Consumer unit change testing

[Ghost2011]

hi all I've got my first consumer unit change to do as I'm using this as my first nic assessment. My question is when doing my ir test the whole house is on led downlights about 30 of then plus under kitchen 12v led and a lot of sub sockets, will all,of theses need to be disconnected to do these test. Also do I need to do r1+r2 on every downlight.

Any advice is much appreciated as this is my first nic assessment after this change.

Thanks

 

[andyb]

Just IR test between LN together and earth.
R1+R2 from furthest point.

 

[westward10]

Agreed.

 

[Ghost2011]

So by doing the ln together and earth for each circuit this would mean that I don't need to disconnect all LEDs or sensitive equipment.

 

[Octopus]

Don't take this the wrong way but do you think you think you are ready for the assessment?

 

[Ghost2011]

I can see why you would ask that I just don't want to mess anything up as I haven't done the ir test this way before it just so happens this house has a lot of LEDs and sub sockets in and would take ages to go round and take everything out then put back in. So I would rather check first as this way will save a lot of time.

 

[Taylortwocities]

As above. Tie L & N together and IR test between that and earth.
If you are really unsure, wind your IR tester down to 250VDC for the test. No need to go for 500V if the test results at 250 are OK.

 

[charlie76]

Just IR test between LN together and earth.
R1+R2 from furthest point.

I would measure R1 + R2 at each light fitting. How is he proving continuity of protective conductors by only testing at the final light fitting?

 

[Octopus]

The ideal way to do proper tests is well and truly screwed by all these fittings.

 

[westward10]

As above. Tie L & N together and IR test between that and earth.
If you are really unsure, wind your IR tester down to 250VDC for the test. No need to go for 500V if the test results at 250 are OK.

500v is the required voltage.

 

[mark.]

I may be wrong, (I am new to this). but i thought you could use 250v as long as the results comply with 500v

 

[The Ghost]

Regs say 500v but sometimes I test at 250v where there is equipment sensitive to damage. But really speaking it will be a departure from regs to leave it at that.

 

[LankyWill]

I would measure R1 + R2 at each light fitting. How is he proving continuity of protective conductors by only testing at the final light fitting?

If there was a break in the earth conductor prior to the final light, he wouldn't be able to get the reading as there would be no earth path back to CU.

I rarely bother with R1+R2, usually Zs-Ze although i feel thats a brave statement on this forum

 

[HandySparks]

I would measure R1 + R2 at each light fitting. How is he proving continuity of protective conductors by only testing at the final light fitting?

House with, say, 100+ recessed downlights and you're going to pull each one out of the ceiling. Pull the other one.

 

[bigspark17]

Your testing to ensure the circuits are safe to renergise and surely put cu change only on eic extent. I would suggest end of line zs, L&N - earth IR, continuity of ring end-end conductors
On final circuits would achieve this.

 

[Toneyz]

If there was a break in the earth conductor prior to the final light, he wouldn't be able to get the reading as there would be no earth path back to CU.

I rarely bother with R1+R2, usually Zs-Ze although i feel thats a brave statement on this forum

Zs - Ze Please tell me your joking

 

[hightower]

Zs - Ze Please tell me your joking

I've heard a number of sparks say Zs - Ze = R1 + R2 (including my uncle who I work for)..... wowser.

 

[westward10]

Zs-Ze=R1+R2, indeed it does.

 

[Midwest]

ohhh, here we go. Nothing good on the tele

 

[LankyWill]

Zs - Ze Please tell me your joking

Joking im not. Zs-Ze does equal R1+R2, its a very popular method of testing and not to mention quicker.

 

[GL4Spark]

I understand some people have stated you cannot use Zs - Ze to calculate R1 + R2 due to parallel paths being present... but aren't they also present during continuity tests? I have always been told you can't backwards calculate but now I'm curious as to why

 

[Toneyz]

It is the resistance of the line and cpc conductors of that circuit,I'm not saying that in most cases the result is about the same.eg you do a loop test of a circuit take a immersion heater circuit and that circuit cpc is loose/broken etc loop test shows earthing ok due to a paralell path of the copper pipe via water bond pipework gets altered plastic intersection T added to pipe for other water supply that paralell path is no more then there is no earth to that circuit.

 

[unconditional]

Low current testing is also more revealing of faults like high resistance connections than plugging in a loop tester. Is voltage sensitive equipment still an issue with modern testers at 500v? I know the current limiting on mine stops at quite low voltages on lower resistances, and only applies 500 on big resistances.

 

[GL4Spark]

But if you were to do an (R1 + R2) test on said immersion circuit with the broken cpc you would also get a reading would you not? I understand what you're saying but the regs don't require us to remove bonding conductors for the test, so we would have parallel paths in both cases.

 

[Risteard]

There is no merit in this Zs-Ze approach. The whole point of a dead continuity test is to ensure the cpc is there BEFORE energising. If a live Zs test is just done then there is absolutely no point in pretending R1+R2 was measured just to fill in a box.

