OT -- switching heating elements

[Jeffrey Angus]

On 6/20/2011 7:16 PM, William Sommerwerck wrote:

Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V" source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

And try not to obscure the issue by arguing about 240 volts
being a source or not. It the measured voltage between a
specific pair of 120 volt sources adds up to 240 volts, it's
a 240 volt source. Period. None of your pedantic weaseling
around is going to change that.

Jeff



--
"Everything from Crackers to Coffins"

 

[William Sommerwerck]

"Jeffrey Angus" <jangus@suddenlink.net> wrote in message
news:itoujq$dr4$1@dont-email.me...

Damn you are fucking dense William.
The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

The oven was fixed Saturday.

Why don't you stop by, and I'll pull out the heating element part way. Then
you can touch one of the wires feeding the element with one hand, and the a
ground (such as the oven cabinet) with your other other hand.

Care to bet your life on it?

I didn't think so.

 

[Jeffrey Angus]

On 6/20/2011 10:36 PM, William Sommerwerck wrote:

Why don't you stop by, and I'll pull out the heating element part way. Then
you can touch one of the wires feeding the element with one hand, and the a
ground (such as the oven cabinet) with your other other hand.

Care to bet your life on it?

I'd be happy to idiot. I have enough sense to disconnect it first.

Jeff



--
"Everything from Crackers to Coffins"

 

[William Sommerwerck]

"Jeffrey Angus" <jangus@suddenlink.net> wrote in message
news:itp42h$858$1@dont-email.me...

On 6/20/2011 10:36 PM, William Sommerwerck wrote:

Why don't you stop by, and I'll pull out the heating element part way.
Then you can touch one of the wires feeding the element with one hand,
and the a ground (such as the oven cabinet) with your other other hand.

Care to bet your life on it?

I'd be happy to, idiot. I have enough sense to disconnect it first.

Oh. I thought all that was needed was to disconnect one side.

From my perspective, the issue is this... There are certain design rules you
follow, simply because they're common sense. That's it.

My toaster oven doesn't shut off when you open the door, either because B&D
was cheap, or the designer didn't think anything bad would ever happen.
Older models did, including ones with sealed heating elements.

 

[Jeffrey Angus]

On 6/21/2011 7:25 AM, William Sommerwerck wrote:

"Jeffrey Angus"<jangus@suddenlink.net> wrote in message
news:itp42h$858$1@dont-email.me...
On 6/20/2011 10:36 PM, William Sommerwerck wrote:

Why don't you stop by, and I'll pull out the heating element part way.
Then you can touch one of the wires feeding the element with one hand,
and the a ground (such as the oven cabinet) with your other other hand.

Care to bet your life on it?

I'd be happy to, idiot. I have enough sense to disconnect it first.

Oh. I thought all that was needed was to disconnect one side.

Uh huh, you're purposely talking in circles here....

You only have to disconnect one side to make the heater not heat.
You have to disconnect BOTH sides to make sure it's doesn't have
power on it to safely service the unit.

From my perspective, the issue is this... There are certain design rules you
follow, simply because they're common sense. That's it.

My toaster oven doesn't shut off when you open the door, either because B&D
was cheap, or the designer didn't think anything bad would ever happen.
Older models did, including ones with sealed heating elements.

Does you gas oven shut it self off when you open the door?

What kind of red herring is this? It's a fucking toaster oven, not
a front loading washing machine.

Jeff



--
"Everything from Crackers to Coffins"

 

[William Sommerwerck]

"Jeffrey Angus" <jangus@suddenlink.net> wrote in message
news:itq5iu$2ha$1@dont-email.me...

On 6/21/2011 7:25 AM, William Sommerwerck wrote:
"Jeffrey Angus"<jangus@suddenlink.net> wrote in message
news:itp42h$858$1@dont-email.me...
On 6/20/2011 10:36 PM, William Sommerwerck wrote:

Why don't you stop by, and I'll pull out the heating element part way.
Then you can touch one of the wires feeding the element with one hand,
and the a ground (such as the oven cabinet) with your other other
hand.

Care to bet your life on it?

I'd be happy to, idiot. I have enough sense to disconnect it first.

Oh. I thought all that was needed was to disconnect one side.

Uh huh, you're purposely talking in circles here....

You only have to disconnect one side to make the heater not heat.
You have to disconnect BOTH sides to make sure it's doesn't have
power on it to safely service the unit.

Of course. That's why I wondered why you were saying what you did -- since
the whole point of my original plaint was that only one side was disconected
from the line.

My toaster oven doesn't shut off when you open the door, either because
B&D
was cheap, or the designer didn't think anything bad would ever happen.
Older models did, including ones with sealed heating elements.

