OT -- switching heating elements
William Sommerwerck
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
hrho...@att.net
wrote:
So, the thermostat just opens one side of the 230V line?
Sylvia Else
> 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 something you surmised by looking at the wiring, or just a
result of a meter measurement? In the latter case, it could be that the
alleged qualified electrician who installed the appliance has connected
it the wrong way wroung.
Sylvia.
William Sommerwerck
the breaker -- on the assumption that no engineer in his right mind would
leave one side of the heating element powered.
As I pulled out the element, I got a big (though not fat) spark. I was more
surprised than frightened.
You're correct. It appears the thermostat switches only one side of the
heating element.
By the way, the replacement was ordered Thursday morning and arrived
Saturday morning at 9:30. Not too shabby. (Or should I say shabbes?) It took
only a few minutes to replace the element, and the oven works fine.
Jeffrey Angus
> I should have explained that I went to remove the element without opening
> the breaker -- on the assumption that no engineer in his right mind would
> leave one side of the heating element powered.
Are you stupid? NOTHING gets worked on while connected to power.
Jeff
--
"Everything from Crackers to Coffins"
William Sommerwerck
>> opening the breaker -- on the assumption that no engineer in his
>> right mind would leave one side of the heating element powered.
> Are you stupid? NOTHING gets worked on while connected to power.
"Foolish" might be more apt than "stupid". And people commonly work on
powered TVs and other electronic equipment -- with proper precautions, of
course.
We still need an answer to the original question... Why?
Jeffrey Angus
Um, stupid is the correct term William.
"Bench testing live equipment" is NOT the same as working on
an oven connected to a 240 circuit.
As to why it only opens one side of the circuit, that's simple,
it only requires one switch to open a series circuit. It takes
two to remove power. Hence the coupled dual pole breakers on
the source (breaker) panel.
Sylvia Else
I think it's perfectly normal for appliances to switch only one pole of
the power supply, that pole being the live one. Same with power points
and light switches. I don't think I've seen an appliance with a double
power power switch.
What's not normal, and dangerous, is for the neutral wire to be the one
switched. Either the oven is miswired internally, is miswired to the
mains supply, or the mains supply is miswired. Whichever it is needs to
be fixed.
Sylvia.
William Sommerwerck
news:itjqdb$9f2$1...@dont-email.me...
> On 6/18/2011 10:20 PM, William Sommerwerck wrote:
>>>> I should have explained that I went to remove the element without
>>>> opening the breaker -- on the assumption that no engineer in his
>>>> right mind would leave one side of the heating element powered.
> As to why it only opens one side of the circuit, that's simple,
> it only requires one switch to open a series circuit. It takes
> two to remove power. Hence the coupled dual-pole breakers
> on the source (breaker) panel.
Jeffrey, that's a tautological answer. I'm looking for an engineering and/or
safety justification for not providing a dual-pole switch within the oven.
(The economic "justification" is obvious.)
William Sommerwerck
news:9659gg...@mid.individual.net...
> On 19/06/2011 1:20 PM, William Sommerwerck wrote:
>> We still need an answer to the original question... Why?
> I think it's perfectly normal for appliances to switch only one pole
> of the power supply, that pole being the live one. Same with power
> points and light switches. I don't think I've seen an appliance with
> a double power power switch.
I have have. I've owned two of the classic GE/B&D toaster ovens, and they
switched both sides of the line when you opened the door. This is a good
safety precaution. My current B&D toaster oven does not remove the power
when the door is opened.
With respect to this particular oven, something "live" was NOT being
switched. How do you explain the spark, otherwise? The 208V or 240V are
(presumably) taken from across two phases (or whatever you want to call
them -- we needn't rehash that argument), one of which is not switched. The
oven's "metalwork" is grounded/"neutraled" so that a short from the
heating-element circuit to the metal will trip the breaker -- which it did.
> What's not normal, and dangerous, is for the neutral wire to be the
> one switched. Either the oven is miswired internally, is miswired to
> the mains supply, or the mains supply is miswired. Whichever it is
> needs to be fixed.
