When I've wired runs of 240v single phase 13A sockets in various buildings
on the farm I've always put them all on one phase so that there is no danger
of 415v phase to phase accidents when using things on leads - am I being
paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on opposite
walls 40 foot apart. It would be convenient to put them on different phases
not only to balance the load but also to free up a 'way' in the breaker box.
But this goes against my natural instinct.

...... what does the team think ?

Andrew

Well I can well remember many many years ago the factory I was working in
got a visit from the Electricity mob, as our new extension running soak
tests on colour tvs and with lots of Fluorescent lights was making a hole in
one phase. After much measuring and head scratching they did put different
parts of our factory on different phases at the Leccy folks expense.
I certainly do not recall anyone even mentioning the 440 volt issue,
though now you mention it I guess if you were really determined you could
achieve it!
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Andrew Mawson" wrote in message
news
When I've wired runs of 240v single phase 13A sockets in various buildings
on the farm I've always put them all on one phase so that there is no
danger of 415v phase to phase accidents when using things on leads - am I
being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a 'way'
in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

Andrew

Andrew Mawson wrote

When I've wired runs of 240v single phase 13A sockets in
various buildings on the farm I've always put them all on
one phase so that there is no danger of 415v phase to phase
accidents when using things on leads - am I being paranoid ?

Yep. I have outlets on more than phase on it works fine
when you lose just one phase, you don't lose everything.

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them
on different phases not only to balance the load but also to free up
a 'way' in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

It'll be fine, and there is no team.

On 10-Nov-17 8:22 AM, Andrew Mawson wrote:
When I've wired runs of 240v single phase 13A sockets in various
buildings on the farm I've always put them all on one phase so that
there is no danger of 415v phase to phase accidents when using things on
leads - am I being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a
'way' in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

My factories all had 13A sockets on different phases, as did the
headquarters of the Electricity Board I use to work for. The basic rule
was to ensure that there was at least 6ft 6in (2m) separation between
sockets on different phases. To avoid any doubt, the sockets were marked
with red, yellow or blue phase discs, as appropriate, on the wall beside
them. I suppose these days, they would be marked brown, black or grey.

--
--

Colin Bignell

"Andrew Mawson" wrote in message
news
When I've wired runs of 240v single phase 13A sockets in various buildings
on the farm I've always put them all on one phase so that there is no
danger of 415v phase to phase accidents when using things on leads - am I
being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a 'way'
in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

You are right to be cautious about sockets on different phases. If you can
be sure that appliances on two different phases will not be connected
together (eg if they touch) then you should be fine.

I remember when our server lab at work was rewired, they put each bench on a
different phase. Goodness knows why. There were big signs up saying don't
connect (eg by USB, Ethernet or RS232) devices that are plugged into
different benches - which was a confounded nuisance if the only spare socket
for a temporary appliance happens to be on a bench (phase) that's different
to the one of the computer that you want to plug the appliance into.

Obviously in normal circumstances it would be absolutely fine, but there was
always the "it will never happen" case of both appliances becoming live
(each on a different phase) at the same time. If 240V hurts like hell and
may be fatal, 415V will hurt more and be "even more fatal".

On Fri, 10 Nov 2017 08:22:54 +0000, Andrew Mawson wrote:

When I've wired runs of 240v single phase 13A sockets in various
buildings on the farm I've always put them all on one phase so that
there is no danger of 415v phase to phase accidents when using things on
leads - am I being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a
'way' in the breaker box.
But this goes against my natural instinct.

..... what does the team think ?

Andrew

At a previous house (in the late '70s but $DEITY knows when they were
installed) we had two electricity meters.

I have the impression that they were on different phases (something about
power cuts) but I could well be wrong.

I suppose it would be possible to have one side of the house on each
phase, or upstairs and downstairs, but I have no idea if this was the case
nor why there were two meters anyway.


Cheers


Dave R


--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

Grey, really?
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Nightjar" wrote in message
...
On 10-Nov-17 8:22 AM, Andrew Mawson wrote:
When I've wired runs of 240v single phase 13A sockets in various
buildings on the farm I've always put them all on one phase so that there
is no danger of 415v phase to phase accidents when using things on
leads - am I being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a 'way'
in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

My factories all had 13A sockets on different phases, as did the
headquarters of the Electricity Board I use to work for. The basic rule
was to ensure that there was at least 6ft 6in (2m) separation between
sockets on different phases. To avoid any doubt, the sockets were marked
with red, yellow or blue phase discs, as appropriate, on the wall beside
them. I suppose these days, they would be marked brown, black or grey.