Does your gas oven shut it self off when you open the door?

Good question. I've never owned a gas oven, so I don't know. However, a gas
oven offers only the possibility of burning one's self -- not electrocution.
And for a number of obvious reasons, you wouldn't want to shut it off that
way, anyway.

What kind of red herring is this? It's a fucking toaster oven, not
a front loading washing machine.

It's not a red herring. It's that toaster ovens /used/ to be designed to
fully shut off the power when the door was opened, even though the chance of
users electrocuting themselves was less than minuscule. I don't see why this
shouldn't apply to ovens.

 

[whit3rd]

On Sunday, June 19, 2011 8:10:09 AM UTC-7, William Sommerwerck wrote:

The Calrod(tm) heating elements are nichrome wires sealed in a metal tube
full of magnesium oxide. The probability of the wire shorting to the metal
tube is extremely small. But if the user lifted the hinged bottom element to
clean under it (which is not "service" in the manual's sense -- you are not
told to shut off the power), s/he would be grabbing a live element, with
possibly fatal results.

In my electric oven, the oven elements ARE calrod-type, and
grabbing one you'd be touching only the grounded metal
sheath. Presumably, the electric element in question is bare
nichrome wire, thus a shock hazard if not disconnected from
both legs of the 220V?

 

[Sylvia Else]

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:

On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.

 

[Michael A. Terrell]

Sylvia Else wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

That's what the 2 pole fuse/circuit breaker is for.

Sylvia.

--
It's easy to think outside the box, when you have a cutting torch.

 

On Thu, 23 Jun 2011 12:27:06 +1000, Sylvia Else
<sylvia@not.here.invalid> wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.
I had exactly this happen over a decade ago. The center resistance

element started arcing to the outer sheath. This action was clearly
visible. When turning off the oven didn't help, I did what any
intelligent person should do - I turned off the circuit breaker.

I repeat - only a fool works on electrical equipment without making
sure it has been disconnected from power. 'Assuming' that both sides
of the power line are switched is stupid. Beleiving that the circuit
breaker is correctly labeled is foolish. Trusting the circuit breaker
is working correctly is only slightly less so.

About 5 years ago a lady named Gina Marie Wylie published an online
serial called 'Spitfire and Messerschmidt'. In the story, an Air
Conditioning serviceman is called upon to determine why the central
air conditioner has stopped. In exquisite detail it is described how
he checked the thermostat, then turned off the circuit breaker, pulled
the access panel, then used a voltmeter to verify the power was off.
When Davey (AKA Messerschmidt) questions this, the serviceman explains
"I have a six year old son. I look forward to going home and playing
with him tonight. I don't want someone to have to explain to him that
Daddy was in a hurry, made a mistake, and won't ever be coming home."

I'm sure the OP's significant other would not be comforted by the
epitath 'I thought it was turned off.'

PlainBill

 

[Dave Platt]

In article <cuf707dv7sminprbpnrh97du01gcqj9m1h@4ax.com>,
<PlainBill@yawhoo.com> wrote:

I'm sure the OP's significant other would not be comforted by the
epitath 'I thought it was turned off.'

Well said.

I understand that if you look at the statistics on people who suffer
injuries while working with (e.g.) power woodworking tools such as
table saws and lathes, you find:

- A significant but moderate percentage of "newbies" who didn't
read the instructions and warnings, and thus "didn't know better",

and

- A rather higher percentage of people with quite a lot of experience
with the equipment, who (when asked about it afterwards) say
something like "Yeah, I knew better, I knew I was taking a shortcut
and ignoring Precaution X".

As they say, "Familiarity breeds contempt" - in this case, familiarity
with the equipment or working environment tends to breed contempt for
safety precautions. "I got away with that before..."

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Sylvia Else]

On 24/06/2011 8:22 AM, Michael A. Terrell wrote:

Sylvia Else wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.


That's what the 2 pole fuse/circuit breaker is for.

It takes time to reach it, and that time may not be available.

Sylvia.

 

[Sylvia Else]

On 24/06/2011 8:53 AM, PlainBill@yawhoo.com wrote:

On Thu, 23 Jun 2011 12:27:06 +1000, Sylvia Else
sylvia@not.here.invalid> wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.
I had exactly this happen over a decade ago. The center resistance
element started arcing to the outer sheath. This action was clearly
visible. When turning off the oven didn't help, I did what any
intelligent person should do - I turned off the circuit breaker.

I'm not so convinced that people who aren't used to fiddling with the
breaker box would immediately think of that in the heat (?) of the
moment. IMHO the switch on an appliance should disconnect the power, at
least if the appliance and supply are correctly wired. If the appliance
uses live and neutral, then a single pole switch is sufficient, but if
it uses two live wires, it should have a double pole switch.

