The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.


#[nobody knows the history]
#
#I think I do. (some Brit in the know explained it to me long ago)
#The savings in copper is with respect to a hypothetical situation
#that never existed, and never came to be.
#(sorry this is really to technical and off topic for aue,
#but here we are)
#The idea was that Brits, forever shivering in their damp,
#uninsulated, solid stone walled houses you know,
#needed 5 kW electric heaters to get comfy.
#Now for 5 kW you need 30 A fuses,
#and for safety, having 30 A fuses requires 6 mm^2 wiring.
#(the heavy wire is needed because circuit resistance
#must be low enough to melt a fuse promtly, in case of a fault.)
#Fuses were the only safety available at the time.
#
#Now copper, for a star wiring in 6 mm^2,
#to wherever you may want heat
#was prohibitively expensive, by 1945 standards.
#So the bright idea was to have a ring of 2.5 mm^2 wire,
#fused with 30 A. This is fine if the ring is unbroken,
#with current to the fault going both ways.
#If the ring is interrupted you have a very dangerous situation:
#a short in effectively unprotected wiring.
#(2.5 mm^2 behind a 30 A fuse that requires 150 A to blow promptly)
#
#So it was decided to ameliorate that by having fused plugs as well,
#as back-up for the inherently unsafe main wiring,
#since the mains fuse can't be relied upon to cut out
#when an appliance is faulty.
#
#The sequel: the 5 kW heaters never materialized.
#(the impoverished Brits couldn't afford them,
# and the 'too cheap to meter' power never arrived)
#and Britain is stuck with an inherently unsafe wiring method
#that may actually waste copper.
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)
#
#It was a typical case of technocracy runnng wild,
#without informed public debate about the basic assumptions
#underlying it as feedback.
#More briefly, a muddle.

--
Mike Barnes

Mike Barnes wrote:

The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Snip ring final circuits.

The real reason for its allowance is probably from one of the Technical
Committees who had a long lunch, one of their members could make 2.5mm
T+E cheaply, and make a good profit on it, so he persuaded the others to
go along with it.
There is speculation on why we have the 5 seconds disconnection rule for
distribution circuits - far too long, and pretty unsafe if you drill
through it, and the usual answer is that there were so many fuses out
there, British manufacturing couldnt make a Breaker to meet the 0.4
second rule, so 5 seconds was standardied, hence the power companies
could continue to use their 100A fuses.

I know someone who is sitting on the Tech. Comm. re-writing Guidance
Note 3 (Inspection and Testing), and they say it is comical some of the
things that come up, there is little reasoning behind some of the
articles, yet "it has always been done that way, so why change it?"

As for the RFC, there was a large consultation about circuits a couple
of years ago, (it is all in a file on the IET site, though I cannot find
it now), with a long presentation why RFCs should be removed for the
2011 Amendment, this gave the pros and (mainly) cons for them, with
recommendations that they be removed from the standard circuit
definitions, and only used for certain applications.
The pro voice was heard after dinner, and the vote taken that things
should stay as they are. When reading the minutes, it is pretty clear
that there is a good case for removing them, but, cable makers sell more
cable for rings, so they have a bigger voice.

I've listened to a number of people who know the various writers of the
Tech. Documents, and there are very few good remarks about them, the
typical one being "out of touch" or "not open to reason".

Alan.

--
To reply by e-mail, change the ' + ' to 'plus'.

In article ,
Mike Barnes writes:
The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Well, there's a very tiny bit of truth, corrupted by gross
inaccuracies which could be a case of chinese whispers - gradual
corruption each time the story was retold.

Firstly, a "Ring Main" applies to electricity distribution in the
street to premises, and at a higher level, distribution between
areas. It is commonly incorrectly applied to the 30A/32A final
ring circuit in the home, which I assume is what was meant here.

The earlier wiring schemes used radial circuits with a 15A
socket on each radial circuit, back to a fuse in the fuse box.
Most rooms only had one 15A socket, so this was not too onerous.
Sometimes a 5A socket was also provided for light loads.
As electrical appliances grow in popularity, the idea of only
one socket in each room rapidly became unviable, but also the
idea of routing loads of 15A circuits back to the fusebox was
also not viable. It was recognised that you probably didn't need
more than 15A in a room (the room would get uncomfortably hot
if you did), but you might want to draw that load from anywhere
in the room, and indeed split it over multiple outlets. Thus
was born the (now obvious) idea of multiple socket outlets.

This was considered for some years pre-WWII, but implementation
came at the end of WWII when there was a shortage of copper.
This influenced the design which became the final ring circuit
we know today. The idea was to provide unlimited socket outlets,
but to recognise that only a certain amount of power was required
over any floor area, and not the maximum which each socket could
provide all at once. The design also allowed easy conversion from
15A radials to 30A ring circuit by reusing the same wire (although
that probably wasn't as common as had been envisaged). The design
included a move to a single socket type to handle everything, from
the horibble mixture of earlier 15A, 5A, 2A, 2- and 3-pin sockets
to make life much simpler.

