Consumer unit change and testing.

[the_mouse]

Hi,

I was observing/moithering a qualified experienced spark do a consumer change and got some questions to ask on the way he tested things (didn

 

[ADS]

Hi,I was observing/moithering a qualified experienced spark do a consumer change and got some questions to ask on the way he tested things (didn

 

[Andy™]

4) Upstairs lighting all the ceiling roses were painted over and nigh on impossible to remove the covers, any tips for removing theese.

hammer

 

[m4tty]

I know I may be pushing my luck a bit but is there any chance someone could list down the minimum/quickest tests when doing a board change as when I'm doing them I'm doing full testing ie initial verification. Sorry to butt in on your thread btw. Cheers

 

[the_mouse]

Hi

Re: This wouldn't give you R1 + R2, so what's the point in measuring it.

No need for R1 + R2 anyway, but 'Continuity of CPC' needs to be confirmed at furtherest point on each circuit and other relevant points. (e.g. metal switch plates & other exposed conductive parts).

It is acceptable to use Zs test to confirm continuity.

Can i ask why this wouldnt be R1+R2? in the books i have read and college, to test at all points including light switches the highest value would be R1+R2 for that circuit and sould be the furthest point, wouldnt the switch be the furthest?

:C or am i getting summat wrong??(most likely)

 

[Doc Hudson]

HiRe: This wouldn't give you R1 + R2, so what's the point in measuring it.

No need for R1 + R2 anyway, but 'Continuity of CPC' needs to be confirmed at furtherest point on each circuit and other relevant points. (e.g. metal switch plates & other exposed conductive parts).

It is acceptable to use Zs test to confirm continuity.

Can i ask why this wouldnt be R1+R2? in the books i have read and college, to test at all points including light switches the highest value would be R1+R2 for that circuit and sould be the furthest point, wouldnt the switch be the furthest?

:C or am i getting summat wrong??(most likely)

It does actually depend upon how the lights are wired, looped at fitting or looped at switch. A switch could have a longer earth path (R2), but because the power has got to get back to the light fitting the light will have the longer R1. As a general rule the fitting is the preferred place. though I can understand if the fitting is inaccessible or would cause damage to the decoration it may not be practical. As such a limitation may need to be noted and get your reading as near as possible.

Doc H.

 

[Theorysparky]

it would be for the cpc but not the live

but by doing the test at the ceiling rose you check the polarity and leave the switch in the ''on'' position ready for the IR tests.

the other point is that at the ceiling rose you get to see the wiring and an indication of the end of the cct

 

[Theorysparky]

Thanks Doc

beat me to it

 

[Doc Hudson]

5) Insulation resistance on the ring was done by connecting the 2 lines and 2 neutral together and testing to earth is OK on a CU change?

That's OK, but why was he IR testing individual circuits.

Only requirement is 'full board' IR test with L & N connected together and tested to earth.I

 

[Theorysparky]

Only doing full board IR test is not strickly correct. As if low readings are found, individual circuits need to be tested anyway. In which case testing individually whist swapping circuits onto a new CU is not a problem. It could also be more helpful to assist checking for circuits sharing a common neutral, preventing "borrowed neutral" problems.Doc H.

which if not done before cu change will cause big problems

you will then need to explain to the customer why it doesnt work and that it will cost more to investigate

by this time its too late to put the old one back

 

[Doc Hudson]

4) Upstairs lighting all the ceiling roses were painted over and nigh on impossible to remove the covers, any tips for removing thees.

you have to be careful of not damaging the customers decoration and some older roses could be brittle and break if you try forcing them open. Who pays if you mess up the lounge ceiling. Some of those plug in light adapters can allow you to get some readings onto the case of a fitting if it is metal. Also with some Class 2 fittings you may struggle to get an earth anyway.

Doc H.

 

[ADS]

HiRe: This wouldn't give you R1 + R2, so what's the point in measuring it.

No need for R1 + R2 anyway, but 'Continuity of CPC' needs to be confirmed at furtherest point on each circuit and other relevant points. (e.g. metal switch plates & other exposed conductive parts).

It is acceptable to use Zs test to confirm continuity.

Can i ask why this wouldnt be R1+R2? in the books i have read and college, to test at all points including light switches the highest value would be R1+R2 for that circuit and sould be the furthest point, wouldnt the switch be the furthest?

:C or am i getting summat wrong??(most likely)

R1 + R2 is only a requirement during 'Initial Verification' - i.e. new installation, as this is the only time you can get a true reading of the resistance of R1....Line conductor and R2....CPC

Doing R1 + R2 on a board change or a 'Periodic' is pointless because of the possibility of parallel paths.

If you look at Supplementary Bonding of a bathroom - the R1 + R2 measurement of a circuit would be measured before this bonding was installed because all earths, exposed conductive parts and extraneous conductive parts are then bonded together - giving a multitude of parallel paths which, in turn, would give false R1 + R2 readings - so what's the point in taking them.

