A testing question for assessment.

[Goody]

I have checked couple of books and searched thro' the Internet; I do not find an emphasis on finding R1+Rn on lighting circuits. On an old thread here -> http://www.electriciansforums.net/i...ctrical-installations/7114-rn-continuity.html I have found the following:

Question:

IV JUST DONE MY PART P, HOWEVER IV BEEN GOIN OVER ALL MY NOTES ETC AND HAVE REALIZED THAT WHEN WE DO DEAD TESTS ON SAY A LIGHTING CIRCUIT WE TEST
R1+R2 FOR CONTINUITY AND POLARITY .
BUT WHY DONT WE TEST CONTINUITY OF RN? SURELY WE WANT TO MAKE SURE RN IS CONECTED SECURELY AND NOT DAMAGED, AND I KNOW WE DONT NEED TO RECORD THIS EITHER BUT SHOULD WE NOT TEST IT SAY WITH R1 +RN CONECTED? ???
GOT A SIMILUR QUESTION ASKED IN ..dead test>
THAT GOT ME THINKIN BOUT THIS

RN CONTINUITY..


ANYONE? AS IM PUZZELED AND PROB JUST OVERLOOKIN THE OBVIOUS AS USUAL

Answer:

It's done on ring circuits but not as you say on radials.

 

[Sparky Ninja]

If anybody is still confused about weather, or weather not to carry out an R1&RN test then it is better to carry it out, to allow themselves to consider its purpose.

The most common requirement is the second step for continuity of a ring final circuit. I myself will also do an R1&RN on any radial circuit that incorporates sockets outlets, as carrying out an R1&RN is best for both polarity and functional tests in these cases (not forgetting double pole switch sockets, the neutral will require functional testing).

With regard to other circuits, I would refer to GN3 section 2.7.19 Verification of voltage drop.

This test isn't required on a new installation or initial verification as volt drop will be considered with a new installation in the design phase.

But consider, however, going to do a periodic where there is a shower circuit that was installed 10 years ago. Back then the proper calculation would be done for the then selected shower load (say a 4.5kW) and then some time later the shower failed or the home-owner wanted an upgrade. They get a plumber to do all the work and connect in the new shower, which is now a 6.9kW. The plumber (or other non competent person) has failed to take an assessment on the circuits new design current, considering the change in volt drop resulting from it.

It's the job of the sparky to make an assessment for voltage drop to assess if the loads or use of the installation have changed over time and are no longer accommodating their design.

For us to do this we have to take a measurement of the CIRCUITS impedance. This means R1&RN and not R1&R2. We use the formula Vd = (R1&RN) x Ib x F where F is commonly 1.2

 

[Deleted member 26818]

The thing about testing Rn continuity, is that if there is none, the circuit will not work.
This usually can easilly be ascertained by simply plugging something in, or in the case of a lighting circuit inserting a lamp in the lamp holder.
R1 + R2 will indicate whether the Circuit Protective device will work within the specified time.

 

[Des 56]

For us to do this we have to take a measurement of the CIRCUITS impedance. This means R1&RN and not R1&R2


Or use direct measurement with a voltmeter

 

[Sparky Ninja]

For us to do this we have to take a measurement of the CIRCUITS impedance. This means R1&RN and not R1&R2


Or use direct measurement with a voltmeter

Two persons taking a value at the same time at both ends, sure.

 

[Goody]

I do not dispute any of these; it's good to read R1+Rn on radials to ascertain any hidden flaws. But finding R1+Rn on lighting circuits is not stipulated in testing books / procedures. I am intrigued if the assessor will insist on seeing such test had been carried out.