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Default Where does air come from in a sealed heating system?

I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?
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On 2/24/2017 11:47 AM, Tim Streater wrote:
In article , Adam Funk
wrote:

I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


Is it air? Or is it hydrogen? Try setting light to it as it hisses out.

In which case it comes from corrosion of the iron. I have never felt
confident enough to do this test; if there was air present as well
(entering system as dissolved air during a pressure top-up) there is a
theoretical risk of a hydrogen explosion.
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On 24/02/2017 11:32, Adam Funk wrote:
I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler,& find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


As others have said, it could be hydrogen - caused by corrosion. Is
there any corrosion inhibitor in your system?
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On 24/02/17 12:38, Chris Hogg wrote:
You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.


It won't - there's no O2 in the radiator to sustain combustion.
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"Tim Watts" wrote in message
...

On 24/02/17 12:38, Chris Hogg wrote:
You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.


It won't - there's no O2 in the radiator to sustain combustion.



Well there may be if there is air in there !

It IS possible for air to be drawn into a sealed system at loose compression
fittings on the suck side of the circulating pump, and those fittings not
leak out water in normal use - I've seen it, but it struck me as very odd at
the time.

Andrew



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On 2/24/2017 12:38 PM, Chris Hogg wrote:
On Fri, 24 Feb 2017 12:18:29 +0000, newshound
wrote:

On 2/24/2017 11:47 AM, Tim Streater wrote:
In article , Adam Funk
wrote:

I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?

Is it air? Or is it hydrogen? Try setting light to it as it hisses out.

In which case it comes from corrosion of the iron. I have never felt
confident enough to do this test; if there was air present as well
(entering system as dissolved air during a pressure top-up) there is a
theoretical risk of a hydrogen explosion.


You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.

I wondered that too, but do you feel lucky? Hydrogen is infamous for its
very wide explosive range compared to methane.
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In article ,
Adam Funk wrote:
I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.


I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


I've assumed it gets drawn in from a tiny leak somewhere when the system
cools down. Locally, there are going to be bits under negative pressure,
even when the system as a whole is slightly pressurised.

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The whole system is under pressure either from gravity or from a filling
loop. There is not really a "suck" side to the pump - it is a "circulator
rather than a positive displacement pump
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On 24/02/17 13:22, newshound wrote:
On 2/24/2017 12:38 PM, Chris Hogg wrote:

You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.

I wondered that too, but do you feel lucky? Hydrogen is infamous for its
very wide explosive range compared to methane.


Then just open the valve slightly and put a spot of diluted washing-up
liquid on the bleed point. Wait until a small bubble has formed, detach
it, and see what happens when you hold a flame to it.

--

Jeff
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In article 6,
DerbyBorn wrote:


The whole system is under pressure either from gravity or from a filling
loop. There is not really a "suck" side to the pump - it is a
"circulator rather than a positive displacement pump


Then air could never find its way in?

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Ho ho. Are you suggesting some kind of battery charger effect here? Besides
if there is hydrogen then there should also be oxygen. Not only that but
hydrogen is very good at finding its way out of sealed systems.
Brian

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"Tim Streater" wrote in message
.. .
In article , Adam Funk
wrote:

I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


Is it air? Or is it hydrogen? Try setting light to it as it hisses out.

--
"The problem with defending the purity of the English language is that
English
is about as pure as a cribhouse whore. We don't just borrow words; on
occasion,
English has pursued other languages down alleyways to beat them
unconscious and rifle their pockets for new vocabulary." --
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On 24/02/17 11:32, Adam Funk wrote:
I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler, & find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?

usually its not air, is hydrogen or hydrogen sulphide I think, Corrosion
products

--
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true: it is true because it is powerful."

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On 2017-02-24, Roger Mills wrote:

On 24/02/2017 11:32, Adam Funk wrote:
I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler,& find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


As others have said, it could be hydrogen - caused by corrosion. Is
there any corrosion inhibitor in your system?


The plumbers (who I think are very good) drained & power-flushed the
whole system in spring 2014 when they installed the new boiler, &
added corrosion inhibitor. They may have added inhibitor in spring
2015 when they serviced the boiler, & definitely added it when they
moved & replaced a radiator & serviced the boiler in spring 2016.
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On 24/02/17 16:11, Chris Hogg wrote:
On Fri, 24 Feb 2017 15:43:46 -0000, "Brian Gaff"
wrote:

Ho ho. Are you suggesting some kind of battery charger effect here? Besides
if there is hydrogen then there should also be oxygen. Not only that but
hydrogen is very good at finding its way out of sealed systems.
Brian

The oxygen is taken up by the iron in the radiators, especially if
they're new, aka rusting, leaving the hydrogen.