I think it's a design which has lasted and worked very well.
There have been very few later corrections required (upping the
earth conductor size is the only one I can think of, apart from
a few safety improvements to the 13A plug). As such, the
opportunity to chuck out what we had before and start again
was a real benfit, and it was probably done at the last moment
it could have been before proliferation would have made any such
change impossible.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Mike Barnes wrote:
The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Well, for a start, 2.5mm cable arrived rather later - about 20 years
later. The originals used 7/029 cable.

And why would you want a 5 kW heater for localised - ie portable - use? 3
kW is enough for most rooms.

15 amp was the largest common socket size before rings.


Was this written by some US wag? The home of electrical fires cause by
their mickey mouse wiring? Wire nuts indeed - rightly banned here years
ago.

--
*Few women admit their age; fewer men act it.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" :
Was this written by some US wag?

Dutch, I believe.

--
Mike Barnes

"A.Lee" wrote in message
...
Mike Barnes wrote:

The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Snip ring final circuits.

The real reason for its allowance is probably from one of the Technical
Committees who had a long lunch, one of their members could make 2.5mm
T+E cheaply, and make a good profit on it, so he persuaded the others to
go along with it.
There is speculation on why we have the 5 seconds disconnection rule for
distribution circuits - far too long, and pretty unsafe if you drill
through it, and the usual answer is that there were so many fuses out
there, British manufacturing couldnt make a Breaker to meet the 0.4
second rule, so 5 seconds was standardied, hence the power companies
could continue to use their 100A fuses.

I know someone who is sitting on the Tech. Comm. re-writing Guidance
Note 3 (Inspection and Testing), and they say it is comical some of the
things that come up, there is little reasoning behind some of the
articles, yet "it has always been done that way, so why change it?"

As for the RFC, there was a large consultation about circuits a couple
of years ago, (it is all in a file on the IET site, though I cannot find
it now), with a long presentation why RFCs should be removed for the
2011 Amendment, this gave the pros and (mainly) cons for them, with
recommendations that they be removed from the standard circuit
definitions, and only used for certain applications.
The pro voice was heard after dinner, and the vote taken that things
should stay as they are. When reading the minutes, it is pretty clear
that there is a good case for removing them, but, cable makers sell more
cable for rings, so they have a bigger voice.

I've listened to a number of people who know the various writers of the
Tech. Documents, and there are very few good remarks about them, the
typical one being "out of touch" or "not open to reason".

Alan.

You can post stuff like that you will upset the people that don't understand
the cons, those people have a name.. electricians.

On Mar 9, 9:03*am, Mike Barnes wrote:
The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

#[nobody knows the history]

Its well enough known. Re other reasons why it was implemented, maybe
there were a few people that thought 5kW heaters and other such things
were a good reason to go with rings, but that wasnt the main reason.
Bear in mind that electric heating beyond a background level in the
40s was prohibitively expensive, so its not an idea that would have
had much support.


#I think I do. (some Brit in the know explained it to me long ago)
#The savings in copper is with respect to a hypothetical situation
#that never existed, and never came to be.
#(sorry this is really to technical and off topic for aue,
#but here we are)
#The idea was that Brits, forever shivering in their damp,
#uninsulated, solid stone walled houses you know,
#needed 5 kW electric heaters to get comfy.
#Now for 5 kW you need 30 A fuses,

5kW 240v = 21A


#and for safety, having 30 A fuses requires 6 mm^2 wiring.

21A requires 2.5sqmm
30A requires 4sqmm
http://wiki.diyfaq.org.uk/index.php?title=Cable


#(the heavy wire is needed because circuit resistance
#must be low enough to melt a fuse promtly, in case of a fault.)

2.5 sqmm doesnt prevent that happening


#Fuses were the only safety available at the time.

there was also earthing, thermal overcurrent breakers and various
other protections. Fuses totally dominated breakers for reasons of
cost & safety.

#Now copper, for a star wiring in 6 mm^2,
#to wherever you may want heat
#was prohibitively expensive, by 1945 standards.

yes

#So the bright idea was to have a ring of 2.5 mm^2 wire,
#fused with 30 A. This is fine if the ring is unbroken,
#with current to the fault going both ways.
#If the ring is interrupted you have a very dangerous situation:
#a short in effectively unprotected wiring.
#(2.5 mm^2 behind a 30 A fuse that requires 150 A to blow promptly)

not true
1. 2.5 sqmm rings do survive 30A fusing just fine, and operation at
well above 30A for limited times is part of the design and practice of
such circuits - bother 30A fused and 32A MCBed.
2. The added R of using 2.5sqmm does not cause a problem with a 30A
fuse blowing
3. 2.5sqmm ring is _much_ safer than 6mm radial under fault
conditions. Connection failures usually arent instant, they
deteriorate eg due to a screw loosening over time and copper
oxidising. In a radial circuit, fire is a likely result, rings
continue working without a hitch. And connection failures are common.