--
--

Colin Bignell

Add to that our building at Racal also had 440v marine supply at a much
higher frequency provided by a large rotary converter in the utilities area
of the place. I bet that would hurt.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"NY" wrote in message
o.uk...
"Andrew Mawson" wrote in message
news
When I've wired runs of 240v single phase 13A sockets in various
buildings on the farm I've always put them all on one phase so that there
is no danger of 415v phase to phase accidents when using things on
leads - am I being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a 'way'
in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

You are right to be cautious about sockets on different phases. If you can
be sure that appliances on two different phases will not be connected
together (eg if they touch) then you should be fine.

I remember when our server lab at work was rewired, they put each bench on
a different phase. Goodness knows why. There were big signs up saying
don't connect (eg by USB, Ethernet or RS232) devices that are plugged into
different benches - which was a confounded nuisance if the only spare
socket for a temporary appliance happens to be on a bench (phase) that's
different to the one of the computer that you want to plug the appliance
into.

Obviously in normal circumstances it would be absolutely fine, but there
was always the "it will never happen" case of both appliances becoming
live (each on a different phase) at the same time. If 240V hurts like hell
and may be fatal, 415V will hurt more and be "even more fatal".

On Friday, 10 November 2017 11:48:23 UTC, NY wrote:
"Andrew Mawson" wrote in message
news
When I've wired runs of 240v single phase 13A sockets in various buildings
on the farm I've always put them all on one phase so that there is no
danger of 415v phase to phase accidents when using things on leads - am I
being paranoid ?

I'm currently wiring up a Tractor Shed with runs of 13A sockets on
opposite walls 40 foot apart. It would be convenient to put them on
different phases not only to balance the load but also to free up a 'way'
in the breaker box. But this goes against my natural instinct.

..... what does the team think ?

You are right to be cautious about sockets on different phases. If you can
be sure that appliances on two different phases will not be connected
together (eg if they touch) then you should be fine.

I remember when our server lab at work was rewired, they put each bench on a
different phase. Goodness knows why. There were big signs up saying don't
connect (eg by USB, Ethernet or RS232) devices that are plugged into
different benches - which was a confounded nuisance if the only spare socket
for a temporary appliance happens to be on a bench (phase) that's different
to the one of the computer that you want to plug the appliance into.

Obviously in normal circumstances it would be absolutely fine, but there was
always the "it will never happen" case of both appliances becoming live
(each on a different phase) at the same time. If 240V hurts like hell and
may be fatal, 415V will hurt more and be "even more fatal".

I can't think of any good reason why this would be a problem. Does
anyone worry about separating computer equipment that is connected
to a UPS from that which isn't. Depending on the type of UPS the
situation could be exactly equivalent.

John

In article ,
wrote:
Obviously in normal circumstances it would be absolutely fine, but
there was always the "it will never happen" case of both appliances
becoming live (each on a different phase) at the same time. If 240V
hurts like hell and may be fatal, 415V will hurt more and be "even
more fatal".

I can't think of any good reason why this would be a problem. Does
anyone worry about separating computer equipment that is connected to a
UPS from that which isn't. Depending on the type of UPS the situation
could be exactly equivalent.

How do you get 415v from a UPS?

--
*I wonder how much deeper the ocean would be without sponges*

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

On Friday, 10 November 2017 17:05:19 UTC, Dave Plowman (News) wrote:

How do you get 415v from a UPS?

The same way you get it from a 3-phase mains connection. If the UPS
output happens at some moment to be phase shifted by 120 degrees
relative to a nearby mains-powered device then the phase to phase
voltage will be 415V.

The chance of connecting yourself between two line connections in
a 3-phase mains system or in a mains plus UPS situation is vanishingly
small, so no need to worry in either case.

However, nobody seems to worry about UPSs but they do about 3-phase mains.

John

On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion was to
have three phase wired using three black cores!

SteveW

On Friday, 10 November 2017 19:00:30 UTC, wrote:
On Friday, 10 November 2017 17:05:19 UTC, Dave Plowman (News) wrote:

How do you get 415v from a UPS?

The same way you get it from a 3-phase mains connection. If the UPS
output happens at some moment to be phase shifted by 120 degrees
relative to a nearby mains-powered device then the phase to phase
voltage will be 415V.