If I understand multi-phase wiring, the 240V is taken from across two
phases. Connecting or disconnecting the neutral would have no effect on that
voltage.
In single-phase systems, it would, of course, be foolish to switch just the
neutral. This would leave the hot "hot", and open the possibility of
electrocution from hot to ground, such as a plumbing fixture.
Yet again, an example of how a simple question becomes a tsimmes.
Rich Webb
<grizzle...@comcast.net> wrote:
>If I understand multi-phase wiring, the 240V is taken from across two
>phases. Connecting or disconnecting the neutral would have no effect on that
>voltage.
>
>In single-phase systems, it would, of course, be foolish to switch just the
>neutral. This would leave the hot "hot", and open the possibility of
>electrocution from hot to ground, such as a plumbing fixture.
>
>
>Yet again, an example of how a simple question becomes a tsimmes.
Residential wiring is, AIUI, typically "anti-phase" rather than multiple
(usually three) phase. One phase of the 3-phase distribution from the
substation is dropped with a center-tapped service transformer. The
center is earthed (at one point) and that becomes the neutral for the
120 volt services. 240 volt service doesn't have a neutral; both sides
are "hot" with respect to earth ground, so in the situation described
you'd expect to see 120 V to ground on the heater element.
Presumably, what you're seeing meets UL requirements. Perhaps (just
speculating here) the intent is that the oven should have an on-off
switch that does isolate both sources, and a thermostatic switch that
cycles on only one?
Also: tsimmes; I learned a new word! ;-)
--
Rich Webb Norfolk, VA
Wild_Bill
Have you RTFM?
Would you prefer that the part not be available?
Will you be working on other appliances without removing the power?
Is what normal?
--
Cheers,
WB
.............
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:itjhi0$sjn$1...@dont-email.me...
nesesu
We are talking at cross purposes here. In the UK and Australia, the
240V has one side neutral and the other 'hot' while in North America
the 240V is both sides hot and centre neutral. In my stove the oven
thermostat is the typical single pole switch in one side of the
element circuit, but both sides pass through the 'oven function'
selector switch that offers 'OFF', 'Bake', 'Broil' and 'Clean'. When
that switch is OFF then the element is dsconnected from both hot
feeds.
In Canada, a heating thermostat for controlling 240V space heaters
[permanently connected] may be a single pole type, but if it has an
'OFF' position marked, it MUST open both circuits.
Neil S.
William Sommerwerck
> Residential wiring is, AIUI, typically "anti-phase" rather than multiple
> (usually three) phase. One phase of the 3-phase distribution from the
> substation is dropped with a center-tapped service transformer. The
> center is earthed (at one point) and that becomes the neutral for the
> 120 volt services. 240 volt service doesn't have a neutral; both sides
> are "hot" with respect to earth ground, so in the situation described
> you'd expect to see 120 V to ground on the heater element.
That was my general assumption.
> Presumably, what you're seeing meets UL requirements. Perhaps
> (just speculating here) the intent is that the oven should have an on-off
> switch that does isolate both sources, and a thermostatic switch that
> cycles on only one?
I'm not sure whether UL requirements have any direct connection with
/consumer/ safety. * The UL evaluation is more "generic" -- is this device
likely to catch on fire, or start a fire? Is it inherently unsafe to use?
etc, etc, etc
The user manual says the owner should not perform any service on the oven --
but if s/he does, the power should be first disconnected at the breaker.
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.
> Also: tsimmes; I learned a new word! ;-)
For those unfamiliar with it, it means "stew", in both the literal and
figurative senses.
* To clarify... On a segment of "I've Got a Secret" that involved a giant
boa constrictor, Steve Allen said "Would you believe it? This snake is
perfectly safe. <beat> You're in terrible danger, but the snake is safe!"
William Sommerwerck
news:4f1a18f6-e12a-42b6...@q14g2000prh.googlegroups.com...
