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Today's topics:

* OT -- switching heating elements - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/2359de19aee3537a?hl=en
* hai good morning - 2 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/fa01de5cec09c209?hl=en

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TOPIC: OT -- switching heating elements
http://groups.google.com/group/sci.electronics.repair/t/2359de19aee3537a?hl=en
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== 1 of 3 ==
Date: Tues, Jun 21 2011 9:11 am
From: "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.

== 2 of 3 ==
Date: Wed, Jun 22 2011 10:30 am
From: 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?

== 3 of 3 ==
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.

==============================================================================
TOPIC: hai good morning
http://groups.google.com/group/sci.electronics.repair/t/fa01de5cec09c209?hl=en
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== 1 of 2 ==
Date: Wed, Jun 22 2011 6:58 pm
From: sakthivel vel

: http://123maza.com/35/city149/

== 2 of 2 ==
Date: Wed, Jun 22 2011 7:09 pm
From: sakthivel vel

: http://123maza.com/35/city149/

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