I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

"Tough Guy no. 1265" wrote in message
news
I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply



Not from me.

--
Adam

On Sat, 07 Nov 2015 16:50:11 -0000, ARW wrote:

"Tough Guy no. 1265" wrote in message
news
I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

Not from me.

You don't have a sensible opinion?!? :-)

--
Maybe "god" doesn't really care about religions, which were, after all, created by men... just like "god" was.

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

On Sat, 07 Nov 2015 18:14:59 -0000, harry wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at all. Most shocks are an exposed live to an earth, isolating the mains would remove that possibility altogether, and not change the amount of shocks between live and neutral.

--
H lp! S m b d st l ll th v w ls fr m m k yb rd!

On Saturday, November 7, 2015 at 4:42:25 PM UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

Because mains is an AC system, there is no such thing as a totally isolated system. There is always some capacitance between the conductors and earth which all adds up.

On Sat, 07 Nov 2015 19:12:57 -0000, wrote:

On Saturday, November 7, 2015 at 4:42:25 PM UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

Because mains is an AC system, there is no such thing as a totally isolated system. There is always some capacitance between the conductors and earth which all adds up.

Why do builders have isolating transformers then?

--
"I must take every precaution not to get pregnant," said Judi to her best friend Monika.
"But I thought you said your hubby had a vasectomy," Monika responded.
"He did. That's why I have to take every precaution!" shrieked Judi.

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?


Accepted convention is that the body of an article should include the information in the Subject. Note that writing "I'm asking the question at the top" takes more effort that duplicating the subject by copy'n'paste. Also, the question was never at the *top* here and is at present not displayed.

"Isolated mains voltage - why not as standard?"
=============================================

The supply under the street, or equivalent, is three-phase. Three adjacent houses will normally be on three different live phases, with a common neutral. Less copper is buried that way.

Providing an isolated voltage would require a power transformer for each property, or a multi-secondary one for each small group of properties, since a supply cannot be guaranteed to be isolated in property A if it is in full parallel with property B.

If an isolated supply is connected to equipment which generated a higher voltage internally, such as a CRT needs, then an internal fault could raise the floating supply to a high voltage, which would be dangerous throughout the premises.

Persons who think they have a need for an isolated supply can, with due care for the Building Regulations, use an isolating transformer where required..

--
(c) Dr. S. Lartius, UK. Gmail: dr.s.lartius@

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

On Saturday, 7 November 2015 19:13:00 UTC, wrote:

Because mains is an AC system, there is no such thing as a totally isolated
system. There is always some capacitance between the conductors and earth
which all adds up.

That is true. My mother once acquired a standard lamp with a hollow metal post. My brother wired it up, and it worked. When I arrived, I could feel the electricity on the post, which was probably at about 120V through of the order of maybe 100pF. I forget what cable he used; but I ensured that she had a three-core cable with all three cores connected as they should be.

--
(c) Dr. S. Lartius, UK. Gmail: dr.s.lartius@

On Sat, 07 Nov 2015 19:36:23 -0000, wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?


Accepted convention is that the body of an article should include the information in the Subject. Note that writing "I'm asking the question at the top" takes more effort that duplicating the subject by copy'n'paste. Also, the question was never at the *top* here and is at present not displayed.

It's in the subject.

"Isolated mains voltage - why not as standard?"
=============================================

The supply under the street, or equivalent, is three-phase. Three adjacent houses will normally be on three different live phases, with a common neutral. Less copper is buried that way.

I just drew a simple diagram with a substation at the West end of a street, followed by three houses moving East, on phase 1, 2, and 3.
Both the existing system and the isolated system all use the same amount of copper, as the neutral still goes to all the houses. The only difference is whether the neutral is lashed to the ground in the substation. Eg. my house has two conductors coming to it - live and neutral/earth. The only way that the existing system would use less copper than the isolated system is if the neutral was not in the wire, but relied on the ground to carry it from the house's earth rod to the substation's earth rod. This isn't done, the neutral conductor is always laid.

Providing an isolated voltage would require a power transformer for each property, or a multi-secondary one for each small group of properties, since a supply cannot be guaranteed to be isolated in property A if it is in full parallel with property B.

What do you mean by this? Are you taking about property A and B being on different phases? What is the problem?

