Social Housing EICR Contract

AJJewsbury:

If we looking at the best you can do in 1.5 hours then....

I'd forget the R1+R2 tests on radials - they're primarily there to ensure the circuit is safe to energise - but your circuits are already energised - so just do Zs tests - at the very least at each end point (of which there could be more than one per circuit if things branch). There's also a safety advantage in not dismantling things in order to test them (and so re-assembling them after the test, which the consequence that what's put into service isn't quite what was tested). Comparing readings with Zdb should give you an idea if anything is out of the ordinary (although the difference shouldn't really be taken to be a R1+R2 value). Don't forget doing a 'long lead' R1 test if that would be a more convenient way of checking c.p.c. continuity and give an indication of likely Zs. Say if you do a Zs loop test at a ceiling rose (to SL rarther than the loop terminal) and a long lead R1 test to the corresponding switch fixing screws (either from the MET or from the PE terminal in the ceiling rose) and Zs plus you R1 results is still lower than the max permitted Zs, they you can be pretty confident that Zs inside the switch is going to be absolutely fine. There's no need to enter a R1+R2 value on the form if you've already proved c.p.c. continuity and overall Zs by other means.

Continuity on rings I probably wouldn't skip - but if the CU is a mess then do it at a convenient double socket instead as that's likely to be a lot quicker and easier. Parallel paths to the c.p.c. often give Zs or R1+R2 values lower than expected from r1, r2 and rn values - you can't really deduce anything from that fact alone. Different cable types (e.g. one section in 4mm2 rather than 2.5mm2) can also upset any assumptions of R1 (or Rn) to R2 ratios - so again don't get too precious about that kind of thing. Fundamantally as long as Zs is within limits, then ADS should work OK and the circuit should be safe from a shock point of view (at least for earth faults).


Insulation tests can be done once per CU rather than on each individual final circuit (despite the model forms, BS 7671 doesn't actually require per-circuit insulation tests). L+N to PE will reveal the vast majoriy of faults, especially when wired in T&E, so that'll usually suffice. Yes, some electronic equipment has components L/N to PE (usually capacitors for EMI filtering purposes) which can mess up insulation test results (including some RCBOs with a white wire of course). Try the test at 250V first (as that shouldn't damage anything) and only if it's low start hunting for any hidden items. Once it's clear, try the test proper at 500V. In terms of form filling, if you know that the entire installation has an insulation resistance of a certain value, then you can be sure that each circuit will have a insulation resistance of at least that - mathematically it's impossible for it to be lower - so you can correctly write "≥ (your whole CU value)" for each circuit.


Don't skip on the Mk1 eyeball (or nose) tests - they'll probably lead you to problems quicker than meter based tests.


Try to cover yourself in the 'limitations' section of the report - explicity agreed with the person ordering the work of course - and make it part of your template form so you don't have to add it to each report manually.


   - Andy.

Thanks Andy. Ive been moving more towards the R2 method but habit keeps taking me back to what ive previously done so much. I think the R2 wander lead is going to be the staple.


Very happy to learn connecting the R2 lead to a screw terminal of wiring accessory - Im actually excited to witness the potential time saving there!


In the time I have im inclined to do the end to end tests on the ring and provided all are ok, do a ZS and thats it. If any of the results are not good then an individual I.R test and possibly split the ring in to two radials.


70% of the "ring" circuits I have tested so far have been C2. New build is the worst.


Going to try making a scratch on the cooker casing to get an r2 all the way through as I agree regarding dismantling - Old equipment often doesn't tolerate beinng dismantled but was wrking perfectly before trying to gain access. New equipment installed by apprentices - Grub screws rounded or broken, socket back boxes cross threaded or destroyed etc etc Failing that a test on the screw terminal at the flex outlet


Thanks for your reply some tips in there to take forward


 

mapj1:

Ignoring the fact that others have pointed out,  that in that time at best it will probably be mostly a 'visual only ' inspection, and anything with complexity more than a garden shed with one light and a double socket circuit is going to take longer...

(There is a tendency to do very weak testing, and repeat it too  often, instead of a full drains-up but less frequently which would represent better value. Price and a desire for some paper with a recent date is the driver)


Couldnt agree more with that statement.  Proper EICR's will keep electrical systems running propaerly for a very long time not to mention safety. The difficulty I fid with getting the message across is that often, a customer has been living in a death trap for many many years. I tell them the danger and they shrug their shoulders and say ive been here for 25 years and its been fie.


Well yes, but tomorrow you may burn to death in your bed whilst rading the latest Harry Potter Novel.


 

The tech bit

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.


I cant remember whether I encountered this when I was doing EICR's regularly - Would this be what you would find on immersion circuits? And if so why is that? Ive been regularly finding 4/6mm earth coming out of fused spurs near areas with lots of pipe work in there properties. I assumed this was some effort of supplementary bonding and having visually inspected and tested bonding etc - Left it as it was. I wasnt installing under 16th Edition regs!


 

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.

Thanks - Neons are between Line and Neutral? The test was an individual circuit on the ring. Results were 1.51 for neutral end to end, 1862 Line end to end and >2000 for R2 end to end. I.R was 0.79 mega ohms (LINE+NEUTRAL to earth) rig circuit covers entire house including kitchen. The circuit was originally on an RCBO but I removed the line and neutral from the RCBO _ Im wondering if thats the cause there.

Neons are between Line and Neutral?