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* OT -- switching heating elements - 6 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/2359de19aee3537a?hl=en
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* Introduction to Econometrics, 3/E Stock Watson Solution manual and test Bank
is available for purchase at affordable prices. Contact me at estudyguides[at]
gmail.com to buy it today. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/f92a491b569d225f?hl=en
* Guitar Pickups Coil Ringing Test Electric Testing PUP - 2 messages, 2
authors
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==============================================================================
TOPIC: OT -- switching heating elements
http://groups.google.com/group/sci.electronics.repair/t/2359de19aee3537a?hl=en
==============================================================================

== 1 of 6 ==
Date: Wed, Jun 22 2011 7:27 pm
From: 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.

== 2 of 6 ==
Date: Thurs, Jun 23 2011 3:22 pm
From: "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.

== 3 of 6 ==
Date: Thurs, Jun 23 2011 3:53 pm
From: PlainBill@yawhoo.com

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

== 4 of 6 ==
Date: Thurs, Jun 23 2011 4:37 pm
From: dplatt@radagast.org (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!

== 5 of 6 ==
Date: Thurs, Jun 23 2011 5:57 pm
From: 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.

== 6 of 6 ==
Date: Thurs, Jun 23 2011 6:07 pm
From: 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.

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== 1 of 1 ==
Date: Thurs, Jun 23 2011 9:41 am
From: anusiya begam

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== 1 of 1 ==
Date: Thurs, Jun 23 2011 9:40 am
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TOPIC: Introduction to Econometrics, 3/E Stock Watson Solution manual and test
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estudyguides[at]gmail.com to buy it today.
http://groups.google.com/group/sci.electronics.repair/t/f92a491b569d225f?hl=en
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== 1 of 1 ==
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TOPIC: Guitar Pickups Coil Ringing Test Electric Testing PUP
http://groups.google.com/group/sci.electronics.repair/t/3f84b39bfef04db0?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Jun 23 2011 9:03 pm
From: "Wild_Bill"

So, I've disassembled another Epiphone humbucker pickup of the same basic
type/series (but instead the neck pickup), and the Ringer Test results are
the same (4 rings whether assembled or disassembled).

Assembled pickup DC resistance 10.8k ohm, inductance 4.7H.

Disassembled pickup, coils separated from magnet, frame plate.. individual
coils inductance 2.3H

Bare coils, no screws or core plugs.. 830mH each.

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

"Wild_Bill" <wb_wildbill@XSPAMyahoo.com> wrote in message
news:XbmLp.51997$BZ.33265@en-nntp-03.dc1.easynews.com...
>I know there are at least a few participants here who have guitars, so I
>was wondering if anyone here has attemped a Ringer Test (inductor Q) on
>guitar pickups.
>

== 2 of 2 ==
Date: Thurs, Jun 23 2011 9:57 pm
From: "Phil Allison"

"Wild_Bill"
> So, I've disassembled another Epiphone humbucker pickup of the same basic
> type/series (but instead the neck pickup), and the Ringer Test results are
> the same (4 rings whether assembled or disassembled).
>
> Assembled pickup DC resistance 10.8k ohm, inductance 4.7H.
>
> Disassembled pickup, coils separated from magnet, frame plate.. individual
> coils inductance 2.3H
>
> Bare coils, no screws or core plugs.. 830mH each.

** The number is visible cycles of ringing is a guide to the Q of a resonant
circuit - the Q is approximately equal to the number of cycles.

So, your pickup coil has about a Q of 4 - either bare or assembled.

Why?

The frequency of ringing is much higher when bare.

Q = the ratio of impedance to resistance at a given frequency.

.... Phil

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