#So it was decided to ameliorate that by having fused plugs as well,
#as back-up for the inherently unsafe main wiring,
#since the mains fuse can't be relied upon to cut out
#when an appliance is faulty.

A 5kW plug fuse is no more reliable in tripping than a 5kW fixed
wiring fuse. In fact the CU fuse is quicker at tripping, because of
other loads also on the circuit, and again because of less likelihood
of abuse.

#The sequel: the 5 kW heaters never materialized.
#(the impoverished Brits couldn't afford them,
# and the 'too cheap to meter' power never arrived)
#and Britain is stuck with an inherently unsafe wiring method
#that may actually waste copper.

Rings are much safer and use less copper in the great majority of
domestic property layouts.
http://wiki.diyfaq.org.uk/index.php?...cuit#Criticism


#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads


#It was a typical case of technocracy runnng wild,
#without informed public debate about the basic assumptions
#underlying it as feedback.
#More briefly, a muddle.

Its more the sort stuff that is too much talked about ring circuits by
those that dont understand them. There's nothing glamorous about
them, but they have saved many lives due to their excellent tolerance
of poor connections, which are a fairly common occurrence.


NT

On Mar 9, 10:00*am, (A.Lee) wrote:
Mike Barnes wrote:
The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Snip ring final circuits.

The real reason for its allowance is probably from one of the Technical
Committees who had a long lunch, one of their members could make 2.5mm
T+E cheaply, and make a good profit on it, so he persuaded the others to
go along with it.
There is speculation on why we have the 5 seconds disconnection rule for
distribution circuits - far too long, and pretty unsafe if you drill
through it, and the usual answer is that there were so many fuses out
there, British manufacturing couldnt make a Breaker to meet the 0.4
second rule,

Its trivial to make a breaker that acts wthin 0.4 seconds. The
mechanism is the same as a relay. Its not done because its not
desirable, both rings and radials are intended to pass overcurrent for
short times because they're entirely capable of doing so, and it
significantly increases their utility.


so 5 seconds was standardied, hence the power companies
could continue to use their 100A fuses.

I know someone who is sitting on the Tech. Comm. re-writing Guidance
Note 3 (Inspection and Testing), and they say it is comical some of the
things that come up, there is little reasoning behind some of the
articles, yet "it has always been done that way, so why change it?"

As for the RFC, there was a large consultation about circuits a couple
of years ago, (it is all in a file on the IET site, though I cannot find
it now), with a long presentation why RFCs should be removed for the
2011 Amendment, this gave the pros and (mainly) cons for them, with
recommendations that they be removed from the standard circuit
definitions, and only used for certain applications.
The pro voice was heard after dinner, and the vote taken that things
should stay as they are. When reading the minutes, it is pretty clear
that there is a good case for removing them,

Why dont you enlighten us, and we'll see.

but, cable makers sell more
cable for rings, so they have a bigger voice.

I've listened to a number of people who know the various writers of the
Tech. Documents, and there are very few good remarks about them, the
typical one being "out of touch" or "not open to reason".

Alan.

NT wrote:

On Mar 9, 10:00 am, (A.Lee) wrote:

There is speculation on why we have the 5 seconds disconnection rule for
distribution circuits - far too long, and pretty unsafe if you drill
through it, and the usual answer is that there were so many fuses out
there, British manufacturing couldnt make a Breaker to meet the 0.4
second rule,

Its trivial to make a breaker that acts wthin 0.4 seconds. The
mechanism is the same as a relay. Its not done because its not
desirable, both rings and radials are intended to pass overcurrent for
short times because they're entirely capable of doing so, and it
significantly increases their utility.

As do Circuit Breakers. The point was, in the late 40's, British
manufacturing did not have the technology to make breakers at a
competitive price, so the fuse stayed as the main protection into the
80's, and is still the main protection for distribution boards.

so 5 seconds was standardied, hence the power companies
could continue to use their 100A fuses.

The pro voice was heard after dinner, and the vote taken that things
should stay as they are. When reading the minutes, it is pretty clear
that there is a good case for removing them,

Why dont you enlighten us, and we'll see.

A synopsis of it is he
http://www.google.co.uk/url?q=http:/...g/wiring-matte
rs/27/ring-circuit.cfm%3Ftype%3Dpdf&sa=U&ei=aiBaT5L-Os3m8QP9-pndDg&ved=0
CBkQFjAB&usg=AFQjCNG4mPYWY7FFtqVMluRlMzTm_o2_NQ

It gives the usual arguments. I was talking last week to an attendee of
that event, and he said the anti-rfc argument was far stronger, and
agreed by most people as sensible (they should not be used, apart from
specific applications) but dinner (or a break according to the
timetable) intervened, and it was agreed for no action, apart from the
ones at the bottom of the report.

The full report is available somewhere, though google has failed me.

Alan


--
To reply by e-mail, change the ' + ' to 'plus'.

In article
,
Owain wrote:
On Mar 9, 1:46 pm, NT wrote:
Bear in mind that electric heating beyond a background level in the
40s was prohibitively expensive, so its not an idea that would have
had much support.

