Higher rn than r1

[Dartlec]

Where is the point at which a higher (but continuous) conductor reading should be considered 'OK' on an EICR?

I know the theory is that it should be between 0.05 ohms, but when it falls outside that, how do others decide when it becomes an issue that must be resolved?

Checking a small flat today, with a single socket circuit - about 14 sockets in total.

r1: 0.7 Rn: 0.84 r2: 1.17

Of course the ideal answer would be to drop every socket and check connections etc...and perhaps do an r1+rn at every socket to try to isolate the issue. This flat is empty so it's probably doable, but in a normal inhabited home it becomes trickier...

Not to mention that unless you FI and then quote for the work you risk not doing much...

The same applies to cpcs where the reading is higher than it should be, but still continuous (And not just because it's 2.5/1.0 cable)...

Is there a rule of thumb people have for when they would accept it without comment, note it but not code it, or FI/C2 it?

 

[Pretty Mouth]

Where is the point at which a higher (but continuous) conductor reading should be considered 'OK' on an EICR?

I know the theory is that it should be between 0.05 ohms, but when it falls outside that, how do others decide when it becomes an issue that must be resolved?

Checking a small flat today, with a single socket circuit - about 14 sockets in total.

r1: 0.7 Rn: 0.84 r2: 1.17

Of course the ideal answer would be to drop every socket and check connections etc...and perhaps do an r1+rn at every socket to try to isolate the issue. This flat is empty so it's probably doable, but in a normal inhabited home it becomes trickier...

Not to mention that unless you FI and then quote for the work you risk not doing much...

The same applies to cpcs where the reading is higher than it should be, but still continuous (And not just because it's 2.5/1.0 cable)...

Is there a rule of thumb people have for when they would accept it without comment, note it but not code it, or FI/C2 it?

I would use 0.05 ohms as the threshold, any higher than this would be a C2. Not a FI IMO - we can be fairly certain that, in this case, it's a loose connection which won't get better on it's own.

To fault find, I would link L+N+E on one leg only at the board, and test and record continuity of L-E, and N-E at each socket, using a socket adaptor. The L-E reading is your reference, it will tell you the position of the socket relative to the start of the leg. The N-E reading should be identical to the L-E reading up until the point of the loose connection, after which it will be higher.

This way, you can fairly quickly narrow it down to 2 sockets before having to remove any.

 

[littlespark]

Look for an obvious changed socket..... new white, or decorative. Probably done by homeowner in the past and maybe not correctly.
Educated guesswork.

Could be a spur joint box under the floor though.

 

[GBDamo]

An absolute figure is hard to apply as it all depends on the size of a circuit.

Without the original EIC, you have no baseline, all three readings could be high.

Maybe a percentage of the difference between the lowest and highest?

The smallest ring I ever saw was immeasurable as the single socket it fed was right next to the CU.

Could only imagine the spark responsible had only a 32A RCBO left?

 

[SJD]

The smallest ring I ever saw was immeasurable as the single socket it fed was right next to the CU.

Could only imagine the spark responsible had only a 32A RCBO left?

But the socket could have been a spur at the origin (with the actual ring missing)!

 

[GBDamo]

But the socket could have been a spur at the origin (with the actual ring missing)!

It could have been, off any of the other three rings, some people don't like doing that though.

 

[SJD]

If you've narrowed it down to a couple of sockets or area of the house, sometimes wiggling a plug in each suspect socket while measuring rN can give it away, as rN jumps about. Not the most scientific, but I've done this successfully when the socket are difficult to remove, e.g. grouted in or minimal access.

 

[Pretty Mouth]

Without the original EIC, you have no baseline, all three readings could be high.

Possible, but in this case unlikely, as the r1 and r2 results are in the correct proportion for 2.5mm T+E with a 1.5mm CPC