Big Clive's "Trashy" meter, unboxed ( Duratool D03047 multimeter )

[Someone]

Really.

As I said, I have worked in electrical trades in the past. Employers had need for various test equipment that I used in industrial commercial and residential settings. Currently do not have the equipment to measure fault currents (safely or accurately) or even a mains current clamp....

Is the maths or reference to standards I present somehow questionable because of the lack of current equipment that I personally own? Is the personal equipment I own related to my knowledge of safety regulations or a desire to not see people encouraged to ignore them? No. Take your FUD and shove it.

[joeqsmith]

Is the maths or reference to standards I present somehow questionable because of the lack of current equipment that I personally own? Is the personal equipment I own related to my knowledge of safety regulations or a desire to not see people encouraged to ignore them? No. Take your FUD and shove it.

It's fine when you question my statements and ask me to show data to back up my claims.  Guessing you were not expecting me to actually follow through.  Now that I have and the roles have changed you start whining and telling me to shove it.       

[rsjsouza]

The meme below comes to mind...

[Someone]

It's fine when you question my statements and ask me to show data to back up my claims.  Guessing you were not expecting me to actually follow through.  Now that I have and the roles have changed you start whining and telling me to shove it.       

Quite the opposite, I'm happy there are some measured numbers for people to consider but typical figures or calculated examples would have been fine. All I was after was the prospective fault current as your prevailing local standards (of which I know almost nothing about) were likely to be different to the standards we have here.

Measurement categories from 61010 are international and to protect people from (almost) worst case conditions (including faults and transients). Simple rules with almost universal application. Many things could make specific installations/setups less dangerous than that but its then down to (learned) people applying that specifically and not trying to extrapolate out to other situations.

[Someone]

The meme below comes to mind...

joeqsmith measuring a prospective fault current on a socket outlet larger than 1kA? Yep, sounds like it when the meter in question doesnt have the required specifications or ratings to safely withstand that much energy. This thread being about a meter that has a claimed CAT I, and joeqsmith saying it shouldn't be a problem for mains.

Or perhaps these gems from the 61010 standard:

for equipment marked with measurement category I, a warning shall be given not to use the equipment for measurements within measurement categories II, III and IV

Measurement category I is for measurements performed on circuits not directly connected to MAINS

[AVGresponding]

Fair enough. Which is why I would curious if any UK based electricians here could indicate what kind of prospective fault current would be measured at a typical UK 13 A wall socket? (It would be a range, obviously, but typical/min/max would be interesting.)

Wikipedia says typical UK ring circuits have 30A fuses and 2.5mm² cable.

Wikipedia needs editing... what a surprise! Any installation still using fuses would for sure be a Code 2 on an EICR, maybe a Code 1 if the sparky is in a bad mood (yes, there's some wiggle room). Most are going to be MCBs at the least, or RCDs or RCBOs. In any case, for domestic installs they'll be 32A type B, with a 6kA breaking capacity.
The 2.5mm² T+E has a CPC CSA of 1.5mm², and in a ring of course there's two paths back to the board (barring fault conditions).
Radials (for socket outlets) are in 4mm² which also has a 1.5mm² CPC (used to be 2.5mm², but hey, cost cutting), and will be protected by a 20A type B MCB/RCD/RCBO.

[Fungus]

Wikipedia needs editing... what a surprise! Any installation still using fuses would for sure be a Code 2 on an EICR, maybe a Code 1 if the sparky is in a bad mood (yes, there's some wiggle room). Most are going to be MCBs at the least, or RCDs or RCBOs. In any case, for domestic installs they'll be 32A type B, with a 6kA breaking capacity.
The 2.5mm² T+E has a CPC CSA of 1.5mm², and in a ring of course there's two paths back to the board (barring fault conditions).
Radials (for socket outlets) are in 4mm² which also has a 1.5mm² CPC (used to be 2.5mm², but hey, cost cutting), and will be protected by a 20A type B MCB/RCD/RCBO.

What it actually says is: " They are generally wired with 2.5 mm2 cable and protected by a 30 A fuse, an older 30 A circuit breaker, or a European harmonised 32 A circuit breaker. Sometimes 4 mm2 cable is used if very long cable runs"

But don't let your anti-Wikipedia bias get in your way.