If an isolated supply is connected to equipment which generated a higher voltage internally, such as a CRT needs, then an internal fault could raise the floating supply to a high voltage, which would be dangerous throughout the premises.

Impossible for three reasons:
1) How would a circuit be able to pump a higher voltage back into what is supplying it with energy?
2) There is so much current available from a substation, that it would clamp it to 240 volts.
3) If it was possible, then it could also happen with a non-isolated system.

Persons who think they have a need for an isolated supply can, with due care for the Building Regulations, use an isolating transformer where required.

Since builders use them, isolating transformers clearly make things safer, so I see no need to pay attention to any regulations.

--
There once was a time when all people believed in god and the church ruled. This time was called the Dark Ages. -- Richard Lederer

On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it does remove the shock from live to ground, which is more likely as only one conductor has to be touched.

--
Love is complicated machinery.
But sometimes all you need is a good screw to fix it.

On Sat, 07 Nov 2015 19:38:55 -0000, Chris Hogg wrote:

On Sat, 07 Nov 2015 19:27:07 -0000, "Tough Guy no. 1265"
wrote:

On Sat, 07 Nov 2015 19:12:57 -0000, wrote:

On Saturday, November 7, 2015 at 4:42:25 PM UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply

--
It said, "Insert disk #3," but only two will fit!

Because mains is an AC system, there is no such thing as a totally isolated system. There is always some capacitance between the conductors and earth which all adds up.

Why do builders have isolating transformers then?

And electric shaver sockets in bathrooms? I would think they're just a
small version of whole-house isolation?

Perhaps it's just because it's always been done that way, and that way
is cheaper than having a beefy transformer in every garage.

The substation could isolate. Just don't clamp neutral to the ground. 4 wires come out of the secondary side of the substation transformer, leave them away from the ground, and take them to the houses as normal.

--
Q: Why can't you have a Jewish Morris dancer?
A: Because you have to be a complete prick to be a Morris dancer.

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

On 07/11/2015 20:01, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 19:38:55 -0000, Chris Hogg wrote:

On Sat, 07 Nov 2015 19:27:07 -0000, "Tough Guy no. 1265"
wrote:

On Sat, 07 Nov 2015 19:12:57 -0000,
wrote:

On Saturday, November 7, 2015 at 4:42:25 PM UTC, Tough Guy no. 1265
wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

Because mains is an AC system, there is no such thing as a totally
isolated system. There is always some capacitance between the
conductors and earth which all adds up.

Why do builders have isolating transformers then?

And electric shaver sockets in bathrooms? I would think they're just a
small version of whole-house isolation?

Perhaps it's just because it's always been done that way, and that way
is cheaper than having a beefy transformer in every garage.

The substation could isolate. Just don't clamp neutral to the ground.
4 wires come out of the secondary side of the substation transformer,
leave them away from the ground, and take them to the houses as normal.

Do you understand about 3-phase distribution?

If you don't clamp neutral to ground, what do you think will happen to
each phase voltage wrt ground?

230V is enough for me!

On Sat, 07 Nov 2015 20:05:02 -0000, Fredxxx wrote:

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

But the two faults would have to be within reach of each other, eg your washing machine and your fridge both having a fault with the opposite conductor, and you touch both. So very unlikely.

Besides, I've never actually observed a fault where the chassis becomes live. The only shocks I've ever had were worn cables on a mower, touching a switch with wet hands when outside, etc. Now if the supply had been isolated, I wouldn't have received a shock.

--
23% of all photocopier faults worldwide are caused by people sitting on them and photocopying their buttocks.

Tough Guy no. 1265 wrote:

Why do builders have isolating transformers then?

They have transformers at 55 volt per side, so a typical fault would
only give you a 55 volt belt.
It isnt the isolation that is the main safety factor, it is the lower
voltage. I dont think all site transformers are isolating anyway -
bathroom shaver sockets are, but 110V plugs have an earth connection.
Either way, you are only getting 55volts if touching one live and earth,
so should survive getting a belt off one.
--
Alan
To reply by mail, change '+' to 'plus'

On Sat, 07 Nov 2015 20:13:05 -0000, Fredxxx wrote:

On 07/11/2015 20:01, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 19:38:55 -0000, Chris Hogg wrote:

On Sat, 07 Nov 2015 19:27:07 -0000, "Tough Guy no. 1265"
wrote:

On Sat, 07 Nov 2015 19:12:57 -0000,
wrote:

On Saturday, November 7, 2015 at 4:42:25 PM UTC, Tough Guy no. 1265
wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

Because mains is an AC system, there is no such thing as a totally
isolated system. There is always some capacitance between the
conductors and earth which all adds up.