Fe + H2O - FeO + H2

Or if that doesn't work for you,

Eff ee plus aitch two oh gives eff ee oh plus aitch two

& F All else

--
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eventually come to believe it. The lie can be maintained only for such
time as the State can shield the people from the political, economic
and/or military consequences of the lie. It thus becomes vitally
important for the State to use all of its powers to repress dissent, for
the truth is the mortal enemy of the lie, and thus by extension, the
truth is the greatest enemy of the State.

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On 24/02/17 15:43, Brian Gaff wrote:
Ho ho. Are you suggesting some kind of battery charger effect here? Besides
if there is hydrogen then there should also be oxygen. Not only that but
hydrogen is very good at finding its way out of sealed systems.
Brian


No - the oxygen from the H2O molecule has combined with the iron to form
black iron oxide, thus releasing the now spare hydrogen.
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On Fri, 24 Feb 2017 15:34:11 +0000 (GMT), Dave Plowman (News) wrote:

The whole system is under pressure either from gravity or from a
filling loop. There is not really a "suck" side to the pump - it

is a
"circulator rather than a positive displacement pump


Then air could never find its way in?


With open vented with even a little bit of pump over it will.
Sealed system is trickier to get air in but the chances are it's not
air but hydrogen released when the iron grabs the oxygen from a water
molecule.

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On 24/02/2017 12:38, Chris Hogg wrote:

You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.


OK, you try it and we'll watch.

Bill
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Brian Gaff wrote

Water is strange stuff when its hot it expands and when its cold it
expands.


Yes, but that has nothing to do with the problem being discussed.

However there is always air in it, just more air in some bits and less in
others.


Yes, and like with any other solution, the amount of air
it can hold varys with the temperature of the water.

So I think the answer is that being lighter than water it takes some time
to get to a high point in the system where it gets trapped.


What actually happens is that water can hold less air at some
temperatures than others and once it comes out of the water
because it can't remain in the water, it accumulates in the high
points in the system where it can't get back into the water again.

Adam Funk wrote


I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the water
at the cold surface in the cistern, then come out of solution later in
the hot parts. But we have a sealed system (with a combination boiler)
now.


I'd also expect to get a bit of dissolved air (to come out later) in the
mains water when I add more to the system. But usually I bleed the two
radiators, check the pressure gauge on the boiler, & find I don't need to
add more water, but still find some air a week or two later. Where is it
coming from in that case?


Out of the water. There is nowhere else for it to come from.

Just more air from the previous top-up coming out a while later?


Yep.

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On 24/02/17 18:56, Bill Wright wrote:
On 24/02/2017 12:38, Chris Hogg wrote:

You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.


OK, you try it and we'll watch.


well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.

Thats why she had a coal range.


Bill



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On Sat, 25 Feb 2017 08:28:08 +0000, The Natural Philosopher
wrote:




well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.


Was she like mine mine and thought electricity leaked from lamp
sockets if there was no bulb in them ?


G.Harman
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On 25/02/17 15:57, Chris Hogg wrote:
On Sat, 25 Feb 2017 15:01:40 +0000, wrote:

On Sat, 25 Feb 2017 08:28:08 +0000, The Natural Philosopher
wrote:




well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.


Was she like mine mine and thought electricity leaked from lamp
sockets if there was no bulb in them ?


G.Harman


UR James Thurber AICMFP

https://todayinsci.com/T/Thurber_Jam...Quotations.htm

There are some who think that electricity from nuclear power stations
is radioactive. Perhaps that's why Harry is so keen on generating his
own!

All harry generates is biogas

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On Friday, February 24, 2017 at 4:45:05 PM UTC, Adam Funk wrote:
On 2017-02-24, Roger Mills wrote:

On 24/02/2017 11:32, Adam Funk wrote:
I keep finding air in the tops of the same two radiators. This made
sense in the old vented system, because air could dissolve into the
water at the cold surface in the cistern, then come out of solution
later in the hot parts. But we have a sealed system (with a
combination boiler) now.

I'd also expect to get a bit of dissolved air (to come out later) in
the mains water when I add more to the system. But usually I bleed
the two radiators, check the pressure gauge on the boiler,& find I
don't need to add more water, but still find some air a week or two
later. Where is it coming from in that case? Just more air from the
previous top-up coming out a while later?


As others have said, it could be hydrogen - caused by corrosion. Is
there any corrosion inhibitor in your system?