Leaving aside the fault that occurs while an appliance is in use, if
parts of the appliance are live when the appliance is turned off, then
it can still go up in flames if a fault develops within. This was not
such an infrequenty occurence in the UK when TVs weren't earthed and had
unpolarised power cords which could result in the chassis (!) being
live, even when the TV was turned off.

Sylvia.

 

[Michael A. Terrell]

Sylvia Else wrote:

On 24/06/2011 8:22 AM, Michael A. Terrell wrote:

Sylvia Else wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.


That's what the 2 pole fuse/circuit breaker is for.

It takes time to reach it, and that time may not be available.

The element is inside a metal oven. How long do you think it will
take for the defctive element to burn a hole in it? How long before the
breaker would trip or the fuse would open on their own?


--
It's easy to think outside the box, when you have a cutting torch.

 

[Sylvia Else]

On 24/06/2011 7:20 PM, Michael A. Terrell wrote:

Sylvia Else wrote:

On 24/06/2011 8:22 AM, Michael A. Terrell wrote:

Sylvia Else wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.


That's what the 2 pole fuse/circuit breaker is for.

It takes time to reach it, and that time may not be available.


The element is inside a metal oven. How long do you think it will
take for the defctive element to burn a hole in it? How long before the
breaker would trip or the fuse would open on their own?

How long was the problem festering before the user noticed?

If it doesn't matter how long it takes for the user to reach the circuit
breaker, then it doesn't matter if they don't bother.

An ELT would trip straight away, if one's fitted, which it might not be
in this kind of circuit. There's no guarantee that there'd ever be an
overcurrent trip.

Sylvia.

 

[Michael A. Terrell]

Sylvia Else wrote:

Michael A. Terrell wrote:

Sylvia Else wrote:

Michael A. Terrell wrote:

The element is inside a metal oven. How long do you think it will
take for the defctive element to burn a hole in it? How long before the
breaker would trip or the fuse would open on their own?

How long was the problem festering before the user noticed?

Festering? Get real. We aren't talking low temperature an a few mA.

If it doesn't matter how long it takes for the user to reach the circuit
breaker, then it doesn't matter if they don't bother.

An ELT would trip straight away, if one's fitted, which it might not be
in this kind of circuit. There's no guarantee that there'd ever be an
overcurrent trip.

Emergency Locator Transmitter?
Extremely Large Telescope?

These are the only uses of 'ELT' I've seen in the United States. It
is where I live, and so does the OP.


Sigh. Think it through. The body of the oven is grounded. If a
calrod element is failing, it isn't gradual. If it shorts to the metal
body the fuse blows, or the breaker trips since it is less than a full
load resistance.

If the element opens inside the metal tube, it generally creates
plasma which burns through the casing and opens the element
permanently. Even a bad connector will self destruct at those currents.
There is an exceedingly small chance for an intermittent element.


--
It's easy to think outside the box, when you have a cutting torch.

 

[Arfa Daily]

"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:96i69vFe9hU1@mid.individual.net...

On 24/06/2011 8:53 AM, PlainBill@yawhoo.com wrote:
On Thu, 23 Jun 2011 12:27:06 +1000, Sylvia Else
sylvia@not.here.invalid> wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both
"phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get
higher
voltages by spanning them. (I assume each voltage is referenced to
some
"neutral" point.) In my preceding apartment, I took advantage of this
to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.
I had exactly this happen over a decade ago. The center resistance
element started arcing to the outer sheath. This action was clearly
visible. When turning off the oven didn't help, I did what any
intelligent person should do - I turned off the circuit breaker.


I'm not so convinced that people who aren't used to fiddling with the
breaker box would immediately think of that in the heat (?) of the moment.
IMHO the switch on an appliance should disconnect the power, at least if
the appliance and supply are correctly wired. If the appliance uses live
and neutral, then a single pole switch is sufficient, but if it uses two
live wires, it should have a double pole switch.

Leaving aside the fault that occurs while an appliance is in use, if parts
of the appliance are live when the appliance is turned off, then it can
still go up in flames if a fault develops within. This was not such an
infrequenty occurence in the UK when TVs weren't earthed and had
unpolarised power cords which could result in the chassis (!) being live,
even when the TV was turned off.

Sylvia.