But in the 1940s-50s most rooms were unheated anyway and 'central
heating' would probably have been run to about 16-17 degC rather than
the 21 degC + typical today. Most people sat in the lounge and
listened to the wireless whilst wearing sweaters, not spread
themselves all over the house in t-shirts.

Referring to Ministry of Works Technical Notes No. 4 (price sixpence
net):

In the average small house or flat not exceeding 1,000 sq ft in floor
area it is reasonable to assume that the maximum demand for uses other
than for fixed lighting and cooking will not be greater than 7 kW (30
amp) however many sockets are provided.

The table for locations/numbers of sockets shows:

living rooms - 3 (fire, lamp, radio & tv)
bedrooms - 2 (fire, lamp)
kitchen - 3 (fridge, washing machine, iron)

A typical 3 bed semi would therefore have 1 ring circuit and 15 socket
outlets.

I think I'm up to 24 in my lounge alone.

Our first house, bought in 1964, was the result of a division in 1946.
There were 4 power points; one in each bedroom and one in the kitchen.
There was also a lighting point in the living room. Nedless to say, my
first job was rewiring.

--
From KT24

Using a RISC OS computer running v5.18

On 9 Mar,
(A.Lee) wrote:

The real reason for its allowance is probably from one of the Technical
Committees who had a long lunch, one of their members could make 2.5mm
T+E cheaply, and make a good profit on it, so he persuaded the others to
go along with it.

There was no such thing as 2.5mm T&E in those days. The first 20-30 years of
domestic ring mains were wired with good old stranded tin plated 7/029 T&E
which is near 2.9mm T&E in this modern rubbish!

--
B Thumbs
Change lycos to yahoo to reply

wrote:

On 9 Mar,
(A.Lee) wrote:

The real reason for its allowance is probably from one of the Technical
Committees who had a long lunch, one of their members could make 2.5mm
T+E cheaply, and make a good profit on it, so he persuaded the others to
go along with it.

There was no such thing as 2.5mm T&E in those days. The first 20-30 years of
domestic ring mains were wired with good old stranded tin plated 7/029 T&E
which is near 2.9mm T&E in this modern rubbish!

Yes, I knew that, the argument is still the same, in that manufacturers
had more say than legislators/Standards Techs, so their views held sway.

Alan.

--
To reply by e-mail, change the ' + ' to 'plus'.

On 9 Mar,
(Andrew Gabriel) wrote:

I think it's a design which has lasted and worked very well.
There have been very few later corrections required (upping the
earth conductor size is the only one I can think of, apart from
a few safety improvements to the 13A plug).

Was it really necessary to increase the earth conductor size? It was only
needed in some cases where rewireable fuses were used. It may have been more
economical to have outlawed fusewire, requiring cartridge fuses and MCBs to
be used.

With Ed17 requirements for RCDs even fusewire would be adequate for the earth
wire. 8^|.

--
B Thumbs
Change lycos to yahoo to reply

On Mar 9, 3:35*pm, (A.Lee) wrote:
NT wrote:
On Mar 9, 10:00 am, (A.Lee) wrote:
There is speculation on why we have the 5 seconds disconnection rule for
distribution circuits - far too long, and pretty unsafe if you drill
through it, and the usual answer is that there were so many fuses out
there, British manufacturing couldnt make a Breaker to meet the 0.4
second rule,

Its trivial to make a breaker that acts wthin 0.4 seconds. The
mechanism is the same as a relay. Its not done because its not
desirable, both rings and radials are intended to pass overcurrent for
short times because they're entirely capable of doing so, and it
significantly increases their utility.

As do Circuit Breakers. The point was, in the late 40's, British
manufacturing did not have the technology to make breakers at a
competitive price, so the fuse stayed as the main protection into the
80's, and is still the main protection for distribution boards.

so 5 seconds was standardied, hence the power companies
could continue to use their 100A fuses.
The pro voice was heard after dinner, and the vote taken that things
should stay as they are. When reading the minutes, it is pretty clear
that there is a good case for removing them,

Why dont you enlighten us, and we'll see.

A synopsis of it is he
http://www.google.co.uk/url?q=http:/...g/wiring-matte
rs/27/ring-circuit.cfm%3Ftype%3Dpdf&sa=U&ei=aiBaT5L-Os3m8QP9-pndDg&ved=0
CBkQFjAB&usg=AFQjCNG4mPYWY7FFtqVMluRlMzTm_o2_NQ

It gives the usual arguments. I was talking last week to an attendee of

the usual ill considered arguments

that event, and he said the anti-rfc argument was far stronger, and
agreed by most people as sensible (they should not be used, apart from
specific applications) but dinner (or a break according to the
timetable) intervened, and it was agreed for no action, apart from the
ones at the bottom of the report.

The full report is available somewhere, though google has failed me.