The chance of connecting yourself between two line connections in
a 3-phase mains system or in a mains plus UPS situation is vanishingly
small, so no need to worry in either case.

However, nobody seems to worry about UPSs but they do about 3-phase mains.

John

2x UPSes can output 480v ac between them when mains power goes down. RCDs much reduce the shock risk.


NT

On Fri, 10 Nov 2017 14:28:55 -0800 (PST), wrote:

On Friday, 10 November 2017 19:00:30 UTC, wrote:
On Friday, 10 November 2017 17:05:19 UTC, Dave Plowman (News) wrote:

How do you get 415v from a UPS?

The same way you get it from a 3-phase mains connection. If the UPS
output happens at some moment to be phase shifted by 120 degrees
relative to a nearby mains-powered device then the phase to phase
voltage will be 415V.

The chance of connecting yourself between two line connections in
a 3-phase mains system or in a mains plus UPS situation is vanishingly
small, so no need to worry in either case.

However, nobody seems to worry about UPSs but they do about 3-phase mains.

John

2x UPSes can output 480v ac between them when mains power goes down. RCDs much reduce the shock risk.

NT

Just a tickle compared with the battery compartment of a 3-phase UPS at 420V
DC.
--
Peter.
The gods will stay away
whilst religions hold sway

Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

In article ,
Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

--
from KT24 in Surrey, England

On 11/11/2017 11:46, charles wrote:
In article ,
Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users all
airline pilots, train drivers or others known not to be colour-blind

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

On 11/11/2017 12:31, Robin wrote:
On 11/11/2017 11:46, charles wrote:
In article ,
Â*Â*Â* Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Â*Â* Brian

Yes, Grey. A compromise, as the original harmonization suggestion
was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users all
airline pilots, train drivers or others known not to be colour-blind

An electrician who is colour blind will presumably know it and use other
methods for identification, for the rest following a colour in and out
of junction boxes, isolators, etc. is the normal way.

SteveW

In article ,
Robin wrote:
On 11/11/2017 11:46, charles wrote:
In article ,
Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users all
airline pilots, train drivers or others known not to be colour-blind

One reason for the change from red for 'live' green for 'earth'

--
*The colder the X-ray table, the more of your body is required on it *

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

In article ,
"Brian Gaff" writes:
Add to that our building at Racal also had 440v marine supply at a much
higher frequency provided by a large rotary converter in the utilities area
of the place. I bet that would hurt.

We had that back when I worked at GEC Computers.
400Hz, IIRC, although I thought it was for air frames.

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

On 11/11/2017 13:49, Steve Walker wrote:
On 11/11/2017 12:31, Robin wrote:
On 11/11/2017 11:46, charles wrote:
In article ,
Â*Â*Â* Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Â*Â* Brian

Yes, Grey. A compromise, as the original harmonization suggestion
was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users
all airline pilots, train drivers or others known not to be colour-blind

An electrician who is colour blind will presumably know it and use other
methods for identification, for the rest following a colour in and out
of junction boxes, isolators, etc. is the normal way.



yes but I had in mind not cable but the "illuminated indicators"

In passing I'm not sure how many colour-blind electricians are trained
these days. The JIB used to require a medical certificate to show
"absence of colour blindness in order to carry out the role to the
degree necessary to ensure no impediment to safe working and in
accordance with disability discrimination law" which left me not much
wiser. Employers are under a duty to assess the risks of any employee
who works with colour coded stuff. I don't know about insurance for
self-employed sparks.


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

In article ,
Dave Plowman (News) wrote:
In article ,
Robin wrote:
On 11/11/2017 11:46, charles wrote:
In article ,
Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Brian

Yes, Grey. A compromise, as the original harmonization suggestion
was to have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users all
airline pilots, train drivers or others known not to be colour-blind

One reason for the change from red for 'live' green for 'earth'

before harmonization, Germany used red for earth! The point about the earth
wire is the sleeving is striped.

--
from KT24 in Surrey, England

In article ,
charles wrote:
One reason for the change from red for 'live' green for 'earth'

before harmonization, Germany used red for earth! The point about the
earth wire is the sleeving is striped.

They still do on cars. ;-)

Thing is that the inability to distinguish between red and green in poor
light is pretty common among males. But then with everything coming with a
fitted plug these days not the problem it once was.

--
*Strip mining prevents forest fires.

