Do you have to do loop tests on all circuits

[Buildall]

On the 17th edition forms it says maximum measured Zs yet I have read that it is better to find this buy calculation. Also testing smoke alarm, cooker and lighting circuits seems to me to be to dangerious for H&S.

 

[sparkytim]

Hi

Not sure exactly what you are asking.

Please can you explain what testing situation do you mean, verification of new work?, or for PIR (thats Periodic Inspection Report on an existing installation)

What do you mean by H&S?

 

[tom1]

think what he is asking is it ok to calculate zs on circuits were you cant plug in your tester, so its a bit dangerous to have live conductors exposed while you clip onto them.

if your live testing you need to be aware of people in the houes.

and i its ok to just calculate but i prefer live test, if i do calculate then i do ze live test

 

[m4tty]

Buildall dont take this the wrong way but have you ever had a domestic belt. It only tickles lol

Id rather do test live too as tom1 says just be careful

 

[sparkytim]

Ok Tom, if thats what Buildall means then yes it is ok to calculate Zs from adding your Ze or Zdb to your R1+R2, as you have measured both of these then it is a Measured result that you have and can go into the Measured Zs box on the cert.

The Niceic recommend this as the safest way to avoid Zs tests at other then socket outlets.

You still have to measure the Ze or Zdb live at the Consumer Unit but at least this is only one test live.

 

[sellers]

TBH the only people doing zs testing would be competent electricians who know how to handle a live open CU or switch and personally i always like to do zs tests rather than calculate it where practical.

 

[Buildall]

Ok Tom, if thats what Buildall means then yes it is ok to calculate Zs from adding your Ze or Zdb to your R1+R2, as you have measured both of these then it is a Measured result that you have and can go into the Measured Zs box on the cert.The Niceic recommend this as the safest way to avoid Zs tests at other then socket outlets.

You still have to measure the Ze or Zdb live at the Consumer Unit but at least this is only one test live.

Yes that was what I was asking. It was more about Health and safety as I thought the recomendations these days was just to test sockets and calc everything else. I am just playing catchup after being out of the business for the last 15 years.

 

[tom1]

Buildall dont take this the wrong way but have you ever had a domestic belt. It only tickles lol Id rather do test live too as tom1 says just be careful

would that depend on what your touching, with what body part, and what your stood on?

 

[wozz]

testing should be carried out as you go along not once you have finished the job. i like calcualting Zs most of the time as it is safe, and not all shocks tickle. obviously Zs sockets as this this also confirms polarity.

 

[ADS]

testing should be carried out as you go along not once you have finished the job. i like calcualting Zs most of the time as it is safe, and not all shocks tickle. obviously Zs sockets as this this also confirms polarity.

How

 

[Andy™]

obviously Zs sockets as this this also confirms polarity.

will only confirm live is in the right place. neutral & earth can be wrong

 

[ADS]

[quote name='Andy

 

[paul b b]

it depends on the job, if its downlighters i calculate, pendant i test. but i would not in front of an asesser, i would state that it is against H&S

 

[Voltimax]

With the majority of circuits being on RCD's/RCBO's, I actually prefer to calculate. When doing Zs tests the readings can come back alot higher than they actually are thanks to most trip locks and certain brands of RCD. Calculating also gives the resistance of the circuit without the parallel paths.

 

[ADS]

Calculating also gives the resistance of the circuit without the parallel paths.

But Zs is the 'impedance' of the loop path with parallel paths, so calculating doesn't work

 

[Andy™]

But Zs is the 'impedance' of the loop path with parallel paths, so calculating doesn't work

yes, but what if those parallel paths (gas/water) make it comply, but then get changed to plastic?

and you can always do Zdb + R1R2 to get a better result that Ze + R1R2

 

[ADS]

[quote name='Andy

 

[Andy™]

Measuring R1+R2 with nothing connected up, conductors not terminated in CU etc etc, and then adding this to Ze (sometimes from enquiry), is a poor substitute.

Ze + R1R2 is a worst scenario of Zs - in reality, Zs is going to be lower, which is usually a good thing.

i rarely calc Zs - easier to meaure most fo the time, and at least you know you havent left something disconnected (i.e your calc of Ze + R1R2 wont show that you have left earth disconnected at DB)

 

[sparkytim]

If the Zs complies by means of Ze + (R1+R2) which for RCD protected circuits is not normally a problem i.e. < 1666.66 ohms ok for 30 m A then the Zdb lower reading will also comply, hence this formula of adding your MEASURED readings is no problem.

 

[Lurch]

Measuring R1+R2 with nothing connected up, conductors not terminated in CU etc etc, and then adding this to Ze (sometimes from enquiry), is a poor substitute.

How so? Calculation will give you a higher reading than measured if anything so is arguably a better way of doing it as it's unlikely for other parallel paths to alter this reading by other people doing unrelated work etc... at a later date.

Not that I would usually calculate it, but I don;t have a problem with doing so at any time and wouldn;t be against anyone calculating Zs on all circuits.