max zs table in the osg

[Jonspark]

the figures are given in BS7671 without the 80% correction factor. these are what i use. in winter when we are measuring @3 deg.C, not 20, should we then apply another correction?

dont know. just thought you had to apply appendix 14

 

[davesparks]

i know your not in Britain, but if you were, surely you'd have to work to BS7671 requirements?

wouldn't not meeting these requirements constitute a C2

A C2 would be the code applied to a potentially dangerous fault found on an EICR, there is no such thing on an EIC.
If he has used values other than those in the books and recorded this deviation as part of the installations documentation then as long as the testing proves that the circuit is within those values there is no problem. Bs7671 is not the be all and end all of electrical installation!

 

[Engineer54]

Perhaps i should of also pointed out that the typical Zs values measured on our projects will meet and exceed anything that's presently deemed as max Zs values...

 

[Jonspark]

A C2 would be the code applied to a potentially dangerous fault found on an EICR, there is no such thing on an EIC.
If he has used values other than those in the books and recorded this deviation as part of the installations documentation then as long as the testing proves that the circuit is within those values there is no problem. Bs7671 is not the be all and end all of electrical installation!

doesn't an earth loop impedance value greater than that required warrant a potentially dangerous fault, ergo C2?

which other values apart from the manufactures are there?

 

[Jonspark]

Perhaps i should of also pointed out that the typical Zs values measured on our projects will meet and exceed anything that's presently deemed as max Zs values...

and so they should!

 

[Engineer54]

doesn't an earth loop impedance value greater than that required warrant a potentially dangerous fault, ergo C2?

Been absolutely fine for god knows how many years, so what's suddenly changed to make previously stated accepted values now ''Potentially Dangerous''?? Answer '' ...NOTHING!!

 

[Sintra]

dont know. just thought you had to apply appendix 14

The column on the cirtificate where the value of max Zs is filled in is headed "max Zs permitted by BS7671"

 

[Jonspark]

Been absolutely fine for god knows how many years, so what's suddenly changed to make previously stated accepted values now ''Potentially Dangerous''?? Answer '' ...NOTHING!!

don't quite follow u eng, nothings changed! just saying that exceeding max zs values as given in BS7671 is a C2 is it not? or is it all FINE!!!!!!

 

[Jonspark]

The column on the cirtificate where the value of max Zs is filled in is headed "max Zs permitted by BS7671"

so you dont have to stick to the 80% rule?

I am genually interested in finding the correct answer for this, so any help is greatfully received.

 

[telectrix]

and just to muddy the waters further, manufacturers data could well give a higher figure. as long as the MCB/fuse will operate within the specified time, then bob's your dad's brother.

 

[Jonspark]

and just to muddy the waters further, manufacturers data could well give a higher figure. as long as the MCB/fuse will operate within the specified time, then bob's your dad's brother.

Thanks for that.

See Eng, you don't have to add shouty exclamation marks.

 

[Jonspark]

so, you work out your fault current which is dependant upon impedance (Zs) then look up the time characteristics data for disconnection time.

 

[Pete999]

A C2 would be the code applied to a potentially dangerous fault found on an EICR, there is no such thing on an EIC.
If he has used values other than those in the books and recorded this deviation as part of the installations documentation then as long as the testing proves that the circuit is within those values there is no problem. Bs7671 is not the be all and end all of electrical installation!

Electrical Installation Certificate EIC

 

[telectrix]

the time/current graphs in BS7671 are generic. different makes of OCPDs may well give different (better) figures.

 

[Engineer54]

don't quite follow u eng, nothings changed! just saying that exceeding max zs values as given in BS7671 is a C2 is it not? or is it all FINE!!!!!!

Think about it for a second, previously stated max Zs values satisfied ADS requirements, so how can you, (or should i say they) now say that they Don't??

Of all the things that needed sorting out within BS7671, max Zs values wasn't and still isn't one of them. A totally wasted Amendment opportunity all round, when you also take into account the plastic/metal CU farce!!!