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

On 11/11/2017 14:50, Robin wrote:
On 11/11/2017 13:49, Steve Walker wrote:
On 11/11/2017 12:31, Robin wrote:
On 11/11/2017 11:46, charles wrote:
In article ,
Â*Â*Â* Bob Minchin wrote:
Steve Walker wrote:
On 10/11/2017 14:39, Brian Gaff wrote:
Grey, really?
Â*Â* Brian

Yes, Grey. A compromise, as the original harmonization suggestion
was to
have three phase wired using three black cores!

SteveW


Yes, an absolutely mad decision making it impossible to have any
illuminated indicators in the phase colours

how about 1, 2 & 3?

I thought colours ought not to be relied upon anyway - unless users
all airline pilots, train drivers or others known not to be colour-blind

An electrician who is colour blind will presumably know it and use
other methods for identification, for the rest following a colour in
and out of junction boxes, isolators, etc. is the normal way.



yes but I had in mind not cable but the "illuminated indicators"

Ah, fair enough. But each indicator should be labelled anyway. Coloured
indicators for each phase will still appear lit or not to a colour blind
person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and
red lights to be used for running and stopped. Many people are red/green
colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green
for running or open and red for stopped or closed. I wonder how many
operators are tested for colour blindness?

In passing I'm not sure how many colour-blind electricians are trained
these days.Â* The JIB used to require a medical certificate to show
"absence of colour blindness in order to carry out the role to the
degree necessary to ensure no impediment to safe working and in
accordance with disability discrimination law" which left me not much
wiser.Â* Employers are under a duty to assess the risks of any employee
who works with colour coded stuff.Â* I don't know about insurance for
self-employed sparks.

From the quick look that I've done. Good colour vision still seems to
be required for apprentices, but not for people who work as electricians
and may have gained qualifications and experience without being an
apprentice.

SteveW

On 11/11/2017 14:10, Andrew Gabriel wrote:
In article ,
"Brian Gaff" writes:
Add to that our building at Racal also had 440v marine supply at a much
higher frequency provided by a large rotary converter in the utilities area
of the place. I bet that would hurt.

We had that back when I worked at GEC Computers.
400Hz, IIRC, although I thought it was for air frames.

IIRC things like gyroscopes on post-war military planes ran on 400 Hz.
My father bought me one in the 1960's which ran off a 12 volt rotary
converter.

On 10/11/2017 14:25, David wrote:


At a previous house (in the late '70s but $DEITY knows when they were
installed) we had two electricity meters.

I have the impression that they were on different phases (something about
power cuts) but I could well be wrong.

I suppose it would be possible to have one side of the house on each
phase, or upstairs and downstairs, but I have no idea if this was the case
nor why there were two meters anyway.

Sounds more like Economy 7 to me

On 12/11/2017 22:20, Steve Walker wrote:
On 11/11/2017 14:50, Robin wrote:
On 11/11/2017 13:49, Steve Walker wrote:


Ah, fair enough. But each indicator should be labelled anyway. Coloured
indicators for each phase will still appear lit or not to a colour blind
person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and
red lights to be used for running and stopped. Many people are red/green
colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green
for running or open and red for stopped or closed. I wonder how many
operators are tested for colour blindness?


I was involved in the design of some new control kit in the 2000's and
the then mandatory Human Factors assessment lady more or less vetoed any
coloured lights.

On 12/11/2017 22:47, newshound wrote:
On 12/11/2017 22:20, Steve Walker wrote:
On 11/11/2017 14:50, Robin wrote:
On 11/11/2017 13:49, Steve Walker wrote:


Ah, fair enough. But each indicator should be labelled anyway.
Coloured indicators for each phase will still appear lit or not to a
colour blind person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and
red lights to be used for running and stopped. Many people are
red/green colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green
for running or open and red for stopped or closed. I wonder how many
operators are tested for colour blindness?


I was involved in the design of some new control kit in the 2000's and
the then mandatory Human Factors assessment lady more or less vetoed any
coloured lights.

She shouldn't have been doing. She should have been requiring other ways
that a colour blind person could get the information (such as
labelling), but not removing the best and quickest way for non-colour
blind operators to get that same information. A red/green indication can
be spotted from across the room, labelling and the like can't.

