Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

On 31/07/2018 10:21, Scott wrote:
Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

One per circuit.

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

That's my understanding.

What I've yet to see is a cost/benefit analysis of requiring them for
domestic premises in (some or all) of the UK. And I won't hold my
breath. Despite being de facto tertiary legislation, changes to BS7671
don't have to bother with pettifogging little things like impact
assessments showing eg if we'll all need space for a CU twice the size
and four times the cost.

--
Robin
reply-to address is (intended to be) valid

On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to balance the currents correctly at the high frequencies arcs contain. AFDDs are just RCDs/RCBOs with less hf filtering.


NT

wrote:

RCDs are to some extent sensitive to arcing as they fail to balance
the currents correctly at the high frequencies arcs contain. AFDDs
are just RCDs/RCBOs with less hf filtering.
I read that (some?) AFDDs use microprocessors to recognise the signature
of an arc.

On 31/07/2018 10:56, Andy Burns wrote:
wrote:

RCDs are to some extent sensitive to arcing as they fail to balance
the currents correctly at the high frequencies arcs contain. AFDDs
are just RCDs/RCBOs with less hf filtering.
I read that (some?) AFDDs use microprocessors to recognise the signature
of an arc.

Indeed. Bloody complicated. See eg the (promotional!) Beama Guide to
Arc Fault Detection Devices (AFDD)

http://www.beama.org.uk/asset/D6E1ED...CA85BA77DEC2B/

What I've not seen is how they are tested after they are installed.


--
Robin
reply-to address is (intended to be) valid

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

If they were mandatory I suspect there would be a lot of AFDD nuisance
trip threads here.
--

Graham.
%Profound_observation%

On 31/07/2018 10:53, wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to balance the currents correctly at the high frequencies arcs contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)





--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 31/07/2018 11:09, Robin wrote:
On 31/07/2018 10:56, Andy Burns wrote:
wrote:

RCDs are to some extent sensitive to arcing as they fail to balance
the currents correctly at the high frequencies arcs contain. AFDDs
are just RCDs/RCBOs with less hf filtering.
I read that (some?) AFDDs use microprocessors to recognise the
signature of an arc.

Indeed.Â* Bloody complicated. See eg the (promotional!) Beama Guide to
Arc Fault Detection Devices (AFDD)

http://www.beama.org.uk/asset/D6E1ED...CA85BA77DEC2B/

What I've not seen is how they are tested after they are installed.

The installation instructions I have seen seem to suggest that pushing
the test button is all you can do.

BS EN 62606 (general requirements for AFDDs) gives quite elaborate tests
for the devices themselves to verify if they meet the required standard,
but these are not things one would typically want to deploy in the field
(e.g. use of sliding carbon rods setup as an arc generator, and a
guillotine type of mechanism designed to partially slice PVC flex to
create an arcing connection to one conductor and good connection to another)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 31 Jul 2018 12:42:11 +0100, John Rumm
wrote:

On 31/07/2018 11:09, Robin wrote:
On 31/07/2018 10:56, Andy Burns wrote:
wrote:

RCDs are to some extent sensitive to arcing as they fail to balance
the currents correctly at the high frequencies arcs contain. AFDDs
are just RCDs/RCBOs with less hf filtering.
I read that (some?) AFDDs use microprocessors to recognise the
signature of an arc.

Indeed.* Bloody complicated. See eg the (promotional!) Beama Guide to
Arc Fault Detection Devices (AFDD)

http://www.beama.org.uk/asset/D6E1ED...CA85BA77DEC2B/

What I've not seen is how they are tested after they are installed.

The installation instructions I have seen seem to suggest that pushing
the test button is all you can do.

BS EN 62606 (general requirements for AFDDs) gives quite elaborate tests
for the devices themselves to verify if they meet the required standard,
but these are not things one would typically want to deploy in the field
(e.g. use of sliding carbon rods setup as an arc generator, and a
guillotine type of mechanism designed to partially slice PVC flex to
create an arcing connection to one conductor and good connection to another)

Why would I be discouraged from doing this at home? Society has
become too risk averse :-)

On Tuesday, 31 July 2018 12:27:54 UTC+1, John Rumm wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to balance the currents correctly at the high frequencies arcs contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't filter hf out well enough.

The more complicated they get (microprocessor etc), the more likely they are to fail. But hopefully less nuisance trips - more than an RCD, but less than a cruder AFDD.


NT

On Tuesday, 31 July 2018 13:44:29 UTC+1, wrote:
The more complicated they get (microprocessor etc), the more likely they
are to fail.

The more likely they are to be hacked and the more attractive they are to counterfeit.

