Calculating Ze

[SPECIAL LOCATION]

That wasnt my point! The EAWR 1989 says14. No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless-

(a) it is unreasonable in all the circumstances for it to be dead; and

(B) it is reasonable in all the circumstances for him to be at work on or near it while it is live; and

© suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury. .........

That completely bu99ers up testing RCD's then!!!!!!!!!!!!!!!! headbang

I guess I better find a way to test them dead as well???

:innocent :_|

 

[SPECIAL LOCATION]

I was asked the other day by another electrician where does it say Zdb in the regs, can anyone now the answer without going through the BRB?

Post #20 on this thread...

way back in March 2009....

http://www.talk.electricianforum.co.uk/showthread.php?t=3588&highlight=Zdb

Zbd is Not actually in the regs...

As mentioned by that guinea pig!!!! :Blushing :Blushing:Blushing:innocent

:coat :C

 

[sanny]

That completely bu99ers up testing RCD's then!!!!!!!!!!!!!!!! headbang I guess I better find a way to test them dead as well???

:innocent :_|

its unreasonable to do this test dead and no way of calculating it so i guess you'll be fine! oh and sarcasm is the lowest form of wit! lol

 

[sanny]

What are you going to do on a PIR - start taking the DB apart so that you can measure your R1 + R2.......No, you measure Zs.

With the supply safely isolated link the earth terminal to the busbar with 2 croc clips and a lead switch the breaker on for the circuit your testing r1+r2 no need to take the DB apart!

 

[Doc Hudson]

With the supply safely isolated link the earth terminal to the busbar with 2 croc clips and a lead switch the breaker on for the circuit your testing r1+r2 no need to take the DB apart!

In many situations it is not practical or permissible to switch off a whole installation. Working with a partially live distribution board is therefore a necessity, which is why competence and qualified for the types of work undertaken is needed.

Doc H.

 

[kme]

All im saying is if you know the the 3 variables which make up Zs why measure it

But you don`t!!!

As the tame hamster has noted: parallel paths stuff that calc. completely; which is why Ze doesn`t equal Zdb. :x

As regards EAWR`89 / 14:

Again, Nicky has hit that one for you.....if you, personally, aren`t capable / competent to do the tests, then you shouldn`t be doing `em. If you do, get a zap which chucks you off the ladder & breaks your leg; HSE would try to blame YOU for the accident, as you were carrying out a proceedure above your skill level. :innocent

What HAS been said is to avoid; where possible, live Zs testing with probes. :C

On a TPN install, where Zdb is a required parameter; and you cannot isolate the DB to do an r1+r2 on the sub; you`ll be in close proximity to all live conductors with your exposed tips ( and, as an aside, there is also the small matter of PSC - which, I recently had to carry out on rising busbars within a steel enclosure - now THAT`ll wake you up if you get it wrong) bad day explode

I know you are primarily meaning domestic, but the same rules apply:

If someone doesn`t feel they can personally comply with EAWR`89, they should retrain as a traffic warden! ray

Its another one of those bits of "guidance" brought in to protect those who, to my mind, are not fully competent / properly trained to do the works (i.e. SOME 5DWs and NVQers.) X(

((wait for it...........))) :run

As the Albert would say: "Its only my opinion". :innocent

KME

 

[kme]

With the supply safely isolated link the earth terminal to the busbar with 2 croc clips and a lead switch the breaker on for the circuit your testing r1+r2 no need to take the DB apart!

But you`ll find THAT isn`t a recommended proceedure, either -apparently you could "forget" to remove the link before re-energising.

Although - I regularly do this:Blushing

KME

 

[sanny]

In many situations it is not practical or permissible to switch off a whole installation. Working with a partially live distribution board is therefore a necessity, which is why competence and qualified for the types of work undertaken is needed.Doc H.

im talking under normal circumstances! If the power cant go off

(a) it is unreasonable in all the circumstances for it to be dead; and

(B) it is reasonable in all the circumstances for him to be at work on or near it while it is live; and

© suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury.

then measure it by all means

 

[Andy™]

in reality there is a massive difference between live working and live testing. unfortunatly, EAW doesnt make the distinction.

if your not competent at doing a live Zs, then you shouldnt be doing any electrical work.

 

[Sidewinder]

Andy,

That is a distinction I am working HARD to get through to my colleagues at IOSH!!!

 

[Nicky Tesla]

Try saying Its like doing a driving test on a simulator

 

[Emperor Zurg]

can anyone help I am so confused by this... Zurg

 

[Apache]

can anyone help I am so confused by this... Zurg

Confused by what exactly? Ze testing or live working?

This thread is good and should answer your questions.

Summary - you can Ze test live, there is no other way of verifying earth. Remove parallel paths first. Testing live different to working live.

 

[binky]

But you`ll find THAT isn`t a recommended proceedure, either -apparently you could "forget" to remove the link before re-energising.

Although - I regularly do this:Blushing

KME

It's safer to disconnect live on top of MCB and take it to the earth bar - otherwise you might need the seal fairy and a BS88 fuse  :innocent

 

[Sidewinder]

It's only an almost 10 year old thread since the last response until Zurg resurrected it!

 

[phil d]

It's only an almost 10 year old thread since the last response until Zurg resurrected it!

He should have left it until next Monday, wasn't there something in the bible to do with resurrection on Easter Monday, lol

Incidentally that reminds me of an idiot a while ago who thought it was a wonderful coincidence that the celebration of Christs crucifixion and resurrection happened on a Bank holiday weekend, because if it hadn't we wouldn't get 4 days off work! I kid you not, lol

 

[kerching]

Fluke user says "I see Christmas Day is on a Friday this year"

metrel user says "lets hope it's not the 13th"

:slap