High Zs values (Just)

[telectrix]

to throw the cat into the pigeon coop........ so we are believing that a , say, 0.4 sec. disconnection time cannot be achieved if the Zs of a circuit is a fraction of an ohm above the BS7671 ( corrected, Cmin etc.). who's to say if this is dangerous, or potentially dangerous? how can anyone assume that a person in contact with a "live" exposed part and an extraneous part cannot endure a touch voltage of <50V for a split second longer without dying? have the IET done some tasting on animals to prove or disprove? or is it a case of "let's make something up to justify new regs./amendments?

 

[Toneyz]

Why was this Cmin not come to light years ago it must have always been something to take into account.
You know what will happen next, although in the table it gives maximum Zs values they will write a new reg that states any new circuit must be designed to a max percentage of that to give allowances.

 

[Ian1981]

to throw the cat into the pigeon coop........ so we are believing that a , say, 0.4 sec. disconnection time cannot be achieved if the Zs of a circuit is a fraction of an ohm above the BS7671 ( corrected, Cmin etc.). who's to say if this is dangerous, or potentially dangerous? how can anyone assume that a person in contact with a "live" exposed part and an extraneous part cannot endure a touch voltage of <50V for a split second longer without dying? have the IET done some tasting on animals to prove or disprove? or is it a case of "let's make something up to justify new regs./amendments?

Not sure you can write that on your report tho
If you can’t guarantee the disconnection times quoted by the regulations by using the generic time curves or the manufacturers data for their OCPD’s then you can’t fully comply with the regulations regarding fault protection.

 

[Deleted member 9648]

I'm not going to argue with anyone who advocates a code 2. That's an interpretation which can be justified. But my interpretation is that a compliant circuit is not safe one day and potentially dangerous the next simply because some boff playing with figures moves the goalposts to justify his existence.
However as already stated I will discuss the issue with my NICEIC inspector on his next visit and if he thinks a code 2 is appropriate then that's what I'll do in future...…(through gritted teeth mind you)

 

[Ian1981]

I'm not going to argue with anyone who advocates a code 2. That's an interpretation which can be justified. But my interpretation is that a compliant circuit is not safe one day and potentially dangerous the next simply because some boff playing with figures moves the goalposts to justify his existence.
However as already stated I will discuss the issue with my NICEIC inspector on his next visit and if he thinks a code 2 is appropriate then that's what I'll do in future...…(through gritted teeth mind you)

Keep us updated if you don’t mind if your inspection is anytime soon?
Would be interested to hear another opinion on it

 

[westward10]

Mmm, wonder what this opinion will be

 

[Wilko]

For me it's C2 on a report (sorry). Getting very imaginative - the "fix" could be a temperature and load study proving headroom in the 80% factor, but only in a managed installation. This would then be written onto EIC as a deviation.

 

[Deleted member 9648]

Visits not far away, will update when I get his opinion. I'll wager it'll be a 2.

 

[Ian1981]

Visits not far away, will update when I get his opinion. I'll wager it'll be a 2.

For what it’s worth, I get your point and I don’t want to come over as argumentative.
Just my opinion is all.

 

[Intoelectrics]

to throw the cat into the pigeon coop........ so we are believing that a , say, 0.4 sec. disconnection time cannot be achieved if the Zs of a circuit is a fraction of an ohm above the BS7671 ( corrected, Cmin etc.). who's to say if this is dangerous, or potentially dangerous? how can anyone assume that a person in contact with a "live" exposed part and an extraneous part cannot endure a touch voltage of <50V for a split second longer without dying? have the IET done some tasting on animals to prove or disprove? or is it a case of "let's make something up to justify new regs./amendments?

I did some tasting on a couple of animals last night. I had a chicken and lamb curry, it was delicious.