Why do builders have isolating transformers then?

And electric shaver sockets in bathrooms? I would think they're just a
small version of whole-house isolation?

Perhaps it's just because it's always been done that way, and that way
is cheaper than having a beefy transformer in every garage.

The substation could isolate. Just don't clamp neutral to the ground.
4 wires come out of the secondary side of the substation transformer,
leave them away from the ground, and take them to the houses as normal.

Do you understand about 3-phase distribution?

If you don't clamp neutral to ground, what do you think will happen to
each phase voltage wrt ground?

230V is enough for me!

If isolated, no phase has any voltage with respect to ground, just like a battery sitting on your desk has no voltage with respect to ground.

--
Statistics show that 25% of all women are on medication for mental illness.
That's scary! It means 75% are running around with no bloody medication at all!!!

On Sat, 07 Nov 2015 20:19:27 +0000, Tough Guy no. 1265 wrote:

Besides, I've never actually observed a fault where the chassis becomes
live. The only shocks I've ever had were worn cables on a mower,
touching a switch with wet hands when outside, etc. Now if the supply
had been isolated, I wouldn't have received a shock.

Naw, you want an RCD for that, mate.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it
does remove the shock from live to ground, which is more likely as only
one conductor has to be touched.

But the cost of a ****ing great transformer for the entire house
and the losses involved in that don't warrant the tiny increase
safety. Makes more sense to use RCDs and double insulated
smaller appliances instead.

On Sat, 07 Nov 2015 20:20:06 +0000, A.Lee wrote:

They have transformers at 55 volt per side, so a typical fault would
only give you a 55 volt belt.

55V doesn't constitute a "belt" in my book. Can't feel anything at all
below 80V; that's the point when I first feel a slight tingle.

On Sat, 07 Nov 2015 20:00:21 +0000, Tough Guy no. 1265 wrote:

On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it
does remove the shock from live to ground, which is more likely as only
one conductor has to be touched.

Er, that's what I said.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:05:02 -0000, Fredxxx wrote:

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

But the two faults would have to be within reach of each other, eg your
washing machine and your fridge both having a fault with the opposite
conductor, and you touch both. So very unlikely.

Not as unlikely with a couple of small appliances in the kitchen.

Besides, I've never actually observed a fault where the chassis becomes
live.

Doesn't matter what you have observed, the design
of the system has to allow for that situation.

The only shocks I've ever had were worn cables on a mower, touching a
switch with wet hands when outside, etc.

A wire does come adrift inside an appliance quite a bit.

Now if the supply had been isolated, I wouldn't have received a shock.

But at the very high cost of a transformer for the entire house.

No thanks, RCDs and double insulated appliances makes a lot more sense.

On Sat, 07 Nov 2015 20:23:54 -0000, Cursitor Doom wrote:

On Sat, 07 Nov 2015 20:19:27 +0000, Tough Guy no. 1265 wrote:

Besides, I've never actually observed a fault where the chassis becomes
live. The only shocks I've ever had were worn cables on a mower,
touching a switch with wet hands when outside, etc. Now if the supply
had been isolated, I wouldn't have received a shock.

Naw, you want an RCD for that, mate.

Which wouldn't be needed if they simply removed the earth from the neutral. And remember RCDs never used to exist.

--
Lord, grant me the serenity to accept the things I cannot change,
the courage to change the things I can,
and the wisdom to hide the bodies of those people I had to kill because they ****ed me off.

On Sat, 07 Nov 2015 20:28:36 -0000, Rod Speed wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it
does remove the shock from live to ground, which is more likely as only
one conductor has to be touched.

But the cost of a ****ing great transformer for the entire house
and the losses involved in that don't warrant the tiny increase
safety. Makes more sense to use RCDs and double insulated
smaller appliances instead.

No more transformers required, simply have the output of the substation not connected to ground. That's actually LESS wiring.

--
We've had a hot, dry summer this year. It was so hot that one of my neighbors said his wife even thawed out.