In all the years that I was directly involved with with TV sets in the UK,
working for one of the big four rental companies, I can only ever remember
one TV "going up in flames". It most certainly was not a common or frequent
occurrence. Further, I don't think I can recall any commonly sold make or
model, which ever employed an earth connection to the chassis. As for power
cords not being polarised, it depends exactly what you mean by that. In the
very early days, there were some sets that used a two pin plug-in power lead
which could be reversed. Likewise, there were two pin power sockets which
again could have the plugs for them reversed. However, by the time TV was
firmly established in the UK as an 'in every home' item, these sets were
long gone, and fixed power leads with colour-polarised wires, were the norm.
When we went over to the 13 A three pin wall socket convention, then as long
as the plug had been wired correctly, a 'live chassis' TV could never
actually have its chassis connected to the 'live' side of the incoming line
power. As to the chassis being live " even when the TV was turned off ", the
vast majority of sets that I saw employed a two pole power switch, ganged to
the volume control, so when they were switched off, both the line and the
neutral wires were disconnected from the TV.

On the cooker isolation issue, here in the UK, electric cookers are
typically connected via a permanently wired power cord that goes to a custom
outlet plate specifically designed and sold for the purpose. It is usual for
that outlet plate to be well down the wall behind the cooker, but connected
inside the wall to a further 'panel' mounted above counter height. On this
panel is either a large red switch on its own, or a large red switch, and a
three pin conventional power outlet. This is the double pole isolation
switch for the cooker, and is in addition to the fuse and breaker covering
this (independent) circuit, back at the fuse board.

http://www.pvrdirect.co.uk/productinfo.aspx?catref=SMJW45CUC

Arfa

 

On Fri, 24 Jun 2011 11:07:08 +1000, Sylvia Else
<sylvia@not.here.invalid> wrote:

On 24/06/2011 8:53 AM, PlainBill@yawhoo.com wrote:
On Thu, 23 Jun 2011 12:27:06 +1000, Sylvia Else
sylvia@not.here.invalid> wrote:

On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.


Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.
I had exactly this happen over a decade ago. The center resistance
element started arcing to the outer sheath. This action was clearly
visible. When turning off the oven didn't help, I did what any
intelligent person should do - I turned off the circuit breaker.


I'm not so convinced that people who aren't used to fiddling with the
breaker box would immediately think of that in the heat (?) of the
moment. IMHO the switch on an appliance should disconnect the power, at
least if the appliance and supply are correctly wired. If the appliance
uses live and neutral, then a single pole switch is sufficient, but if
it uses two live wires, it should have a double pole switch.

Leaving aside the fault that occurs while an appliance is in use, if
parts of the appliance are live when the appliance is turned off, then
it can still go up in flames if a fault develops within. This was not
such an infrequenty occurence in the UK when TVs weren't earthed and had
unpolarised power cords which could result in the chassis (!) being
live, even when the TV was turned off.

Sylvia.

Let's take a look at what will happen if the heating element fails by
shorting from the resistance element to the sheath. I will assume
that the failure I observed is worst case - an actual arc formed.
This gradually (1-2" per minute) moved toward the end of the heating
element. As the length of the resistance element got shorter, the
current would rise. Eventually the circuit breaker would trip. The
chance of a fire was very small. Most modern kitchen ranges have self
cleaning ovens which clean by heating themselves up high enough the
grease and spills are oxidized.

As I stated before, the problem was not in the design. Granted,
William Sommerwerk would not have received a shock if both lines were
interuurpted. However, that's not absolute protection. Switch and
relay contacts do weld together, triacs do short. One particular
brand of circuit breaker has been banned because the contacts tend to
weld together.

The chain of events is simple - The range was designed to meet certain
standards. William Sommerwerk assumed it was designed to his
standards. What is more, he was so confident in his assumption, he
failed to take the most emementary precaution of actually testing that
the terminal was not live.

Perhaps some may feel I am paranoid, but I have observed enough cases
where things were not as they should have been that I don't trust
labels, nor do I trust circuit breakers. Heck, I don't even trust a
simple neon bulb tester unless I check it!!

I've seen licensed electricians swap live and neutral wires in an
outlet box. I've seen a breaker box where the position labeled
'range' actually held two 15 amp breakers. I've seen a 12 gauge
(rated for 20 Amps) wire hooked to a 45 amp circuit breaker. I've
seen 'TN' wires (for installation in a conduit) strung across an attic
to power a ceiling fan in the room below.

PlainBill

 

[Wild_Bill]

Circuit breakers don't need to be explained.

In probably less than 1/1000 of installations in any relatively modern home,
there is a power plug (on a short cord) and receptacle for a kitchen range..
it's a service disconnect.

Disconnects are defined and required by codes in many places, certainly by
the NEC, and just plain (un?)-common sense.

--
Cheers,
WB
..............


"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:itjhi0$sjn$1@dont-email.me...

