r1+r2. calculate or measure...

[sparkzalot]

Please discuss...

 

[HappyHippyDad]

Apologies abit (very) vague . Upon undertaking a conditon report and the circuits have been energised for many years. Do you measure r1+r2 or just do Zs/Ze and calculate r1+r2. For socket circuits odviously the correct test procedure needs to be done.

For example R1+R2 on a lighting circuit in small flat is say 2.50ohms you'd immediately know loose connection. Yet you could take a Zs on the same circuit and it could be more like 0.70ohms. (something to do with the current from the test kit i believe, but i dont know correct terminology) I think its more important to do r1+r2 because of this. Also parallel paths occasionally bringing Zs values down.

Please discuss

Now thats more like it

I see what you are getting at now. The original question looked like 'do you measure or calculate?'... well I suppose that was the original question, which has an obvious answer as DS explained.

I think you are now asking (and possibly meant this is the OP) would you just do a Zs rather than measure R1+R2 and add it to Ze?

If it was a condition report as you state then I would do both. I would measure R1+R2 and measure Zs because that is what the form requires. If it was a small job that I was undertaking and it was a MWC being issued then I would just measure the Zs.

As said before the only time I would 'calculate' (ie look up the figures for R1+R2) rather than 'measure' R1+R2 would be when deisigning a circuit.

 

[sparkzalot]

No your point isn't simple enough, I haven't got a clue what you are talking about here.

You say some people just do a Zs test, and as I pointed out some people do no tests at all. Neither of these makes them correct just because some people do it.

I prefer to measure R1+R2 Ze and mostly calculate Zs. For the reasons i have explained above. Im after others opinions. Now im simply after a discussion on what others prefer / do and why. It really is simple buddy. It really is.

 

[davesparks]

I prefer to measure R1+R2 Ze and mostly calculate Zs. For the reasons i have explained above. Im after others opinions. Now im simply after a discussion on what others prefer / do and why. It really is simple buddy. It really is.

Yes it is really simple, you test the continuity of the CPC and you test the EFLI.

You test the continuity of the CPC either using the R1+R2 or R2 tests. On a condition report you generally test R2 rather than R1+R2 for reasons of practicality.
You test EFLI on the live circuit to ensure fault protection will operate within the required time etc.

DON'T CALL ME BUDDY!

 

[Darkwood]

Sorry boys- Stop this abrasive attitude it can only send this thread downhill, if you cannot be civil with each other stop replying and move on.

If you want to carry on then the thread will be closed and as we do not condone this type of abrasive attitude and we will implement a ban - if you feel any member is out of order then use the report button please don't take it on yourself to exacerbate the situation.

 

[Andy78]

It is permissable to calculate Zs from measured values. It is always preferable to measure Zs though.
It is not permissable to calculate R1+R2 from other measured values. It must be measured.

The main purpose of EICR testing is to ascertain compliance for disconnection times and safety for continued use of circuits.
To this end some £80 a time jockeys don't do continuity testing.
I always perform a full range of tests on all circuits.

I think this is what you were asking about.

 

[sparkzalot]

It is permissable to calculate Zs from measured values. It is always preferable to measure Zs though.
It is not permissable to calculate R1+R2 from other measured values. It must be measured.

The main purpose of EICR testing is to ascertain compliance for disconnection times and safety for continued use of circuits.
To this end some £80 a time jockeys don't do continuity testing.
I always perform a full range of tests on all circuits.

I think this is what you were asking about.

I agree. Thanks

 

[Deleted member 26818]

The form being completed is a 'Schedule of test results'.
As such there should be no calculated values.