SteveW

"newshound" wrote in message
o.uk...
On 12/11/2017 22:20, Steve Walker wrote:
On 11/11/2017 14:50, Robin wrote:
On 11/11/2017 13:49, Steve Walker wrote:


Ah, fair enough. But each indicator should be labelled anyway. Coloured
indicators for each phase will still appear lit or not to a colour blind
person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and
red lights to be used for running and stopped. Many people are red/green
colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green for
running or open and red for stopped or closed. I wonder how many
operators are tested for colour blindness?


I was involved in the design of some new control kit in the 2000's and the
then mandatory Human Factors assessment lady more or less vetoed any
coloured lights.

Ah the standard "a few people can't do it so we'll drag everyone else down
to that level" approach of H&S, Human Factors, political correctness etc.
:-(

"Steve Walker" wrote in message
news
An electrician who is colour blind will presumably know it and use other
methods for identification, for the rest following a colour in and out
of junction boxes, isolators, etc. is the normal way.

[snip] Coloured indicators for each phase will still appear lit or not to
a colour blind person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green and red
lights to be used for running and stopped. Many people are red/green
colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green for
running or open and red for stopped or closed. I wonder how many operators
are tested for colour blindness?

In passing I'm not sure how many colour-blind electricians are trained
these days. The JIB used to require a medical certificate to show
"absence of colour blindness in order to carry out the role to the degree
necessary to ensure no impediment to safe working and in accordance with
disability discrimination law" which left me not much wiser. Employers
are under a duty to assess the risks of any employee who works with
colour coded stuff. I don't know about insurance for self-employed
sparks.


Before I went to university, I worked for a year off in a research chemistry
lab where they did a lot of colour chemistry. My boss was telling me about
my predecessor who kept getting results that no-one else could replicate. To
begin with, the lad was just asked to repeat his experiments and still he
was adamant about the colour changes that he saw. My boss decided to watch,
to see if the lad was doing something different. Just as they were about to
get to the colour-change part of the experiment, the lad said casually "I
*am* colour blind - does that matter?". Yes indeed it did matter: what the
student was recording as a yellow to green change was actually the expected
red to blue change.

As my boss was telling me this story, I thought he was going to say that the
lad didn't know he was colour blind and this was how he first discovered it,
but no - he already knew full well but didn't realise that it would be
critical when doing colour chemistry.

On Sunday, 12 November 2017 22:20:41 UTC, Steve Walker wrote:

Ah, fair enough. But each indicator should be labelled anyway. Coloured
indicators for each phase will still appear lit or not to a colour blind
person, so noworse for them than them all being white.


Not necessarily. I recently came across somebody who could not see red
at all. It was a sunny day and a glass ornament was casting a clear
spectrum on the wall. He pointed to the parts of the spectrum that he
could see. Red was simply not visible at all.

John

On 13/11/2017 08:54, NY wrote:
"newshound" wrote in message
o.uk...
On 12/11/2017 22:20, Steve Walker wrote:
On 11/11/2017 14:50, Robin wrote:
On 11/11/2017 13:49, Steve Walker wrote:


Ah, fair enough. But each indicator should be labelled anyway.
Coloured indicators for each phase will still appear lit or not to a
colour blind person, so noworse for them than them all being white.

Incidentally though, it is normal on many control panels for green
and red lights to be used for running and stopped. Many people are
red/green colour blind, so they have to look harder at labels.

On screen control systems often have devices or valves that are green
for running or open and red for stopped or closed. I wonder how many
operators are tested for colour blindness?


I was involved in the design of some new control kit in the 2000's and
the then mandatory Human Factors assessment lady more or less vetoed
any coloured lights.

Ah the standard "a few people can't do it so we'll drag everyone else
down to that level" approach of H&S, Human Factors, political
correctness etc. :-(

Not a few people -- around 1 in 12 men are red-green colour blind. I'm
not too severely affected, but I have great difficulty telling whether
an LED indicator is red, orange, yellow or green; though I can usually
see the change if I'm watching it. Flashing in a particular pattern
solves it.

Wiring serial comms 'D' connectors was always a bit of a challenge, too.

In article ,
wrote:
Not a few people -- around 1 in 12 men are red-green colour blind. I'm
not too severely affected, but I have great difficulty telling whether
an LED indicator is red, orange, yellow or green; though I can usually
see the change if I'm watching it. Flashing in a particular pattern
solves it.

Figure an optician friend quoted for the UK was 1 in 3 males with blue
eyes. Something to do with genes. May be different today.

--
*A computer once beat me at chess, but it was no match for me at kickboxing.

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