal of the switch fuse isolator.
The readings in the cottage for the EICR were generally all ok and under the max Zs value however one ring circuit was measuring at 1.55 ohms. I imagine i could change the RCBO serving this circuit from a 32A to a 20A.
Does anyone know of what should be done here regarding the Ze exceeding the max value? Somewhat in disbelief that two cottages are supplied such a distance with a cable so small!
Thanks
Now the earthing system itself is quite strange. Next to the consumer unit is an old service head holding a 60A BS 88 fuse. Terminated into this is a 16mm split concentric. The live is connected into the service head and the neutrals go into a henley block. This block is where the 16mm earth going into the consumer unit is connected. The earths of the split concentric are cut off where cable is stripped for termination into the service head.
Things now get interesting.
Outside there is a meter box that the split concentric goes back to. This meter box is supplied by a 16mm 3 core SWA that travels 300+ yards underground from a new box on the edge of a field that was fitted by the SSE last year when new overheads were run to the farm.
This 16mm SWA supplies TWO! cottages. The brown core is the Live for the cottage i was in, the Black is the Live for a cottage next door and the Grey is the Neutral. The sheath of the SWA is the earth. The cores of the SWA go into blocks where they are split and each is then terminated into a switched fused isolator serving the split concentric feed to each cottage. The earths that were cut off at the service head inside the cottage - at this end are connected to the earthing terminal of the switch fuse isolator.
The readings in the cottage for the EICR were generally all ok and under the max Zs value however one ring circuit was measuring at 1.55 ohms. I imagine i could change the RCBO serving this circuit from a 32A to a 20A.
Does anyone know of what should be done here regarding the Ze exceeding the max value? Somewhat in disbelief that two cottages are supplied such a distance with a cable so small!
Thanks
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