Admittedly when I cut through the cable in the bedroom ceiling there was quite a lot of arcing, and it was rather disconcerting seeing the sparks flying about overhead, and the 30A rewireable fuse didn't blow

Owain

On 31/07/2018 12:44, Scott wrote:
On Tue, 31 Jul 2018 12:42:11 +0100, John Rumm
wrote:

On 31/07/2018 11:09, Robin wrote:
On 31/07/2018 10:56, Andy Burns wrote:
wrote:

RCDs are to some extent sensitive to arcing as they fail to balance
the currents correctly at the high frequencies arcs contain. AFDDs
are just RCDs/RCBOs with less hf filtering.
I read that (some?) AFDDs use microprocessors to recognise the
signature of an arc.

Indeed.Â* Bloody complicated. See eg the (promotional!) Beama Guide to
Arc Fault Detection Devices (AFDD)

http://www.beama.org.uk/asset/D6E1ED...CA85BA77DEC2B/

What I've not seen is how they are tested after they are installed.

The installation instructions I have seen seem to suggest that pushing
the test button is all you can do.

BS EN 62606 (general requirements for AFDDs) gives quite elaborate tests
for the devices themselves to verify if they meet the required standard,
but these are not things one would typically want to deploy in the field
(e.g. use of sliding carbon rods setup as an arc generator, and a
guillotine type of mechanism designed to partially slice PVC flex to
create an arcing connection to one conductor and good connection to another)

Why would I be discouraged from doing this at home? Society has
become too risk averse :-)

By all means slice away... although I expect customers might be slight
wary when you take a stanley knife to their table lamp!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 31/07/2018 13:44, wrote:
On Tuesday, 31 July 2018 12:27:54 UTC+1, John Rumm wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to balance the currents correctly at the high frequencies arcs contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't filter hf out well enough.

Its often not even within the control of the RCD - there are usually
enough mains input suppressors with capacitors wired to earth, strewn
through an installation, that at elevated frequencies (or high harmonic
content) you can get genuine leakage to earth that the RCD will act on.
The only filtering you could do at the RCD would be temporal i.e. stick
a time delay in the response, but that is going to be counter productive
in a shock protection applications.

The more complicated they get (microprocessor etc), the more likely they are to fail. But hopefully less nuisance trips - more than an RCD, but less than a cruder AFDD.

I would expect the bits that tend to fail would be the caps - same as
they can in the analogue trigger circuits on RCDs. So you may not see
much difference in lifetime.

I am yet to be convinced that AFDD will have much impact in fire
reduction for domestic applications in the UK. I get the feeling that is
likely the view shared by the IET since they did not mandate them in
BS7671 - and appear to have only done the minimum necessary[1] to enact
the EU / CENELEC requirement.

[1] in fact its arguable that they have not actually even done that,
given the wording of the BS EN 62606 Doc: "This European Standard was
approved by CENELEC on 2013-08-13. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions
for giving this European Standard the status of a national standard
without any alteration."



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

wrote in message
...
On Tuesday, 31 July 2018 12:27:54 UTC+1, John Rumm wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to
balance the currents correctly at the high frequencies arcs contain.
AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't
filter hf out well enough.

The more complicated they get (microprocessor etc), the more likely they
are to fail.

Have fun explaining why that hasnt happened with cars.

But hopefully less nuisance trips - more
than an RCD, but less than a cruder AFDD.

On 31/07/2018 19:38, Rod Speed wrote:


wrote in message
...
On Tuesday, 31 July 2018 12:27:54 UTC+1, John RummÂ* wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, ScottÂ* wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the
current
may not exceed the rating (eg 32 amps).Â* Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to
balance the currents correctly at the high frequencies arcs
contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't
filter hf out well enough.

The more complicated they get (microprocessor etc), the more likely
they are to fail.

Have fun explaining why that hasnt happened with cars.

The vastly improved manufacturing techniques, designs, materials,
tolerances and even oils has reduced the failure rate of mechanical
parts enough to more than offset the increased failure rate of sensors,
electronic modules, etc. Not only do the electronics lead to a whole
host of failures, they are often difficult and expensive to diagnose and
frequently prohibitively expensive to repair.

SteveW

"Steve Walker" wrote in message
news
On 31/07/2018 19:38, Rod Speed wrote:


wrote in message
...
On Tuesday, 31 July 2018 12:27:54 UTC+1, John Rumm wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, Scott wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because
there
is no leakage to earth and would not trip a 'fuse' because the
current
may not exceed the rating (eg 32 amps). Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to
balance the currents correctly at the high frequencies arcs
contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency
is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't
filter hf out well enough.

The more complicated they get (microprocessor etc), the more likely they
are to fail.

Have fun explaining why that hasnt happened with cars.