On Sat, 07 Nov 2015 20:20:06 -0000, wrote:

Tough Guy no. 1265 wrote:

Why do builders have isolating transformers then?

They have transformers at 55 volt per side, so a typical fault would
only give you a 55 volt belt.
It isnt the isolation that is the main safety factor, it is the lower
voltage. I dont think all site transformers are isolating anyway -
bathroom shaver sockets are, but 110V plugs have an earth connection.
Either way, you are only getting 55volts if touching one live and earth,
so should survive getting a belt off one.

And if they were isolated, you'd get no belt at all, so not jump and fall off your ladder.

Anyway, every time I've seen one of those yellow builders transformers for sale, it's referred to as isolating.

--
They have Mother's day for Mother's and Father's day for Father's -- so what do they have for Single Men?
Palm Sunday

On Sat, 07 Nov 2015 20:33:24 -0000, Cursitor Doom wrote:

On Sat, 07 Nov 2015 20:00:21 +0000, Tough Guy no. 1265 wrote:

On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it
does remove the shock from live to ground, which is more likely as only
one conductor has to be touched.

Er, that's what I said.

You were taking about sensitive equipment, I was talking about people.

--
Why is the front of an aeroplane called a cockpit?
If you have female pilots do you call it a pussypit?

On Sat, 07 Nov 2015 20:33:48 -0000, Rod Speed wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:05:02 -0000, Fredxxx wrote:

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

But the two faults would have to be within reach of each other, eg your
washing machine and your fridge both having a fault with the opposite
conductor, and you touch both. So very unlikely.

Not as unlikely with a couple of small appliances in the kitchen.

I have never had ONE appliance get live on its chassis, nevermind two.

Besides, I've never actually observed a fault where the chassis becomes
live.

Doesn't matter what you have observed, the design
of the system has to allow for that situation.

Why allow for a remote possibility, thereby creating a very likely one of live to the ground?

The only shocks I've ever had were worn cables on a mower, touching a
switch with wet hands when outside, etc.

A wire does come adrift inside an appliance quite a bit.

No, because they are inside and don't get touched.

--
Computers can never replace human stupidity.

On Sat, 07 Nov 2015 21:24:24 +0000, Tough Guy no. 1265 wrote:

Which wouldn't be needed if they simply removed the earth from the
neutral. And remember RCDs never used to exist.

What are you going to do about safe tea? You'll have no earth on your
metal cabinets.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:23:54 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 20:19:27 +0000, Tough Guy no. 1265 wrote:

Besides, I've never actually observed a fault where the chassis becomes
live. The only shocks I've ever had were worn cables on a mower,
touching a switch with wet hands when outside, etc. Now if the supply
had been isolated, I wouldn't have received a shock.

Naw, you want an RCD for that, mate.

Which wouldn't be needed if they simply removed the earth from the
neutral.

Wrong. You can still get killed with that config.

And remember RCDs never used to exist.

Irrelevant to what makes sense now that they do.

On Sat, 07 Nov 2015 21:33:34 -0000, Cursitor Doom wrote:

On Sat, 07 Nov 2015 21:24:24 +0000, Tough Guy no. 1265 wrote:

Which wouldn't be needed if they simply removed the earth from the
neutral. And remember RCDs never used to exist.

What are you going to do about safe tea? You'll have no earth on your
metal cabinets.

Exactly, no earth to be leaning against when I accidentally touch the live on a damaged cable etc, which wouldn't matter anyway because the live would have no voltage WRT ground.

Isolated mains IMPROVES safe tea.

--
"An abstract noun," the teacher said, "is something you can think of, but you can't touch it. Can you give me an example of one?"
"Sure," a teenage boy replied. "My father's new car."

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:28:36 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to remove
the Earth reference. It prevents ground loops arising which can destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But it
does remove the shock from live to ground, which is more likely as only
one conductor has to be touched.

But the cost of a ****ing great transformer for the entire house
and the losses involved in that don't warrant the tiny increase
safety. Makes more sense to use RCDs and double insulated
smaller appliances instead.

No more transformers required,

Wrong.

simply have the output of the substation not connected to ground.

Wouldn't stop people getting electrocuted.

That's actually LESS wiring.

Wrong again.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:33:48 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:05:02 -0000, Fredxxx wrote:

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each
of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

But the two faults would have to be within reach of each other, eg your
washing machine and your fridge both having a fault with the opposite
conductor, and you touch both. So very unlikely.