The plumbers (who I think are very good) drained & power-flushed the
whole system in spring 2014 when they installed the new boiler, &
added corrosion inhibitor. They may have added inhibitor in spring
2015 when they serviced the boiler, & definitely added it when they
moved & replaced a radiator & serviced the boiler in spring 2016.


Proper answer, some details mentioned by others.

Most probably hydrogen from electolytic/bi-metallic corrosion. That produces H2 & O2. The oxygen combines with the inside surface of your radiators to form magnetite sludge. Igniting it at the air vent is most unlikely to cause an explosion (I've never heard of that happening), but the recommended procedure is to bleed the gas into an upturned glass/bottle (H2 floats upwards) and then ignite that. You may otherwise have difficulty in closing the air vent after it has turned into a blow-torch (see Youtube).

If hydrogen, the gas in the upturned glass will light with a pop and burn upwards.

The important thing is that you'll usually only get the electrolytic/bi-metallic corrosion if the water is acidic. The acid usually gets in to the system as the residues from active flux (contains ammonium chloride, forms HCl on heating ISTR) that hasn't been thoroughly flushed out.

The French braze copper heating pipes (no flux needed); they have virtually no black sludge problems, there is no market for power-flushing in France.. Go figure.

It's been power-flushed. They will have used an acidic cleaner (HCl); that has to be flushed, neutralized (with caustic soda), flushed, checked with litmus paper (did you see that done?) and flushed again for good measure.

It might be air (nitrogen); that can get drawn into the system on the suction side of the pump, as mentioned elsewhere. The oxygen forms magnetite, as above. The expansion vessel connection (neutral point, PONPC) should be on the pump inlet side.

Most good domestic inhibitors (Sentinel, Fernox, etc) contain sodium molybdate; ISTR that the mixture is slightly acidic. I like to run a flushed system with clean water for a few hours, check it's not acidic, then add inhibitor.

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On Saturday, February 25, 2017 at 3:01:42 PM UTC, wrote:
On Sat, 25 Feb 2017 08:28:08 +0000, The Natural Philosopher
wrote:




well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.


Was she like mine mine and thought electricity leaked from lamp
sockets if there was no bulb in them ?


G.Harman


My Mum thought the electric leaked out of 3-pin sockets that were left switched on with nothing plugged in. I pointed out the little plastic shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.
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wrote in message
...
On Sat, 25 Feb 2017 08:28:08 +0000, The Natural Philosopher
wrote:




well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.


Was she like mine mine and thought electricity leaked from lamp
sockets if there was no bulb in them ?


Have you ever wondered if you ended up with those genes ?

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In article 6,
DerbyBorn writes:


The whole system is under pressure either from gravity or from a filling
loop. There is not really a "suck" side to the pump - it is a "circulator
rather than a positive displacement pump


The system contains pressurised water, but partial pressures of
oxygen and nitrogen in the water will be well below air pressure
when the system cools, so it will suck these gases in through any
small leaks, to dissolve in the cold water. When the water is
heated, the solubility of oxygen and nitrogen reduces and they'll
come out as gas bubbles and collect at high points. When temperature
drops again, the partial pressure of oxygen and nitrogen in the water
will drop, and it will suck in more to dissolve. It may seem strange
that air is passing through a leak in the opposite direction to the
water, but that's what happens.

In a heating system, the water leak may well not be noticable, as the
heat may dry the water as fast as it's leaking. To find it, wait
until you aren't using the heating and it stays cold, and then feel
around the pipework and radiator plugs for leaks. If it's a sealed
system, you might also increase the pressure to the normal hot
running pressure, to speed up any leak. (Remember to let it back down
to normal afterwards, and don't blow off the excess via the over-
pressure valve, as you might end up with dirt on the seat, which
makes it leak. Dried crystals on pipework/radiators can also be
a sign of a leak.

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On Sat, 25 Feb 2017 12:26:20 -0800 (PST), Onetap
wrote:



Was she like mine mine and thought electricity leaked from lamp
sockets if there was no bulb in them ?


G.Harman


My Mum thought the electric leaked out of 3-pin sockets that were left switched on with nothing plugged in. I pointed out the little plastic shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


As did my gran, I do wonder if people of her generation Born(1901)
thought electricity was like gas which could leak out of fittings if
they were turned on but not lit.
OTOH my Gran would hve been in here teens when she first met gas when
she went into service.

Normally she was fairly practical and had a grasp of mechanical things
as her father owned a couple of traction engines as an agricultural
contractor.
G.Harman


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On Sat, 25 Feb 2017 08:28:08 +0000, The Natural Philosopher
wrote:

On 24/02/17 18:56, Bill Wright wrote:
On 24/02/2017 12:38, Chris Hogg wrote:

You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.