The vastly improved manufacturing techniques, designs, materials,
tolerances and even oils has reduced the failure rate of mechanical parts

Didnt get anything like that with the 71 golf which has no computer
control.

enough to more than offset the increased failure rate of sensors,
electronic modules, etc.

Havent had a single failure of any of those in the now 12 year old Getz.

Not only do the electronics lead to a whole host of failures,

How odd that I havent had even a single failure in my now 12 year old Getz.

they are often difficult and expensive to diagnose

Even sillier than you usually manage when the ECM tells you when a sensor
has failed.

and frequently prohibitively expensive to repair.

How odd that I havent seen anyone have to dump
their car because it was too expensive to repair.

On Tuesday, 31 July 2018 20:02:51 UTC+1, Steve Walker wrote:
On 31/07/2018 19:38, Rod Speed wrote:
tabbypurr wrote in message
...
On Tuesday, 31 July 2018 12:27:54 UTC+1, John RummÂ* wrote:
On 31/07/2018 10:53, tabbypurr wrote:
On Tuesday, 31 July 2018 10:21:51 UTC+1, ScottÂ* wrote:

Following on from the thread on the 18th edition wiring regulations,
does anyone have any comments on whether these devices are a good
idea, or if they are more intended for industrial premises with
machinery running unattended?

Is it one per supply or one per circuit?

My assumption is that arcing would not trip an RCD/RCBO because there
is no leakage to earth and would not trip a 'fuse' because the
current
may not exceed the rating (eg 32 amps).Â* Is this broadly correct?

Almost. RCDs are to some extent sensitive to arcing as they fail to
balance the currents correctly at the high frequencies arcs
contain. AFDDs are just RCDs/RCBOs with less hf filtering.

Its true that an arc fault will trip some RCDs in some circumstances.
Although even in cases where you would expect a RCD to detect a fault -
say an arc fault to earth, they may fil to do so if the arc frequency is
significantly above 50Hz.

Most (all?) actual AFDDs contain an embedded microcontroller, and use
software to recognise the pattern of current spikes associated with
arcing. So technically a very different device from a typical RCD.
(although some makers may choose to package MCB/RCD functionality into
the same physical device)

FWIW I have a plug-in RCD that trips on L-N arcing. They just didn't
filter hf out well enough.

The more complicated they get (microprocessor etc), the more likely
they are to fail.

Have fun explaining why that hasnt happened with cars.

idiot

The vastly improved manufacturing techniques, designs, materials,
tolerances and even oils has reduced the failure rate of mechanical
parts enough to more than offset the increased failure rate of sensors,
electronic modules, etc. Not only do the electronics lead to a whole
host of failures, they are often difficult and expensive to diagnose and
frequently prohibitively expensive to repair.

SteveW

On Tuesday, 31 July 2018 20:44:04 UTC+1, Rod Speed wrote:

How odd that I havent seen anyone have to dump
their car because it was too expensive to repair.

I dunno what he's smoking but back into the idiot filter he goes

On Tue, 31 Jul 2018 06:19:12 -0700 (PDT),
wrote:

Admittedly when I cut through the cable in the bedroom ceiling there was
quite a lot of arcing, and it was rather disconcerting seeing the sparks flying about overhead, and the 30A rewireable fuse didn't blow

Takes a lot of sustained current to blow a 30 A wire fuse in a short
time. An MCB would have tripped using its magnetic rather than
thermal mechanisium.

Replacing wire fuses with MCBs is a good move and produces a
reduction in fires or WHY. RCDs are also a good move. But I can't
help thinking that AFD's are steeping over the line drawn by the Law
of Dimishing Returns, particulary on an installation protected by
MCBs/RCDs or RCBO's.

--
Cheers
Dave.

On 01/08/2018 11:22, Dave Liquorice wrote:
On Tue, 31 Jul 2018 06:19:12 -0700 (PDT),
wrote:

Admittedly when I cut through the cable in the bedroom ceiling there was
quite a lot of arcing, and it was rather disconcerting seeing the sparks flying about overhead, and the 30A rewireable fuse didn't blow

Takes a lot of sustained current to blow a 30 A wire fuse in a short
time. An MCB would have tripped using its magnetic rather than
thermal mechanisium.

Replacing wire fuses with MCBs is a good move and produces a
reduction in fires or WHY. RCDs are also a good move. But I can't
help thinking that AFD's are steeping over the line drawn by the Law
of Dimishing Returns, particulary on an installation protected by
MCBs/RCDs or RCBO's.

They may make more sense elsewhere in europe (where these "regs"
originated), where they may offer more protection for flexes supplied
from unfused plugs.

(and even more sense in places where Ali cables are used in domestic
settings).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wednesday, 1 August 2018 14:35:42 UTC+1, John Rumm wrote:
They may make more sense elsewhere ...

Like where USA-style pigtails and wirenuts are used.

Owain