> We are talking at cross purposes here. In the UK and Australia, the
> 240V has one side neutral and the other 'hot' while in North America
> the 240V is both sides hot and centre neutral. In my stove the oven
> thermostat is the typical single pole switch in one side of the
> element circuit, but both sides pass through the 'oven function'
> selector switch that offers 'OFF', 'Bake', 'Broil' and 'Clean'. When
> that switch is OFF then the element is dsconnected from both hot
> feeds.
I hadn't thought of the selector switch. Good point.
Needless to day, the oven switch was in the Off position.
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:itkitt$h2$1...@dont-email.me...
So what other justification do you think you are looking for ? It works.
It's perfectly safe until some fool works on it 'live' in the expectation
that he's going to be safe, and it saves money on the build cost of the
appliance. When the equipment is used 'closed up' in its normal operational
configuration, the manufacturer has no legitimate safety concerns beyond
that. Also, given the way American society sues at the drop of a hat, I'm
pretty sure that the manufacture will have his arse covered in that doing it
this way meets any and all safety regulations that might apply.
Sorry, but I can only echo Mr Angus's sentiments that working on such
equipment without fully isolating it first, is highly irresponsible,
especially for someone of your usually pedantic persuasion, who I'm sure
would normally be shouting "never assume anything !!" at anyone else who
posted a similar story here ...
Arfa
William Sommerwerck
news:zXoLp.2426$Zv3...@newsfe26.ams2...
>> (The economic "justification" is obvious.)
> So what other justification do you think you are looking for?
I guess I'm looking for a groveling "Gee-ee, we're stupid" apology from GE.
> It works. It's perfectly safe until some fool works on it 'live' in the
expectation
> that he's going to be safe, and it saves money on the build cost of the
> appliance.
As another poster pointed out, there are ovens with both sides switched at
the "bake" selector.
> Sorry, but I can only echo Mr Angus's sentiments that working on such
> equipment without fully isolating it first, is highly irresponsible,
> especially for someone of your usually pedantic persuasion, who I'm sure
> would normally be shouting "never assume anything !!" at anyone else who
> posted a similar story here ...
Criticism accepted... But in this case I might very well have taken "anyone
else's" side.
William Sommerwerck
I got an extremely useful response -- one I didn't expect -- about some
ovens "properly" disconnecting the AC at the oven-mode selector. This gives
me something useful to discuss with GE.
Thank you all for your interest and help.
klem kedidelhopper
<grizzledgee...@comcast.net> wrote:
> "Arfa Daily" <arfa.da...@ntlworld.com> wrote in message
Interestingly I also own a GE stove and coincidentally my bake element
developed a hot spot one day and "exploded" open and also needed to be
replaced. I never even thought of the possibility that only one side
of the 240 was being switched off from the control unit when I
replaced it, Like you William I just would have expected such a design
to be both impractical as well as unsafe. However I did unplug the
stove first, but just purely from habit, ( and because I really don't
like working on live circuits, unless there is no other alternative).
So in all honesty I made the same assumption that you did with the
exception that my stove was unplugged.
The model number of my stove is JBP64 and it is almost ten years old.
GE was nice enough to provide a service page with their appliances,
(at least they were still doing it at the time we purchased this
model), and it included a schematic. I just looked at it and
incredible as it may seem, sure enough L2 is directly connected to one
side of both the bake and broil elements!
I've never forgotten the words of one of my teachers many years ago
when I was in electronics school. He never seemed to tire of reminding
us to "never assume that the power is off". And I try very hard not
to. Good advice when you run into something unexpected like this. Lenny
William Sommerwerck
news:57d4ccef-84f8-42ef...@n28g2000vbs.googlegroups.com...
> Interestingly I also own a GE stove and coincidentally my bake element
> developed a hot spot one day and "exploded" open.
Quite by chance, I saw it burning. I thought it was a bit of food. Near the
"socket"?
> The model number of my stove is JBP64 and it is almost ten years old.
Mine's from a (probably) related series, JBP26, and a year or two older.