Alan

On Mar 9, 4:16*pm, Owain wrote:
On Mar 9, 1:46*pm, NT *wrote:

Bear in mind that electric heating beyond a background level in the
40s was prohibitively expensive, so its not an idea that would have
had much support.

But in the 1940s-50s most rooms were unheated anyway and 'central
heating' would probably have been run to about 16-17 degC rather than
the 21 degC + typical today. Most people sat in the lounge and
listened to the wireless whilst wearing sweaters, not spread
themselves all over the house in t-shirts.

Referring to Ministry of Works Technical Notes No. 4 (price sixpence
net):

In the average small house or flat not exceeding 1,000 sq ft in floor
area it is reasonable to assume that the maximum demand for uses other
than for fixed lighting and cooking will not be greater than 7 kW (30
amp) however many sockets are provided.

The table for locations/numbers of sockets shows:

living rooms - 3 (fire, lamp, radio & tv)
bedrooms - 2 (fire, lamp)
kitchen - 3 (fridge, washing machine, iron)

A typical 3 bed semi would therefore have 1 ring circuit and 15 socket
outlets.

I think I'm up to 24 in my lounge alone.

Owain

Do you know the year of that booklet?


NT

In article ,
A.Lee wrote:
wrote:

On 9 Mar,
(A.Lee) wrote:

The real reason for its allowance is probably from one of the
Technical Committees who had a long lunch, one of their members
could make 2.5mm T+E cheaply, and make a good profit on it, so he
persuaded the others to go along with it.

There was no such thing as 2.5mm T&E in those days. The first 20-30
years of domestic ring mains were wired with good old stranded tin
plated 7/029 T&E which is near 2.9mm T&E in this modern rubbish!

Yes, I knew that, the argument is still the same, in that manufacturers
had more say than legislators/Standards Techs, so their views held sway.

Why would a manufacturer want a system which is *more* economical on cable
than the previous one?

--
*You're never too old to learn something stupid.

Dave Plowman London SW
To e-mail, change noise into sound.

On Mar 9, 5:56*pm, wrote:
Was it really necessary to increase the earth conductor size? It was only
needed in some cases where rewireable fuses were used. It may have been more
economical to have outlawed fusewire, requiring cartridge fuses and MCBs to
be used.

Committee members do not have to declare their commercial
interests :-)

A downside with ring final circuits is where a house is multiple
occupancy renters. It can be better to have 32A ring/radial for
kitchen, then 16/20A radials for each room. Likewise for disabled re
any important equipment.

The 32A ring final is much maligned, but does have many benefits.
- We have plug top fuses, but unfortunately lost arguably better round
pins
- It can serve a larger area, offers two paths to balance loads
although I suspect many unbalanced, two routes for CPC re lower EFLI
(& hence larger area served), more conductor CSA (5mm) than a 32A
radial (4mm) would afford, length not restricted re EFLI (4mm has
oddly 1.5mm CPC, ring has twin 1.5mm CPC).

The cost benefit was in fuseboard ways incidentally, not just ease of
new build installation. It made it cheaper for builders, put simply.

In article
,
js.b1 wrote:
The 32A ring final is much maligned

Only by foreigners who don't know what the f**k they're talking about. Not
by anyone using it for the purposes intended.

--
*i souport publik edekashun.

Dave Plowman London SW
To e-mail, change noise into sound.

On Mar 9, 5:56*pm, wrote:
Was it really necessary to increase the earth conductor size? It was only
needed in some cases where rewireable fuses were used. It may have been more
economical to have outlawed fusewire, requiring cartridge fuses and MCBs to
be used.

It was also with regard to length, even with MCBs.

Plenty of sparks ran 7/029 T&E with 30A fuses due to its current
carrying capacity being higher than 27A FTE-2.5. It is here where the
smaller CPC was distinctly skimpy despite the line & neutral
conductors being plenty beefy enough. Quite a few small kitchens got
30A in 7/029, better installs got much larger (probably as butyl began
to fade as PVC came in).

On Mar 9, 7:09*pm, "Dave Plowman (News)" wrote:
In article
,
* *js.b1 wrote:

The 32A ring final is much maligned

Only by foreigners who don't know what the f**k they're talking about. Not
by anyone using it for the purposes intended.

You mean that big-ass oil drum welder out back :-))))

On Fri, 9 Mar 2012 08:16:42 -0800 (PST)
Owain wrote:

Referring to Ministry of Works Technical Notes No. 4 (price sixpence
net):

In the average small house or flat not exceeding 1,000 sq ft in floor
area it is reasonable to assume that the maximum demand for uses other
than for fixed lighting and cooking will not be greater than 7 kW (30
amp) however many sockets are provided.

The table for locations/numbers of sockets shows:

living rooms - 3 (fire, lamp, radio & tv)
bedrooms - 2 (fire, lamp)
kitchen - 3 (fridge, washing machine, iron)

A typical 3 bed semi would therefore have 1 ring circuit and 15 socket
outlets.

That might have been the government's theory but my parents' typical
1950's spec built 3 bedroom semi had 5 sockets on the ring - and 3 of
those were on a couple of spurs.