Not as unlikely with a couple of small appliances in the kitchen.

I have never had ONE appliance get live on its chassis,

It happens anyway.

nevermind two.

You don't need two, in fact two would be safe. The problem is with
one with a live case and all the others with an earthed case and other
earthed stuff like the sink etc.

Besides, I've never actually observed a fault where the chassis becomes
live.

Doesn't matter what you have observed, the design
of the system has to allow for that situation.

Why allow for a remote possibility, thereby creating a very likely one of
live to the ground?

The only shocks I've ever had were worn cables on a mower, touching a
switch with wet hands when outside, etc.

A wire does come adrift inside an appliance quite a bit.

No,

Yep.

because they are inside and don't get touched.

They touch the case and that is a problem.

They come adrift when the wire comes out of what its
supposed to be attached to and when cord anchor isn't
good enough and some fool lets it fall off the bench
and hang on the cord etc.

On Sat, 07 Nov 2015 21:46:51 -0000, Rod Speed wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:23:54 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 20:19:27 +0000, Tough Guy no. 1265 wrote:

Besides, I've never actually observed a fault where the chassis becomes
live. The only shocks I've ever had were worn cables on a mower,
touching a switch with wet hands when outside, etc. Now if the supply
had been isolated, I wouldn't have received a shock.

Naw, you want an RCD for that, mate.

Which wouldn't be needed if they simply removed the earth from the
neutral.

Wrong. You can still get killed with that config.

But in half the number of ways.

And remember RCDs never used to exist.

Irrelevant to what makes sense now that they do.

RCDs are a nuisance. I would never install one in my house.

--
Alfred Hitchcock didn't have a belly button.

On Sat, 07 Nov 2015 21:52:56 -0000, Rod Speed wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:33:48 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news On Sat, 07 Nov 2015 20:05:02 -0000, Fredxxx wrote:

On 07/11/2015 19:07, Tough Guy no. 1265 wrote:
On Sat, 07 Nov 2015 18:14:59 -0000, harry
wrote:

On Saturday, 7 November 2015 16:42:25 UTC, Tough Guy no. 1265 wrote:
I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...e-mains-supply


--
It said, "Insert disk #3," but only two will fit!

It is important when electrical equipment/appliances have metal
cabinets which can be earthed. Which was everything years ago.
Without an earth, ant fault to the cabinet could not be detected and
would be dangerous if there were other earth faults.
Also get over certain capacitance effects.

Two faults is unlikely. One fault would of course not shock you at
all. Most shocks are an exposed live to an earth, isolating the mains
would remove that possibility altogether, and not change the amount of
shocks between live and neutral.

I would agree with you, but only if you can automatically detect each
of
the faults and interrupt the power accordingly.

An isolation transformer might well hide some faults as well as
introducing some more and so be more dangerous in reality than the
conventional single phase supply.

But the two faults would have to be within reach of each other, eg your
washing machine and your fridge both having a fault with the opposite
conductor, and you touch both. So very unlikely.

Not as unlikely with a couple of small appliances in the kitchen.

I have never had ONE appliance get live on its chassis,

It happens anyway.

Not as often as other problems.

nevermind two.

You don't need two, in fact two would be safe. The problem is with
one with a live case and all the others with an earthed case and other
earthed stuff like the sink etc.

No, because with isolation you don't have earths everywhere. You'd have to therefore have two faults, one with live to chassis and one with neutral to chassis.

Besides, I've never actually observed a fault where the chassis becomes
live.

Doesn't matter what you have observed, the design
of the system has to allow for that situation.

Why allow for a remote possibility, thereby creating a very likely one of
live to the ground?

The only shocks I've ever had were worn cables on a mower, touching a
switch with wet hands when outside, etc.

A wire does come adrift inside an appliance quite a bit.

No,

Yep.

because they are inside and don't get touched.

They touch the case and that is a problem.

They come adrift when the wire comes out of what its
supposed to be attached to and when cord anchor isn't
good enough and some fool lets it fall off the bench
and hang on the cord etc.

Usually the cord then yanks out the other conductors and live and neutral short, blowing the fuse.

--
What's the difference between PMS and Mad Cow Disease?
The number of tits.