> GE was nice enough to provide a service page with their appliances,
> (at least they were still doing it at the time we purchased this
> model), and it included a schematic. I just looked at it and
> incredible as it may seem, sure enough L2 is directly connected to one
> side of both the bake and broil elements!
> Thanks for the confirmation. I'm still going to call GE. You will be
quoted.
William Sommerwerck
> when I was in electronics school. He never seemed to tire of reminding
> us to "never assume that the power is off". And I try very hard not
> to. Good advice when you run into something unexpected like this.
Also applies to guns... Always assume the weapon is loaded.
Plai...@yawhoo.com
<grizzle...@comcast.net> wrote:
>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?
That is common. The resistance element is encapsulated in a
protective sheath. You cannot remove the heating element without
removing the back of the appliance. I would wager the appliance was
shipped with a warning label indicating it should be removed only by
qualified servicers.
Also, recall if either a mechanical or solid state double pole relay
were used, one side could fail (contacts welded or SCR shorted) and
you would never know the difference.
There are titles for those who work on appliances without first
ensuring it is disconnected. "The Dear Departed" is one. "Candidate
for a Darwin Award" is another. I prefer 'Fool".
PlainBill
William Sommerwerck
news:6tmsv6t6b0f46pn2u...@4ax.com...
>> 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?
> That is common. The resistance element is encapsulated in a
> protective sheath. You cannot remove the heating element without
> removing the back of the appliance. I would wager the appliance was
> shipped with a warning label indicating it should be removed only by
> qualified servicers.
You don't have to take off the back of the oven. You can remove the element
in situ. Just undo two 1/4" hex-head screws, pull out the base of the
element a bit, and pull off the friction-fit connectors.
klem kedidelhopper
wrote:
> <PlainB...@yawhoo.com> wrote in message
Well at least one side of the line is disconnected. Thank God for
small favors. So when you reach inside the oven and pull the hot
terminal off the element while you're leaning on the open door with
your chest, you only pass 120 through you heart....... Lenny
William Sommerwerck
>> You don't have to take off the back of the oven. You can remove the
>> element in situ. Just undo two 1/4" hex-head screws, pull out the base
>> of the element a bit, and pull off the friction-fit connectors.
> Well at least one side of the line is disconnected.
If both sides were connected, the element would be on! Wouldn't it?
> Thank God for small favors. So when you reach inside the oven
> and pull the hot terminal off the element while you're leaning on
> the open door with your chest, you only pass 120 through you heart.
Well, I was clothed. And the door was off.
Ron D.
is responsible for switching both.
I've only seen one piece of industrial equipment that had a breaker
in the neutral. Basically 3 huge HIGH POWER like 15 kW*3 picture
tube like power supplies BUT VERY HIGH POWER. 15 kV at 3 amps.
The system required 70 Amp 3 phase 208 VAC to operate. Blink and your
dead. Keys are required to get passed the access doors on the
equipment.
William Sommerwerck
news:934e1a22-dd8b-414f...@a10g2000vbz.googlegroups.com...
> Triac controlled heaters would only switch one side. The disconnect
> is responsible for switching both.
> I've only seen one piece of industrial equipment that had a breaker
> in the neutral. Basically 3 huge HIGH POWER like 15 kW*3 picture
> tube like power supplies BUT VERY HIGH POWER. 15 kV at 3 amps.
> The system required 70 Amp 3 phase 208 VAC to operate. Blink and
> you're dead. Keys are required to get passed the access doors on the
> equipment.
For those who enjoy calling me an idiot... I used to service klystrons with
20kV anode supplies. One was vehwy, vehwy kehful around these. You not only
made sure the power was off, but you used a conductive pole to short the
supply.
Sylvia Else
It's true that I had overlooked the strange :P approach to supplying
domestic power in North America.
One possibility that the OP needs to address is that the switch is
simply broken, or has one pole bridged by a wire.
But either way, I hold with the consensus here - you don't start taking
appliances apart while any part of them is powered, which includes their
switches. (But pleads guilty to removing and installing boards on PCs
while they're on standby!).
