r1+r2. calculate or measure...

[sparkzalot]

Please discuss...

 

[Leesparkykent]

Please discuss...

Discuss what?

 

[davesparks]

Calculate when designing circuits, measure when carrying out testing

What is there to discuss?

 

[Dave OCD]

Obviously it has to be measured when testing, otherwise how can you be certain your circuit will disconnect as it should under fault conditions ?

 

[DuaneMHunt1976]

(r1 + r2)/4=R1+R2
So you know what you get when you cross them over at each socket.
I hear some miss doing the cross overs and just check the with a socket tester.

Have I gone off on a tangent again!

 

[davesparks]

Not off tangent at all, you actually make a good point. I for one had just assumed the OP was meaning R1+R2

 

[HappyHippyDad]

Please discuss...

Sorry, you just haven't introduced me to the topic of discussion in an attractive enough manner so I shall continue with my cup of tea and my book!

 

[sparkzalot]

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

 

[davesparks]

There is nothing to discuss.
You carry out either R1+R2 or R2 test.

 

[DuaneMHunt1976]

You measure R1+R2 as this also show continuity R1+R2=Zs-Ze
Measure.Zs were possible Zs=Ze+R1+R2
Ze by asking or measuring Ze=Zs-R1-R2

Also note that r1, r2, and rn are ring values

 

[sparkzalot]

There is nothing to discuss.
You carry out either R1+R2 or R2 test.

Some do Zs. Not R1+R2. So a discussion of what people do...

 

[DuaneMHunt1976]

:81: I'm lost now, he said do R1+R2 or R2 and you read that as don't

 

[shanky887614]

to be honest a measured value is always better than a calced value but if you cant turn it off then a Zs and Ze test with calced R1+R2 is normally accepted as a compromise.

 

[sparkzalot]

So they do. My point is simple enough isnt it??

 

[davesparks]

So they do. My point is simple enough isnt it??

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.

 

[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.