[AVGresponding]

Wikipedia needs editing... what a surprise! Any installation still using fuses would for sure be a Code 2 on an EICR, maybe a Code 1 if the sparky is in a bad mood (yes, there's some wiggle room). Most are going to be MCBs at the least, or RCDs or RCBOs. In any case, for domestic installs they'll be 32A type B, with a 6kA breaking capacity.
The 2.5mm² T+E has a CPC CSA of 1.5mm², and in a ring of course there's two paths back to the board (barring fault conditions).
Radials (for socket outlets) are in 4mm² which also has a 1.5mm² CPC (used to be 2.5mm², but hey, cost cutting), and will be protected by a 20A type B MCB/RCD/RCBO.

What it actually says is: " They are generally wired with 2.5 mm2 cable and protected by a 30 A fuse, an older 30 A circuit breaker, or a European harmonised 32 A circuit breaker. Sometimes 4 mm2 cable is used if very long cable runs"

But don't let your anti-Wikipedia bias get in your way.

I like Wikipedia, and I fund it from time to time. The article header mentions it needs additional verification and citations, and this is a fair assessment. There is some ambiguity and misleading information in it. A circuit breaker old enough to be rated at 30A would be just as bad as a rewirable fuse, and would attract similar comments on an EICR; the tripping times on these old things are so slow as to be positively glacial. I can't recall ever seeing pyro used in a domestic setting. A consumer unit is not the same thing as a distribution board; all consumer units are distribution boards, but not all distribution boards are consumer units.

4mm² can be used for particularly long runs, but this is not ideal, and would be unlikely to be necessary in a domestic setting, and would be discouraged in any case, due to the negative impact on tripping times. I have seen 6mm² used on a 20A radial socket circuit; it barely passed muster under testing.
Normally these situations can be avoided by having a better design, ie by having a DB nearer to the load.

[IanB]

4mm2 can be used for particularly long runs, but this is not ideal, and would be unlikely to be necessary in a domestic setting, and would be discouraged in any case, due to the negative impact on tripping times. I have seen 6mm2 used on a 20A radial socket circuit; it barely passed muster under testing.

How and why does cable size affect tripping times? For example, a 12 m run of 6 mm2 is going to have the same resistance and voltage drop as an 8 m run of 4 mm2 or a 5 m run of 2.5 mm2. Run lengths are going to vary a lot between a large house and a small shed.

[themadhippy]

I have seen 6mm2 used on a 20A radial socket circuit; it barely passed muster under testing

how come? the R1 R2 for 6mm is going to be lower than the same length of a bit of 2.5/1.5,meaning your fault current will be higher leading to a faster disconnection time,the only failure i can think of is the fault current being  to high for the protective device

[AVGresponding]

4mm2 can be used for particularly long runs, but this is not ideal, and would be unlikely to be necessary in a domestic setting, and would be discouraged in any case, due to the negative impact on tripping times. I have seen 6mm2 used on a 20A radial socket circuit; it barely passed muster under testing.

How and why does cable size affect tripping times? For example, a 12 m run of 6 mm2 is going to have the same resistance and voltage drop as an 8 m run of 4 mm2 or a 5 m run of 2.5 mm2. Run lengths are going to vary a lot between a large house and a small shed.

You're thinking in terms of DC resistance; this is an AC circuit...

[AVGresponding]

I have seen 6mm2 used on a 20A radial socket circuit; it barely passed muster under testing

how come? the R1 R2 for 6mm is going to be lower than the same length of a bit of 2.5/1.5,meaning your fault current will be higher leading to a faster disconnection time,the only failure i can think of is the fault current being  to high for the protective device

It was a very long run. I can't remember the exact length (this was 10 years ago), but I remember expressing some doubt. Funnily enough I was in the building yesterday, doing some fire alarm and emergency lights testing.

It was for some sockets on columns, in a conference hall. They had to go up and over the ceiling, rather than in the floor; istr there were 4 columns and they used 2 circuits, so 2 columns per circuit. Only 2 double sockets per circuit, but the length would be over 60m I should think.

[IanB]

You're thinking in terms of DC resistance; this is an AC circuit...

The calculations for 50/60 Hz AC are the same as for DC where resistance, voltage drop and maximum fault currents are concerned.

[AVGresponding]

You're thinking in terms of DC resistance; this is an AC circuit...

The calculations for 50/60 Hz AC are the same as for DC where resistance, voltage drop and maximum fault currents are concerned.

The PFC is based on the impedance, not resistance, of the CPC.

As for RCD trip times, it's the capacitance of long cables that affects the trip time.