 

[DuaneMHunt1976]

I really don't like the formula Zs=Ze+R1+R2
To me from a Maths/computers background were we use pure names 9=9
Were Zs is about (one low line with a wave live about) Ze+R1+R2
The formula is there to check, rough check
Just like (r1+r2)/4=R1+R2
And I know people cut out doing the cross overs and just charge the circuit up and use a socket tester
And guess.use.the formula instead of checking

 

[DaveyD]

Agree with Andy. I see no provision to calculate R1+R2 from ZS-ZE it has to be measured.
You can calculate or measure ZS.
If you are confirming polarity another way then you can also test and record the circuit cpc on radials with an R2 test

 

[malcolmsanford]

I'm assuming all our "testers" on here are working religiously to the GN3 and of course the BS 7671....... so in the GN 3 3.10.2 it clearly states that the inspector will deem appropriate what tests will be done, but being the helpful organisation the IET is, they do in table 3.4 give you a list of tests which they deem suitable for an EICR, but again use terms like where practicable.

The very first test is in fact testing for Protective Conductor Continuity and to do this they have again advised us in the notes to this table, aren't they helpful

The earth fault loop impedance test may be used to confirm that continuity of protective conductors at socket outlets and at accessible exposed conductive parts of current using equipment and accessories

I would have worded that slightly differently, but hey I'm not paid mega-bucks to produce it. But the bottom line is you don't need to take a R1 R2 reading
I of the same opinion of the IET on this one, because no matter how hard you try unless you have a Line and a CPC, you are never going to measure a Zs. So by getting your Zs you are confirming continuity of the protective conductor

So the bottom line is on an EICR you don't need to measure R1 and R2 nor do you need to do an R2. Again if there are past results and you find there is a discrepancy that you think maybe due to the installation breaking down/fautly etc, then of course you start testing more vigorously.

If your testing a light circuit that is 15mt approx long and in 1.5 singles and you get a Zs of 6 ohms then you know there is something wrong and more testing is needed.

It is after all common sense and not just reading a book like some seem to do

 

[GEOFF S]

The general test are as follows, ive omitted certain ones.

Before energization.

Continuity test of Protective conductors
Contivuity of Ring Final Circuits
Insulation Resistance
Polarity.

Energised tests.

Earth Fault loop impedanceA
Additional Protection
Prospective Fault Current
Functional Test

Cheers

 

[markc123]

Malcolm - i couldn't agree more.

A few years ago, i put a 'tick in the R1+R2 box - i got called up on it by a spark about 4months later. Only to shoot him down by showing him GN3.

Lots of sparks don't even understand what it means if you tick the R1+R2 box.

 

[GEOFF S]

Malcolm - i couldn't agree more.

A few years ago, i put a 'tick in the R1+R2 box - i got called up on it by a spark about 4months later. Only to shoot him down by showing him GN3.

Lots of sparks don't even understand what it means if you tick the R1+R2 box.

The Regs require a continuity test with a current not less than 200mA, this will not stress the installation nor verify terminations. iT does however show open circuit connections.

GN3 suggest where paralell paths exist when testing, the unrliable readings may be omitted and a tick put in its place.

whether you use R1 + R2, or the long wander lead, Personally, recording the values has a value. Most schemes probably insist on them?

Cheers

 

[markc123]

The Regs require a continuity test with a current not less than 200mA, this will not stress the installation nor verify terminations. iT does however show open circuit connections.

GN3 suggest where paralell paths exist when testing, the unrliable readings may be omitted and a tick put in its place.

whether you use R1 + R2, or the long wander lead, Personally, recording the values has a value. Most schemes probably insist on them?

Cheers

First and foremost you're supposed to identify parallel paths and where possible remove them for testing purposes only - so you get a proper reading.

I don't agree that recording an incorrect and unreliable value as opposed to a tick in that situation would be the correct way to fill your cert in. But thats just my opinion. Each to their own.

My view on the 'tick' is that you're ticking to confirm that you've done the R1+R2 and that the reading isn't reliable.

Mark.

 

[davesparks]

First and foremost you're supposed to identify parallel paths and where possible remove them for testing purposes only - so you get a proper reading.

I don't agree that recording an incorrect and unreliable value as opposed to a tick in that situation would be the correct way to fill your cert in. But thats just my opinion. Each to their own.

My view on the 'tick' is that you're ticking to confirm that you've done the R1+R2 and that the reading isn't reliable.

Mark.

If the reading is unreliable then it is a fail.