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

 

[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.

 

[Pat H]

I was looking at my wander lead the other day and wondering why I hadn't thought of adapting a regular 50m mains extension lead to do the job? All I need is an adapter at each end to bring out the earth pin to 4mm and I'm good to go.
The resistance would be lower if I parallel all three cores up but that represents a slight issue if somebody plugged the other end in by mistake...
But for the money they ask for a wander lead ....

 

[GMES]

get back in your cave troll

No need for silly comments like that mate it just derails the thread. Lets keep it professional guys.
Onwards and upwards!!!

 

[charlie76]

I was looking at my wander lead the other day and wondering why I hadn't thought of adapting a regular 50m mains extension lead to do the job? All I need is an adapter at each end to bring out the earth pin to 4mm and I'm good to go.
The resistance would be lower if I parallel all three cores up but that represents a slight issue if somebody plugged the other end in by mistake...
But for the money they ask for a wander lead ....

The resistance does not matter - Either zero it on your meter or deduct it from your measured value. You are right though they do charge an awful lot for what they are...

 

[Midwest]

I think this thread got derailed after the first page, when it went off on a tangent.

OP have your questions been answered, or are you more confused than when you opened this thread

 

[Ghost2011]

I think this thread got derailed after the first page, when it went off on a tangent.

OP have your questions been answered, or are you more confused than when you opened this thread

There has been a lot of help with my questions I have now done the change and everything was fine now just got to wait for the assessment next week fingers crossed but with others I have spoken to and seen my work all say there is no reason it shouldn't go smoothly. I'm sure I'll have more questions to come but everyone on here's seems helpful and freindly so I won't be afraid to ask.