OK, you try it and we'll watch.


well anyone who has a gas stove knows the danger that it will strike
back through the gas mains into he gasometer down the road and blow the
town up every time you want to boil a kettle.

Even my old gran knew that in 1955.

Thats why she had a coal range.


Bill

Er but the catalyst didn't come alonguntil the 60,s

It took Servotomic to make boiling a kettle slightly more dangerous
than being on a terrorist hit list.

As the saying went at the time "the IRA give warnings, Servotomic
don't"

AB

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Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were left
switched on with nothing plugged in. I pointed out the little plastic
shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.
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On Sun, 26 Feb 2017 09:46:13 +0000, Harry Bloomfield wrote:

Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were left
switched on with nothing plugged in. I pointed out the little plastic
shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.


I do the same. Goes back to the memory of what happened once when I
didn't switch off first (a story I have related before). 2kW electric
fire, 15 amp plug, DC mains.

Arc, nearby newspapers...

I know there's no need now, but the habit is ingrained.



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In message , Harry Bloomfield
writes
Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were
left switched on with nothing plugged in. I pointed out the little
plastic shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.


And quite right too. The switch contacts are designed to break the
current cleanly. The pin contacts may suffer a series of arcs leading to
pitting and degradation. In the worst case heating such that the
Beryllium copper contacts lose their *spring*.

Worst case is domestic staff switching off kettles by lifting the jug
from the base as you might from a kitchen range!

--
Tim Lamb
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In article ,
Harry Bloomfield wrote:
Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were left
switched on with nothing plugged in. I pointed out the little plastic
shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.


My father insisted a TV or radio etc was switched off first at its local
switch, then at the socket. And always both. But not unplugged. I did try
asking him why. ;-)

--
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Dave Plowman London SW
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On Sun, 26 Feb 2017 09:46:13 GMT, Harry Bloomfield wrote:

Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were left
switched on with nothing plugged in. I pointed out the little plastic
shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.


I try to switch off - had 2 plugs come apart at the 'seam', back in the
early days of 'slim' plugs and suffered grazes from the fuse holder. Seen a
couple more done by others.
Hasn't happened for about 30 years now, but...
--
Peter.
The gods will stay away
whilst religions hold sway
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On Sun, 26 Feb 2017 10:54:15 +0000, Tim Lamb wrote:

In message , Harry Bloomfield
writes
Onetap has brought this to us :
My Mum thought the electric leaked out of 3-pin sockets that were
left switched on with nothing plugged in. I pointed out the little
plastic shutters on the L & N pins that stopped the electric leaking out.

She grew up a long way from mains electricity.


My other half insists on turning the switch on a socket off, before
unplugging. She seems never to have come across unswitched 13amp socket
outlets.


And quite right too. The switch contacts are designed to break the
current cleanly. The pin contacts may suffer a series of arcs leading to
pitting and degradation. In the worst case heating such that the
Beryllium copper contacts lose their *spring*.

Worst case is domestic staff switching off kettles by lifting the jug
from the base as you might from a kitchen range!


Indeed - and with some things , using the switch on the socket is putting
the 'wear' on the cheapest part that is also easy to replace.
--
Peter.
The gods will stay away
whilst religions hold sway
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On 25/02/2017 20:12, Onetap wrote:
You may otherwise have difficulty in closing the air vent after it has turned into a blow-torch (see Youtube).


Blowtorch? How much gas is in there?

I can't find any scary videos. More gas lighter than blowtorch.

Andy
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Tim Lamb was thinking very hard :
And quite right too. The switch contacts are designed to break the current
cleanly. The pin contacts may suffer a series of arcs leading to pitting and
degradation. In the worst case heating such that the Beryllium copper
contacts lose their *spring*.


Were the sockets not designed to break the current, then all sockets
would be fitted with switches.

Worst case is domestic staff switching off kettles by lifting the jug from
the base as you might from a kitchen range!


I do that too. They have a switch in the base to swith the supply when
the kettle is lifted. Even if the base switch does eventually fail, by
then the kettle will need to be replaced. They are not expensive these
days.
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Harry Bloomfield wrote:

Tim Lamb wrote:

switching off kettles by lifting the jug from the base


They have a switch in the base to swith the supply when
the kettle is lifted.


Perhaps the older "jug" style ones with the connector at the back did (I
haven't got one left to check) but the more common ones now have a
coaxial connector, that's permanently live. Mine has a paddle switch on
the kettle itself, not sure if they all do?

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