So do an R2 or R1+R2 before energising, or if you just do the Zs then at least state that that is all you have done rather than making up useless figures.

 

[westward10]

This is not an Initial Verification and tests can be carried out as if it was a Periodic Inspection in which case it is perfectly acceptable to use the EFLI test as proof for earth continuity.

 

[Risteard]

This is not an Initial Verification and tests can be carried out as if it was a Periodic Inspection in which case it is perfectly acceptable to use the EFLI test as proof for earth continuity.

Well, it is an initial verification (hence the Electrical Installation Certificate). BUT the certified work relates ONLY to the replacement of the distribution board (which will be clear in the extent of the installation work undertaken box), and essentially the tests carried out following the inspection are simply to ascertain that the existing circuits are safe to put back into service on the new distribution board. You are not taking ownership of the existing installation. After all you cannot verify the route the wiring takes or any number of other things about the prior installation methods.

It still doesn't explain why you feel the need to fill in a box for something which you are stating that you have not tested and have also stated that you do not need to test. If that is your position then do not fill the box for it in! To do so is both misleading and pointless.

 

[westward10]

Has been tested by way of EFLI.

 

[Risteard]

Has been tested by way of EFLI.

Earth continuity has been verified with a Zs test. So why are you filling in a box stating R1+R2? You haven't done this test (which is not a criticism) - but why are you filling the box out? That is misleading and serves no purpose.

 

[westward10]

Earth continuity has been verified with a Zs test. So why are you filling in a box stating R1+R2? You haven't done this test (which is not a criticism) - but why are you filling the box out? That is misleading and serves no purpose.

I don't recall stating which boxes I fill in, I just agreed that Zs-Ze=R1+R2.

 

[Risteard]

I don't recall stating which boxes I fill in, I just agreed that Zs-Ze=R1+R2.

It doesn't really. It can verify cpc continuity in an already energised installation which is fair enough. But some people are advocating noting down a reverse engineered value under the dead continuity test boxes which is frankly a nonsense.

 

[HandySparks]

It still doesn't explain why you feel the need to fill in a box for something which you are stating that you have not tested and have also stated that you do not need to test. If that is your position then do not fill the box for it in! To do so is both misleading and pointless.

Totally agree. My certs usually have loads of unfilled boxes. If I didn't check or measure something, it doesn't go in the box. And if I measure something once it only gets written down once. So, for RCD times, the values go on a line for the RCD and not on the lines for every circuit it protects.

 

[Risteard]

So, for RCD times, the values go on a line for the RCD and not on the lines for every circuit it protects.

Personally for an RCCB I list the times next to each protected circuit rather than list the RCCB separately on a line of its own. But so long as what you have is clear then I don't have a problem with it being done that way.

 

[westward10]

It doesn't really. It can verify cpc continuity in an already energised installation which is fair enough. But some people are advocating noting down a reverse engineered value under the dead continuity test boxes which is frankly a nonsense.

It isn't necessarily nonsense, where there are no parallel paths the reading is probably quite accurate. This isn't much different to people calculating Zs which I have seen recommended on this forum where a live reading should be obtained. For example dead testing R1+R2 then adding on Ze.

 

[Risteard]

It isn't necessarily nonsense, where there are no parallel paths the reading is probably quite accurate. This isn't much different to people calculating Zs which I have seen recommended on this forum where a live reading should be obtained. For example dead testing R1+R2 then adding on Ze.

A calculated Zs will err on the side of safety. To reverse engineer the R1+R2 will err on the side of danger. It also serves no purpose when you are verifying cpc continuity on an already energised installation with live (Zs) testing. Filling in a box simply because it exists on the form has no merit when you are excluding dead continuity tests. If you are excluding it then exclude it!

 

[Andy78]

It isn't necessarily nonsense, where there are no parallel paths the reading is probably quite accurate. This isn't much different to people calculating Zs which I have seen recommended on this forum where a live reading should be obtained. For example dead testing R1+R2 then adding on Ze.

It is entirely different to calculating Zs.
Calculating Zs from (R1+R2)+Ze gives a value based on two measured readings, so it is not really calculated, merely an addition of measured values. It also gives a worst case scenario, a maximum figure for Zs for that circuit without any connected parallel paths to earth that, if compliant, can only mean that a live (connected) Zs will be less and therefore also comply with disconnection times. That is the reason this value is permitted to be entered as a value on a schedule of test results to BS7671

Calculating R1+R2 from Zs by subtracting Ze accounts for no connected paths and therefore will not be accurate. As Risteard says, this is an valid enough method of verifying continuity of protective conductors on an already energised circuit, but not a valid way of obtaining a reliable value of R1+R2.

 

[davesparks]

I may be wrong, (I am new to this). but i thought you could use 250v as long as the results comply with 500v

No, 250V is below the peak voltage it will normally be exposed to so is a useless test as far as proving the integrity of the insulation.

 

[davesparks]

Joking im not. Zs-Ze does equal R1+R2, its a very popular method of testing and not to mention quicker.

That is not a method of testing, it is a method of calculating an estimated value.