Cursitor Doom wrote:
On Sat, 07 Nov 2015 20:00:21 +0000, Tough Guy no. 1265 wrote:

On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to
remove the Earth reference. It prevents ground loops arising which
can destroy sensitive test equipment. But an IT won't save you from
a belt if you somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical.
But it does remove the shock from live to ground, which is more
likely as only one conductor has to be touched.

Er, that's what I said.

Why are you feeding phucker?
All this dick wants is an argument.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 21:48:17 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:28:36 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom

wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to
remove
the Earth reference. It prevents ground loops arising which can
destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But
it
does remove the shock from live to ground, which is more likely as
only
one conductor has to be touched.

But the cost of a ****ing great transformer for the entire house
and the losses involved in that don't warrant the tiny increase
safety. Makes more sense to use RCDs and double insulated
smaller appliances instead.

No more transformers required,

Wrong.

simply have the output of the substation not connected to ground.

Wouldn't stop people getting electrocuted.

Yes it would, because the live has no voltage WRT ground anymore.

Wrong when its done at the substation for hundreds of houses.

That's actually LESS wiring.

Wrong again.

Same number of cables coming to each house, count them.

Same number isn't LESS wiring, stupid.

"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 21:46:51 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 20:23:54 -0000, Cursitor Doom
wrote:

On Sat, 07 Nov 2015 20:19:27 +0000, Tough Guy no. 1265 wrote:

Besides, I've never actually observed a fault where the chassis
becomes
live. The only shocks I've ever had were worn cables on a mower,
touching a switch with wet hands when outside, etc. Now if the
supply
had been isolated, I wouldn't have received a shock.

Naw, you want an RCD for that, mate.

Which wouldn't be needed if they simply removed the earth from the
neutral.

Wrong. You can still get killed with that config.

But in half the number of ways.

Wrong when its done at the substation.

There might just be a reason why no one does it that way world wide.

And remember RCDs never used to exist.

Irrelevant to what makes sense now that they do.

RCDs are a nuisance. I would never install one in my house.

You're free to be as stupid as you like. Sooner fools like you die the
better.

On Sat, 07 Nov 2015 22:52:34 -0000, Rod Speed wrote:



"Tough Guy no. 1265" wrote in message
news
On Sat, 07 Nov 2015 21:48:17 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news On Sat, 07 Nov 2015 20:28:36 -0000, Rod Speed
wrote:



"Tough Guy no. 1265" wrote in message
news On Sat, 07 Nov 2015 19:37:55 -0000, Cursitor Doom

wrote:

On Sat, 07 Nov 2015 16:42:20 +0000, Tough Guy no. 1265 wrote:

I looked this up, I'm asking the question at the top. The replies
don't
seem to be able to agree. Any sensible opinions?

http://electronics.stackexchange.com...hy-are-we-not-
always-isolating-the-mains-supply

In repair & testing scenarios, we use isolation transformers to
remove
the Earth reference. It prevents ground loops arising which can
destroy
sensitive test equipment. But an IT won't save you from a belt if you
somehow manage to bridge directly across it.

No it won't, but it won't make it any worse, it'll be identical. But
it
does remove the shock from live to ground, which is more likely as
only
one conductor has to be touched.

But the cost of a ****ing great transformer for the entire house
and the losses involved in that don't warrant the tiny increase
safety. Makes more sense to use RCDs and double insulated
smaller appliances instead.

No more transformers required,

Wrong.

simply have the output of the substation not connected to ground.

Wouldn't stop people getting electrocuted.

Yes it would, because the live has no voltage WRT ground anymore.

Wrong when its done at the substation for hundreds of houses.

Explain.

That's actually LESS wiring.

Wrong again.

Same number of cables coming to each house, count them.

Same number isn't LESS wiring, stupid.

No grounding point required.

--
A female friend of mine was admitted to a private hospital to try to
lose weight. Naturally I sent her flowers.

I received a "thank-you" note several days later; it said, "Thanks for
the flowers, they were delicious!"

On Sat, 07 Nov 2015 21:47:18 +0000, Tough Guy no. 1265 wrote:

Isolated mains IMPROVES safe tea.

I suppose these days with more and more STUFF coming in double-insulated
plastic encapsulations, there may be SOME merit to your argument. We'll
just prematurely scrap all the metal-cased appliances, then. Happy?