I just had to replace the bottom element in my GE oven, and discovered --
to
my great surprise -- that one side of the element is always "hot" -- that
is, it has voltage on it. I will be calling Appliance Park next week and
verbally tearing someone a new oven cavity.

Is this normal? And if it is, is it for some reason other than saving
money?

--
"We already know the answers -- we just haven't asked the right
questions." -- Edwin Land

 

[klem kedidelhopper]

On Jun 23, 6:53 pm, PlainB...@yawhoo.com wrote:

On Thu, 23 Jun 2011 12:27:06 +1000, Sylvia Else



syl...@not.here.invalid> wrote:
On 21/06/2011 12:11 PM, Jeffrey Angus wrote:
On 6/20/2011 7:16 PM, William Sommerwerck wrote:
Remember, it ONLY takes ONE switch to OPEN a series circuit.
That is ALL that is required to control whether or not the
element gets hot or cools off.

You were not paying attention! Any heating device that uses both "phases"
requres TWO switches to open it.

Oh, and by the way, since you brought it up, the bit about
both of the 240 volt sources being "hot with respect to
neutral". The heating elements are connected ACROSS the 240
VAC source, NOT split with each half going from the two
sources to neutral. (That would require a double contact to
turn each PAIR of heating elements on and off.)

I'm not sure what you're talking about. First, there is no "240V"
source in
my condo. There are multiple 120V sources from which you can get higher
voltages by spanning them. (I assume each voltage is referenced to some
"neutral" point.) In my preceding apartment, I took advantage of this to
build a break-out box -- all to code, I have several electrician
friends who
advised me -- to provide individual lines for my class A power amps.

As someone else kindly pointed out, this oven has one side of its
elements
hard-wired to AC. Bad, bad, bad, bad idea.

Damn you are fucking dense William.

The heating element from one hot lead to the other hot lead.
At NO time is there a connection to Neutral. Hence it ONLY
requires a SINGLE pole switch to open a SERIES circuit.

I see no inconsistency. A correctly functioning heating element can be
turned off, in the sense of no longer heating, by means of a single pole
switch.

But what about a non-correctly functioning heating element? One, for
example, that's shorted to its grounded covering somewhere along its
length. This could result in part of the element overheating, and an
owner noticing this would likely respond by turning the appliance off at
its switch. In the case of a heating element that spans two 110 v lines
in opposite phase, turning it off by a single pole switch won't have the
desired effect. Better hope that an earth leakage detector is fitted in
the supply lines, and works.

Sylvia.

I had exactly this happen over a decade ago.  The center resistance
element started arcing to the outer sheath.  This action was clearly
visible.  When turning off the oven didn't help, I did what any
intelligent person should do - I turned off the circuit breaker.

I repeat - only a fool works on electrical equipment without making
sure it has been disconnected from power.  'Assuming' that both sides
of the power line are switched is stupid. Beleiving that the circuit
breaker is correctly labeled is foolish. Trusting the circuit breaker
is working correctly is only slightly less so.

About 5 years ago a lady named Gina Marie Wylie published an online
serial called 'Spitfire and Messerschmidt'.  In the story, an Air
Conditioning serviceman is called upon to determine why the central
air conditioner has stopped.  In exquisite detail it is described how
he checked the thermostat, then turned off the circuit breaker, pulled
the access panel, then used a voltmeter to verify the power was off.
When Davey (AKA Messerschmidt) questions this, the serviceman explains
"I have a six year old son.  I look forward to going home and playing
with him tonight.  I don't want someone to have to explain to him that
Daddy was in a hurry, made a mistake, and won't ever be coming home."

  I'm sure the OP's significant other would not be comforted by the
epitath 'I thought it was turned off.'

PlainBill

That was one of the best things said so far. I heard about a utility
worker who walked into 1100VAC at a sub station some years ago. He too
thought that "the power was off". He spent the rest of his short life
on life support. We shouldn't need to be given a reason to be safe but
just in case someone does, just read 'Spitfire and Messerschmidt'.

You know William it seems that we like to buy the same appliances. I
also had a Black and Decker toaster oven some years ago and I too
remember that both sides of the line were switched off when you opened
the door. (I burnished and bent those contacts many times until they
just eventually "evaporated" and we had to throw the damn toaster
out). But after thinking about it, what puzzles me now is why did they
bother to switch both a 120V hot as well as a neutral? I still think
that it's prudent to disconnect power before working on something,
(whenever you can that is), but it seems to make no sense to
disconnect a neutral on a 120V circuit considering they can't be
bothered to disconnect both sides of the line on a 240V appliance.
Lenny
Lenny