You have to remember what you are actually confirming whilst aquiring your R1 + R2 - it is the continuity of protective conductors - the R1 + R2 measurement is a bi-product (and not even mentioned in the Regs)

Measuring Zs on a 'Periodic' or 'Board Change' is just as effective, with wander lead tests to 'Exposed Conductive Parts'.

I know I may be pushing my luck a bit but is there any chance someone could list down the minimum/quickest tests when doing a board change as when I'm doing them I'm doing full testing ie initial verification. Sorry to butt in on your thread btw. Cheers

From the ESC Best Practise Guide:

10.2. In addition, as a minimum, the following tests

should be carried out to the existing circuits

connected to the replacement consumer unit.

 

[batty]

If they have fancy metal light fittings it would be a good idea to test them rather than at the switch because you don't know who fitted them it maybe an idiot that did not connect the earth and if somebody gets a belt because you did not test them you would be liable. I always test all sockets incase somebody has not coonnected them correctly that to me is also important.

 

[Andy™]

you cannot be held liable for someone else's bodge.

still a good idea to test it though. the amount of times the earth doesnt get connected, either because they havent got a clue, or there just isnt an earth at the light

 

[batty]

[quote name='Andy

 

[Andy™]

just because you get an earth loop at end of circuit doesnt mean every metallic light is actually connected to earth.

your certifying your work. your not certifying someone else's bodge as safe

 

[batty]

So that it why its a good idea to test all metal light fittings not test at the switches.

 

[ADS]

So that it why its a good idea to test all metal light fittings not test at the switches.

Do this with a wander lead, like I said.

You only have to touch your probe to the light fitting or switch plate and prove continuity.

On plastic switches, touching one of the screws should be confirmation enough.

Obviously, if you don't get a beep/reading, then further investigation.

 

[SPECIAL LOCATION]

R1 + R2 is only a requirement during 'Initial Verification' - i.e. new installation, as this is the only time you can get a true reading of the resistance of R1....Line conductor and R2....CPCDoing R1 + R2 on a board change or a 'Periodic' is pointless because of the possibility of parallel paths.

If you look at Supplementary Bonding of a bathroom - the R1 + R2 measurement of a circuit would be measured before this bonding was installed because all earths, exposed conductive parts and extraneous conductive parts are then bonded together - giving a multitude of parallel paths which, in turn, would give false R1 + R2 readings - so what's the point in taking them.

You have to remember what you are actually confirming whilst aquiring your R1 + R2 - it is the continuity of protective conductors - the R1 + R2 measurement is a bi-product (and not even mentioned in the Regs)

Measuring Zs on a 'Periodic' or 'Board Change' is just as effective, with wander lead tests to 'Exposed Conductive Parts'.

ehhh??? ?:|

Parallel Paths

If the circuit you are testing is completely disconnected at the fusbox end..

i.e.

you had a Live Neutral and Earth conductor all dead and resting in your hand..

There will be NO parallel paths because the CPC in question is open circuit ..

Parallel means two opposite ends of something have two or more possible paths to get between two points...

So connecting 'L' & 'E' to each other isolated from the board would actually give R1+R2 when measured at the extremity of the circuit..

even if another conductor goes off to a tap, cuz it has no connection back to our "OPEN CIRCUIT" wires at the other end!

A single wire open circuit joined to another wire is NOT a parallel path.

R1+R2 Not even mentioned in the regs?????

Page 341.. for a start maybe?

model forms Schedule of test results

column 6 R1+R2

column 7 R2

* Astrix comment.. "complete either 6 or 7"

Guidance Note 3.... (Which is part of the regs) as referenced by regulation 612.1 on pg 157 of BS7671.

Page 49 of GN3 gives clear example of using R1+R2 to establish

"Earth Loop Impedance" not purely as a means of checking continuity!

That is under the Inspection part of Insp & Test

Page 75 gives guidance about checking Earth Loop Impedance when undertaking "DETAILED PERIODIC INSPECTION"

where paragraph 'd' states

Where protective measures are used which require knowledge of earth loop impedance, the relevant impedance should be measured, OR determined by an equally effective method

Equally effective methods include (R1+R2)+Ze

So R1+R2 is clearly mentioned in the regs..

AND

it can also be used during a PIR or CU change at the discretion of the electrician as an effective means of confirming maximum earth loop impedances are met.

:|

.

 

[kme]

With reference to the "test all sockets / class 1 light fittings" or not debate.

It mat not have been your work; but unless you are incredibly clever, to do a board change you have de-energised those circuits. When you`ve changed the board, you`re going to re-energise them; and a class 1 fitting without a CPC connection could be in a fault condition, with phase voltage on it. If you haven`t tested it, you don`t know; so you have effectively energised a dangerous and non-compliant circuit.

I do as Batty there, mate - IMO there is no other safe & compliant option.