--
Mike Clarke

A.Lee wrote:
Mike Barnes wrote:

The subject of British ring mains came up in another group
(alt.usage.english). When it was said that nobody really knew the
history, one contributor came up with this explanation, which I
reproduce here for your entertainment.

Snip ring final circuits.

As for the RFC, there was a large consultation about circuits a couple
of years ago, (it is all in a file on the IET site, though I cannot
find it now), with a long presentation why RFCs should be removed for
the 2011 Amendment, this gave the pros and (mainly) cons for them,
with recommendations that they be removed from the standard circuit
definitions, and only used for certain applications.

Part of this?

http://electrical.theiet.org/wiring-...t.cfm?type=pdf


--
Adam

Dave Plowman (News) wrote:

Why would a manufacturer want a system which is *more* economical on
cable than the previous one?

Because dennis was in charge of the sales department.

--
Adam

On Fri, 09 Mar 2012 13:46:33 -0000, NT wrote:

On Mar 9, 9:03 am, Mike Barnes wrote:
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Surely it would be best to do as they suggest and have 30A cable in a star topology. You could have as many sockets as you like on a single line of 30A cable. Yes I know it would cost a bit more, but if something gets disconnected, you have no connection, instead of half a connection.

--
http://petersparrots.com
http://petersphotos.com

I go fishing; I catch nothing. I go to orgies; I catch everything.

On Mar 9, 8:07*pm, "Lieutenant Scott" wrote:
Surely it would be best to do as they suggest and have 30A cable in a star topology. *You could have as many sockets as you like on a single line of 30A cable. *Yes I know it would cost a bit more, but if something gets disconnected, you have no connection, instead of half a connection.

It would probably cost about the same due to UK housing layout.

The 30A star hub could go under the hall floor (upstairs), with a run
to each room and drop to rooms below. Unfortunately it would require a
newly developed junction box using L-N-E bus-bars to handle 8-9x 4mm
sized cables. It would be useful for central inspection and testing,
but buried under a floorboard it could well end up forgotten and
screws can work loose.

Such "star spiders" are sometimes used for complex lighting circuits,
built up using modern enclosures and DIN rail terminals. Easy central
inspection and testing, neutral at every light switch etc.

Part of this?

http://electrical.theiet.org/wiring-...t.cfm?type=pdf

The detailed papers presented at the meeting also used to be available.
But the link in the footnote to the Wiki page
http://wiki.diyfaq.org.uk/index.php?title=Ring_circuit no longer takes
one to that paper and I cannot now find them (or the minutes of the
meeting) on the IET site or elsewhere. Can you or others work some
magic to make them appear again pl?
--
Robin
reply to address is (meant to be) valid

"NT" wrote in message
...

8

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.

Every connection in a ring is safety critical.
There wouldn't be any point in making them a ring if the joints weren't
safety critical.
Why bother testing them if they work properly and safely with faulty joints?


It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.

Why do rings need rules to prevent users putting large loads at one end of
the ring if they are more tolerant of large loads


Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Protects it from what?
Sure they will blow if you short the circuit but they don't stop the thing
from passing over current for long periods.



#It was a typical case of technocracy runnng wild,
#without informed public debate about the basic assumptions
#underlying it as feedback.
#More briefly, a muddle.

Its more the sort stuff that is too much talked about ring circuits by
those that dont understand them. There's nothing glamorous about
them, but they have saved many lives due to their excellent tolerance
of poor connections, which are a fairly common occurrence.

The problem with rings is they appear to work fine even when there are bad
connections.
The bad connections can exist for years without a user noticing.
Then they are less safe than a radial because the conductor is sized smaller
than the fuse.
Of course if you used a 20A breaker, as 2.5 mm radials do. the rings would
be somewhat safer as in a connection fault condition they revert to being a
2.5 mm radial. Unlike present rings that become a 2.5 mm radials with a 30A
fuse, which is not allowed as its unsafe.

Being as rings are seldom tested and as you say faults are a fairly common
occurrence I don't see how you can claim they are safe.


NT

dennis wrote:
The problem with rings is they appear to work fine even when
there are bad connections.

If you want to wire up your house with a rats' nest of radials
fed from a 100-way consumer unit, go ahead, there's nothing
stopping you, and the IEEE regs even tell you how to do it
safely. Me, I'll stick to feeding a single cable from the CU
around the house and back to the same CU outlet.

JGH

"jgharston" wrote in message
...
dennis wrote:
The problem with rings is they appear to work fine even when
there are bad connections.

If you want to wire up your house with a rats' nest of radials
fed from a 100-way consumer unit, go ahead, there's nothing
stopping you, and the IEEE regs even tell you how to do it
safely. Me, I'll stick to feeding a single cable from the CU
around the house and back to the same CU outlet.

Do you know what a modern radial is?

In article ,
writes:
On 9 Mar,
(Andrew Gabriel) wrote:

I think it's a design which has lasted and worked very well.
There have been very few later corrections required (upping the
earth conductor size is the only one I can think of, apart from
a few safety improvements to the 13A plug).

