Zs and more Zs

[scotsparky]

these figues that the Supply authority will say depending on the supply.

Be carefull with TT systems as the supply authority will state 21 Ohms this is the resistance of there earth rod at the transformer. When you install an earth rod the combined resistancce of your rod + theres must be under 200 ohms.

 

[scotsparky]

From what I understand, their argument is that EAWR doesn't allow live working.
As such the Ze and Zs tests are not allowed, as Ze can be obtained through enquiry and Zs by calculation.

The EAWR does not allow live working yes i agree However it does allow for live testing as the live parts are exposed but there is no interference with the system exept the insertion of GS38 probes connected to a meter all of which comply to current safety standards.

 

[scotsparky]

Be carefull if relying on inquiery as i have found wrong presentation of cable heads with no earth at all.

If you are unwilling to pull fuses then note on a PIR as a limitation and take a ZS at the nearest point of origion where access can be obtained. (normally the main isolator.)

 

[IQ Electrical]

Yes, Rb = max 21 Ohms

Ra+Rb should be under 200 Ohms.

Or under 100 Ohms if you read BS 7430

Someone just removed the post I'm replying to, it looks like I've lost the plot!

 

[Deleted member 26818]

The EAWR does not allow live working yes i agree However it does allow for live testing as the live parts are exposed but there is no interference with the system exept the insertion of GS38 probes connected to a meter all of which comply to current safety standards.

As IQ has already posted, the EAWR do not distinguish between working and testing.

 

[johnnymacc]

Elecsa EIC asks for maximum measured Zs

 

[IQ Electrical]

Elecsa EIC asks for maximum measured Zs

They all do, they're based on the IET model forms, the thread is really about Ze.

 

[ian.settle1]

with your tongue?

 

[johnnymacc]

Sorry thought we'd strayed onto wether to test live or calculate Zs,model forms in Appendix 6 just asks for Zs doesn't state has to be measured or calculated.

 

[scotsparky]

EFLI testing is live testing. This Live testing involves working on or hear live conductors. It is unlawful to work on or near live conductors under Regulation 14 of the EAWR 1989 unless " it is unreasonable in all the circumstances for it to be dead".



Pinched the above section from an IET forum on this sam subject.

THe key words are "is it un reasonable in all circumstances for it to be dead" how do you do a dead ELI or RCD test? It has to be live so then work out a risk assesment. GS38 probes ect which means you then comply with EAWR

 

[Deleted member 26818]

BS7671 allows for Ze and PFC to be obtained by enquiry, as such it is not whether it is reasonable for it to be dead, but whether it is neccessary at all.
RCDs and Zs at socket-outlets can be tested with out the need to expose live conductors, as would functional testing of switches and RCDs.
Zs for other circuits can be obtained by calculation.
As such, it would appear that the only test required to be conducted live with exposed conductors, is polarity of supply.

 

[scotsparky]

In my opinion itn is always better to measure the Ze it is allowed and gives a good indication of the quality of earthing. I have found that the supply authority do not always know the supply arrangement or give the stock answer of " we dont have to supply an earth"

 

[telectrix]

i learnt to test Zs and all other live tests by testing on live circuits. i also learnt to ride a bike with wheels on it. i shall continue to ride a bike with it's wheels attached, same as i will continue to test as i've always done. seems the next generation of sparkys won't be able to install anything in case the screwdriver slips cuts their lily whites.

 

[andyb]

. i also learnt to ride a bike with wheels on it. i shall continue to ride a bike with it's wheels attached, same as i will continue to test as i've always done. seems the next generation of sparkys won't be able to install anything in case the screwdriver slips cuts their lily whites.

Telectrix, how on earth do you ride a bike without the wheels?

 

[gamblor6]

live testing is allowed as long as barriers are in place ie. thick clear plastic sheet

 

[IQ Electrical]

live testing is allowed as long as barriers are in place ie. thick clear plastic sheet

I think you're missing the gist of the thread.