It is not a viable method of attaining a value for the continuity of the CPC, for initial verification it is a requirement that the R1+R2 or R2 be measured prior to making a circuit live,

 

[E.E.I]

What about when live testing through RCD's, this gives a higher value on your zs reading. This would effect the calculated R1+R2

 

[davesparks]

What about when live testing through RCD's, this gives a higher value on your zs reading. This would effect the calculated R1+R2

Just don't live test through the RCD, use a more suitable test method

 

[LankyWill]

That is not a method of testing, it is a method of calculating an estimated value.

It is not a viable method of attaining a value for the continuity of the CPC, for initial verification it is a requirement that the R1+R2 or R2 be measured prior to making a circuit live,

not sure thats fact dave, im sure it states, measure or calculate. If the earth path was compromised the zs reading would show this so its no different to R1+R2 and saves loads of time.

 

[Andy78]

not sure thats fact dave, im sure it states, measure or calculate. If the earth path was compromised the zs reading would show this so its no different to R1+R2 and saves loads of time.

If you are not sure that what someone says is a fact it is customary to quote a fact to back up your contradictory viewpoint.

 

[LankyWill]

If you are not sure that what someone says is a fact it is customary to quote a fact to back up your contradictory viewpoint.

get back in your cave troll

 

[Andy78]

get back in your cave troll

Oh I'm no troll. Just pointing out that your assertions of "its' quicker" and "I'm not sure that's fact" don't really hold any weight in a debate about technical issues.

 

[HandySparks]

get back in your cave troll

If Andy78 is a troll, you'll be able to give us the reg number that you're quoting from.

 

[Toneyz]

What about presence and adequacy of circuit protective conductors (411.3.1.1 543.1) if you are doing a EICR before replacing a consumer unit

 

[Toneyz]

I don't recall stating which boxes I fill in, I just agreed that Zs-Ze=R1+R2.

how can it if R2 is not continuous and your return earth is by other path that has a very low resistance when you do loop test

 

[charlie76]

I often take my feed for downlights in and out of a wago box and take a single T+E into the light fitting because its a lot easier at the fitting to get one cable in. See picture. Lets now say we only test R1+R2 at the last device or extremety of the circuit I will get the same reading regardless of whether or not I have the downlights fitted. Now add the downlights and make a poor earth connection in the wago box so the downlight is not earthed. R1+R2 is still the same and gives a good reading at the end of the circuit, but the downlight is not earthed. I have maintained earth continuity to the extreme end of the circuit through the wago box connections but failed earth between one of the wago's and a downlight. In a house with 30+ downlights I may have made more than one poor connection between the wago box and the downlight meaning I have 1+ downlights un-earthed.

Hence I always test R2 at every accessory, you may think this OTT but it is so quick its not worth not doing. Wander lead and test to a metal part on the light, I bet you could do 30 in less than 10 minutes.

 

[charlie76]

hi all I've got my first consumer unit change to do as I'm using this as my first nic assessment. My question is when doing my ir test the whole house is on led downlights about 30 of then plus under kitchen 12v led and a lot of sub sockets, will all,of theses need to be disconnected to do these test. Also do I need to do r1+r2 on every downlight.

Any advice is much appreciated as this is my first nic assessment after this change.

Thanks

I think everyone has missed the question though. I recently had my first inspection with NAPIT on a rewire and what they are actually looking for is understanding, not that you do it on the day. If you say to the inspector "Do you want me to remove all 30 bulbs to carry out the IR test or are you happy to see it with L-N shorted" I would be surprised if he would say take them all out. And contrary to what others have said earlier, you do need to test at 500v but if you short L-N and test to earth you can do this because you are not creating any potential between L-N. If you understand that you should test with them all out and individually test the line and neutral conductors he will be happy that you understand what you are doing.

With your R1+R2 don't do it. Do a wander lead test to measure R2 at each light fitting. You are only REQUIRED to do R1+R2 on ring final circuits as with the ring final you must test the continuity of every conductor, and this is due to the inherent danger of a ring circuit if a conductor fails such as a line or neutral. In a lighting circuit should your line or neutral conductor not be continuous, the lights won't come on, in a ring circuit should a L or N conductor not be continuous, everything will still work correctly however you could be overloading the one continuous leg of the ring if you fully loaded it.

A bit of advice for the inspection is that provided you understand what you are doing and why you are doing it you will be fine. If you are limited by the fact that everything is second fixed and you are passed initial verification stage then explain to him what you did at initial verification stage and why you think it is not practical to do that test now. Offer him the opportunity to do it if he wishes but they are not monsters he won't want to see you removing all 30 lights.

 

[Wilko]

Hence I always test R2 at every accessory, you may think this OTT but it is so quick its not worth not doing. Wander lead and test to a metal part on the light, I bet you could do 30 in less than 10 minutes.

I'm a fan of the wander lead myself
If I'm unfamiliar with an installation (meaning I'm concerned it could be nasty) I often take a little walk around with Wanda and confirm what is connected to what.