Was it really necessary to increase the earth conductor size? It was only
needed in some cases where rewireable fuses were used. It may have been more
economical to have outlawed fusewire, requiring cartridge fuses and MCBs to
be used.

Well, that was a way around it at the time to fix existing installations,
but 2.5mm T&E was changed to have a 1.5mm CPC, verses the original 1mm CPC.

With Ed17 requirements for RCDs even fusewire would be adequate for the earth
wire. 8^|.

Yes.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 09/03/2012 20:07, Lieutenant Scott wrote:
On Fri, 09 Mar 2012 13:46:33 -0000, NT wrote:

On Mar 9, 9:03 am, Mike Barnes wrote:
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Surely it would be best to do as they suggest and have 30A cable in a
star topology. You could have as many sockets as you like on a single
line of 30A cable.

A 30/32A radial is a "standard circuit", so nothing to stop you from
using it.

Its not commonly used since it required 4.0mm^2 T&E which is harder to
work with. That also only has a 1.5mm^2 CPC so disconnection times are
lengthened slightly. It does not perform as well as the ring circuit
under most of the more common fault conditions. In particular a high
impedance or broken earth connection can leave a section of the circuit
unprotected with no visible symptom. High impedance connections in the L
or N are more likely to cause more serious localised heating, since
there is no alternate conduction path. The radial performs better with a
completely disconnected L or N, since that will disable a section of the
circuit. With a ring you can get an unbalanced circuit and in theory
overload one of the cables. In traditional installations (cable in
masonry / plaster etc) this is a bit theoretical since the cable rating
for just a single length is not far off the circuit protective device
rating, but becomes more problematic with cables buried in insulation.

Yes I know it would cost a bit more, but if something
gets disconnected, you have no connection, instead of half a connection.

True, but its not the most likely fault.


--
Cheers,

John.

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

On Sat, 10 Mar 2012 00:44:52 -0000, John Rumm wrote:

On 09/03/2012 20:07, Lieutenant Scott wrote:
On Fri, 09 Mar 2012 13:46:33 -0000, NT wrote:

On Mar 9, 9:03 am, Mike Barnes wrote:
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Surely it would be best to do as they suggest and have 30A cable in a
star topology. You could have as many sockets as you like on a single
line of 30A cable.

A 30/32A radial is a "standard circuit", so nothing to stop you from
using it.

Its not commonly used since it required 4.0mm^2 T&E which is harder to
work with. That also only has a 1.5mm^2 CPC so disconnection times are
lengthened slightly. It does not perform as well as the ring circuit
under most of the more common fault conditions. In particular a high
impedance or broken earth connection can leave a section of the circuit
unprotected with no visible symptom. High impedance connections in the L
or N are more likely to cause more serious localised heating, since
there is no alternate conduction path. The radial performs better with a
completely disconnected L or N, since that will disable a section of the
circuit. With a ring you can get an unbalanced circuit and in theory
overload one of the cables. In traditional installations (cable in
masonry / plaster etc) this is a bit theoretical since the cable rating
for just a single length is not far off the circuit protective device
rating, but becomes more problematic with cables buried in insulation.

I see. Why are lighting circuits never rings, and why does the lighting wire sold in DIY stores always seem to be rated at 16 amps ish, while I've never seen a lighting circuit have a fuse/breaker of anything other than 5/6A.

--
http://petersparrots.com
http://petersphotos.com

When there's a will, I want to be in it!

On Sat, 10 Mar 2012 00:44:52 +0000, John Rumm
wrote:

On 09/03/2012 20:07, Lieutenant Scott wrote:
On Fri, 09 Mar 2012 13:46:33 -0000, NT wrote:

On Mar 9, 9:03 am, Mike Barnes wrote:
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Surely it would be best to do as they suggest and have 30A cable in a
star topology. You could have as many sockets as you like on a single
line of 30A cable.

A 30/32A radial is a "standard circuit", so nothing to stop you from
using it.

Its not commonly used since it required 4.0mm^2 T&E which is harder to
work with.

Mumble years ago I requested a 30/32A supply to a test bench. Our
internal power tech did it (in proper steel conduit) using stranded
4mm^2, which he reckoned was much easier to handle in conduit than
solid core.
I never did investigate what the composition of the stranded wire was
- probably a successor to 7/0.036.

--
Frank Erskine

On Sat, 10 Mar 2012 01:37:31 -0000, Frank Erskine wrote:

On Sat, 10 Mar 2012 00:44:52 +0000, John Rumm
wrote:

On 09/03/2012 20:07, Lieutenant Scott wrote:
On Fri, 09 Mar 2012 13:46:33 -0000, NT wrote:

On Mar 9, 9:03 am, Mike Barnes wrote:
#(you could save copper and gain safety
#by leaving out part of the ring, and by using the two halves
#as branches of a star, fused with 2x16A instead of 1x30A)

That would make every connection in the circuit safety critical. A
single bad conection then risks fire or shock, soemthing that doesnt
occur with rings.
It also reduces the utility of the system, since each circuit is less
tolerant of large combination loads.
Finally it offers zero safety advantage. 30A fusing protects the ring
circuit itself fine, and plug fuses protect the appliances and their
leads

Surely it would be best to do as they suggest and have 30A cable in a
star topology. You could have as many sockets as you like on a single
line of 30A cable.

