Social Housing EICR Contract

1st question - If your R1 + R2 value is lower than either your RN or your R1 continuity tests - What would that tell you and what would you do to prove the circuit is ok for continued use in its current state?

R2 cound be very low, and no fault, the classic is a return via  plumbing from a water heater, but there are other similar cases.

On a ring main, the two halves of the ring main (at the far point on the ring) appear in parallel.

If you want a test to make some sense of this, measure as 2 spurs separately (by breaking the ring and testing call it  the Left hand pair only, and measuring L-E  to the dis board, then changing the short to the right hand L-E pair) you must combine the results (using the parallel R formula.) This also allows you to see how far round the ring you really are, and that you are not in the middle of a spur which may not be obvious on inspection on an unknown circuit.

2nd question - If you had either excessively high, or no continuity on R1, RN or R2 end to end readings, how can you quickly and simply prove the circuit is still safe for use without getting deep in to further investigation?

If it is a Radial, you cannot, it i broken. If it is a ring,  it may be 'crab claws' and still have power and earth to every point. It is not nice, but it is possible to drop the breaker to 20A and make it a centre fed radial. But if there is ring-round on 2 out of 3,  say L and N but not E or similar, then it is a dead cert that something nasty has happened.

3th question - When doing an I.R test whereby........ line+neutral are connected together and tested to earth - Is there any electronic or electrical device which, if connected, could result in a test failing the circuit? I had one today 0.79 ohms

If it really is 079 ohms, that is comparable to the R1 R2 etc and represents a dead short, The only electronics that will do that is faulty.

If it is really much higher but that is what your meter says, then I'd be looking for leakage to TV antennas and other cables that leave the building. If it is  whole building L+N to E and the building has a lot of kit in, 0.79 meg may be OK.

If you to L+N to CPC lifted,  and compare with L+N to CPC + MET + Bonding   you will be able to see if the leakage is to the CPC, or to an external thing, or both.

Also repeat at 120 or 250V test voltage, if the value is much higher at lower voltage is electronics or a neon.

1st question - If your R1 + R2 value is lower than either your RN or your R1 continuity tests - What would that tell you and what would you do to prove the circuit is ok for continued use in its current state?

R2 cound be very low, and no fault, the classic is a return via  plumbing from a water heater, but there are other similar cases.

On a ring main, the two halves of the ring main (at the far point on the ring) appear in parallel.

If you want a test to make some sense of this, measure as 2 spurs separately (by breaking the ring and testing call it  the Left hand pair only, and measuring L-E  to the dis board, then changing the short to the right hand L-E pair) you must combine the results (using the parallel R formula.) This also allows you to see how far round the ring you really are, and that you are not in the middle of a spur which may not be obvious on inspection on an unknown circuit.

2nd question - If you had either excessively high, or no continuity on R1, RN or R2 end to end readings, how can you quickly and simply prove the circuit is still safe for use without getting deep in to further investigation?

If it is a Radial, you cannot, it i broken. If it is a ring,  it may be 'crab claws' and still have power and earth to every point. It is not nice, but it is possible to drop the breaker to 20A and make it a centre fed radial. But if there is ring-round on 2 out of 3,  say L and N but not E or similar, then it is a dead cert that something nasty has happened.

3th question - When doing an I.R test whereby........ line+neutral are connected together and tested to earth - Is there any electronic or electrical device which, if connected, could result in a test failing the circuit? I had one today 0.79 ohms

If it really is 079 ohms, that is comparable to the R1 R2 etc and represents a dead short, The only electronics that will do that is faulty.

If it is really much higher but that is what your meter says, then I'd be looking for leakage to TV antennas and other cables that leave the building. If it is  whole building L+N to E and the building has a lot of kit in, 0.79 meg may be OK.

If you to L+N to CPC lifted,  and compare with L+N to CPC + MET + Bonding   you will be able to see if the leakage is to the CPC, or to an external thing, or both.

Also repeat at 120 or 250V test voltage, if the value is much higher at lower voltage is electronics or a neon.