Hi, i have just had boiler serviced by gas fitter. as part of inspection, he tested two plug sockets at different ends of the house and said resistance in earth was too high. Around 200 mark. What does this mean? what is worst case scenario and likely causes of this problem. Panicking a bit.
high resistance and earth wire - what does it mean??
- Thread starter jje1973
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Sounds like he as conducted an Earth Fault Loop Impedance test on the ring main to check that it complys with Regulations (its likely that he spurred off the ring to supply the boiler) if he is reading was 200ohms than thats absolutly massive and needs immidiate attention but to be honest I doubt that he would have got a reading at all if the EFLI was that high .A correct EFLI for a ring main should be below 1.2ohms
phone him up and ask for a more details of what test he did and ask him to double check the result 200 is way too high
phone him up and ask for a more details of what test he did and ask him to double check the result 200 is way too high
if you have a TT earth (earth rod, rather than earth supplied by supplier) then i think 200ohms is about on the borderline (i think 200 is the borderline and companies recommend <100 on installation but Im not sure), because the ELFI is so high on TT's all the electrics should be through an RCD as the MCB's wont disconnect quick enough on an earth fault.
do you have an earth rod? (most people dont, most earths are from the supplier because its more reliable) if you dont know look at these pictures from the wiki and tell us which one yours looks like (or even better post a picture of your incommer/meter/fusebox area
do you have an earth rod? (most people dont, most earths are from the supplier because its more reliable) if you dont know look at these pictures from the wiki and tell us which one yours looks like (or even better post a picture of your incommer/meter/fusebox area
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200 is the limit above which the OSG advise investigation.
100 is the limit set by NICEIC.
If your supply comes from overhead (sometime underground), then it will have no earth connection with it. This is provided by the consumer,usually through an earth rod.
If yours in underground, if there is no connection to the sheath for an earthing terminal, then it is subterranean TT.
In this case, you need overall protection by a 100mA S type RCD plus further 30mA G type RCD protection for socket outlets.
If you have TT and no RCD's, you are AT RISK!!
However, if you have the RCD set-up as described, 200 Ohms is acceptable, as long as it is no more.
Best solution is to ask the DNO to PME your supply to bring the EFLI right down. Costs up to 100 quid.
100 is the limit set by NICEIC.
If your supply comes from overhead (sometime underground), then it will have no earth connection with it. This is provided by the consumer,usually through an earth rod.
If yours in underground, if there is no connection to the sheath for an earthing terminal, then it is subterranean TT.
In this case, you need overall protection by a 100mA S type RCD plus further 30mA G type RCD protection for socket outlets.
If you have TT and no RCD's, you are AT RISK!!
However, if you have the RCD set-up as described, 200 Ohms is acceptable, as long as it is no more.
Best solution is to ask the DNO to PME your supply to bring the EFLI right down. Costs up to 100 quid.
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