A 30/32A radial is a "standard circuit", so nothing to stop you from
using it.

Its not commonly used since it required 4.0mm^2 T&E which is harder to
work with.

Mumble years ago I requested a 30/32A supply to a test bench. Our
internal power tech did it (in proper steel conduit) using stranded
4mm^2, which he reckoned was much easier to handle in conduit than
solid core.
I never did investigate what the composition of the stranded wire was
- probably a successor to 7/0.036.

Solid core seems a little silly really. One strand, easier to break? Stiffer, harder to bend round corners? Point?

--
http://petersparrots.com
http://petersphotos.com

The only substitute for good manners is fast reflexes.

On 09/03/2012 20:53, Robin wrote:

The detailed papers presented at the meeting also used to be available.
But the link in the footnote to the Wiki page
http://wiki.diyfaq.org.uk/index.php?title=Ring_circuit no longer takes
one to that paper and I cannot now find them (or the minutes of the
meeting) on the IET site or elsewhere. Can you or others work some
magic to make them appear again pl?

VoilÃ*: http://www.maxwell.myzen.co.uk/uk.d-i-y/rings/

The history paper (David Latimer) is far and away the most interesting
(IMHO).

--
Andy

Lieutenant Scott wrote:

I see. Why are lighting circuits never rings, and why does the
lighting wire sold in DIY stores always seem to be rated at 16 amps
ish, while I've never seen a lighting circuit have a fuse/breaker of
anything other than 5/6A.

The point of the ring is to allow 20A cable to form a circuit that safely
uses a 32A MCB.

There would be no point in doing that is you were using 16A cable with a 6A
MCB

10A is probably the largest size MCB you will see in a house for the lights.
You might see 16A used in factories etc. BTW it's not 16A lighting cable,
look at

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes



--
Adam

In article ,
Frank Erskine wrote:

[Snip]

Mumble years ago I requested a 30/32A supply to a test bench. Our
internal power tech did it (in proper steel conduit) using stranded
4mm^2, which he reckoned was much easier to handle in conduit than
solid core.

When metric size cables firsta ppeared on the market they had solid core.
Even 2.5mm was a b****** to pull through conduit. Then the manufacturers
saw sense and provided a stranded version.


I never did investigate what the composition of the stranded wire was
- probably a successor to 7/0.036.

Funny that how 4mm (or 25mm) is made up is never stated - as it was
pre=metrication.

--
From KT24

Using a RISC OS computer running v5.18

Voilà: http://www.maxwell.myzen.co.uk/uk.d-i-y/rings/

Merci beaucoup.

The history paper (David Latimer) is far and away the most interesting
(IMHO).

Yes; and I am reminded how much I enjoyed the author's style (including
in the last paragraph (para. 12.1) where
it seems to me he gently injects the thought that if imitation is the
sincerest form of flattery then ......).

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

On Sat, 10 Mar 2012 07:54:28 -0000, ARWadsworth wrote:

Lieutenant Scott wrote:

I see. Why are lighting circuits never rings, and why does the
lighting wire sold in DIY stores always seem to be rated at 16 amps
ish, while I've never seen a lighting circuit have a fuse/breaker of
anything other than 5/6A.

The point of the ring is to allow 20A cable to form a circuit that safely
uses a 32A MCB.

There would be no point in doing that is you were using 16A cable with a 6A
MCB

I suppose you could use even thinner wire.

10A is probably the largest size MCB you will see in a house for the lights.
You might see 16A used in factories etc. BTW it's not 16A lighting cable,
look at

http://wiki.diyfaq.org.uk/index.php?...es#Cable_Sizes

Ah so 16A becomes 8A in insulation. Doesn't that mean we should be using huge cables for ring mains?

--
http://petersparrots.com
http://petersphotos.com

Gary Glitter has said if he gets executed he wants cremating and his ashes putting in an etch-a-sketch, so the kids can still play with him!

In article op.waxjnajcytk5n5@i7-940,
Lieutenant Scott wrote:
I see. Why are lighting circuits never rings, and why does the lighting
wire sold in DIY stores always seem to be rated at 16 amps ish, while
I've never seen a lighting circuit have a fuse/breaker of anything other
than 5/6A.

Lighting circuits are a fixed load - near enough. The idea of a final ring
circuit is that you don't have fixed loads in all of the sockets all the
time. If you do - like say in a kitchen - it's best to calculate the
actual load and make sure the ring is adequate.

--
*"I am " is reportedly the shortest sentence in the English language. *

Dave Plowman London SW
To e-mail, change noise into sound.