Sylvia.
spamtrap1888
wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
>
> news:c57a5c52-9fa3-44b0...@dq9g2000vbb.googlegroups.com...
>
> >> You don't have to take off the back of the oven. You can remove the
> >> element in situ. Just undo two 1/4" hex-head screws, pull out the base
> >> of the element a bit, and pull off the friction-fit connectors.
> > Well at least one side of the line is disconnected.
>
> If both sides were connected, the element would be on! Wouldn't it?
>
But you wouldn't be replacing the element if it was on, right?
William Sommerwerck
news:46d71b8a-ea16-41d8...@22g2000prx.googlegroups.com...
On Jun 19, 5:14 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
> news:c57a5c52-9fa3-44b0...@dq9g2000vbb.googlegroups.com...
>>>> You don't have to take off the back of the oven. You can remove the
>>>> element in situ. Just undo two 1/4" hex-head screws, pull out the base
>>>> of the element a bit, and pull off the friction-fit connectors.
>>> Well, at least one side of the line is disconnected.
>> If both sides were connected, the element would be on! Wouldn't it?
> But you wouldn't be replacing the element if it was on, right?
Correct. But you said "Well, at least one side of the line is disconnected".
klem kedidelhopper
wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
Someone is saving a buck. There must be money involved somehow. It's
the least common denominator. It always is.
Lenny
William Sommerwerck
> Someone is saving a buck. There must be money involved somehow.
> It's the least common denominator. It always is.
As someone said... "Don't assume conspiracies when simple stupidity is
enough to explain something."
Jeffrey Angus
It's a series circuit, it only take ONE switch to open it.
There is absolutely NO reason to use a dual pole switch.
I'm tired of hearing "It's the evil corporations" being at fault
for people that can't or won't pay attention when doing their
own repairs and try to shift the blame from their own carelessness.
Jeff
--
"Everything from Crackers to Coffins"
Smitty Two
"William Sommerwerck" <grizzle...@comcast.net> wrote:
>
> As someone said... "Don't assume conspiracies when simple stupidity is
> enough to explain something."
I thought you were going to drop this thread, but since your words and
actions don't match, I'll agree with others who've opined that you're
the stupid one here, working on a 240 volt system with it plugged in.
William Sommerwerck
> On 6/20/2011 8:10 AM, William Sommerwerck wrote:
> > "klem kedidelhopper"<captainvi...@gmail.com> wrote in message
> >
news:87dc74d5-a347-4fc4...@a31g2000vbt.googlegroups.com...
>>> Someone is saving a buck. There must be money involved somehow.
>>> It's the least common denominator. It always is.
>> As someone said... "Don't assume conspiracies when simple stupidity is
>> enough to explain something."
> It's a series circuit, it only take ONE switch to open it.
> There is absolutely NO reason to use a dual pole switch.
I'm sorry, but you're wrong -- probably because you aren't familiar with
American wiring.
The standard line voltage in North America is 120V (or thereabouts). Most
houses are wired to two "phases" (or whatever the correct term is). When
higher voltage is needed -- for a dryer, range, or water heater -- the
device is connected across these phases, producing a net voltage of around
210V.
Now, if you connect /either/ of these phases to the neutral, current will
flow. This is what happened when I moved the element -- it banged into the
neutral (the oven wall itself, presumably), and tripped the breaker.
As someone else pointed out, my range and other GE ranges have one side of
the baking and broiling elements permanently connected to one of the phases,
making them /live/ as long as the breaker is connected. There is no reason
for this, other than saving a dollar or two manufacturing costs.
> I'm tired of hearing "It's the evil corporations" being at fault
> for people that can't or won't pay attention when doing their
> own repairs and try to shift the blame from their own carelessness.
I spoke with a customer-service rep at GE this morning, who agreed that
switching only one side of the line was potentially (pun intended?)
dangerous. Think of an oven in a flooded basement.
William Sommerwerck
news:prestwhich-8F379...@news.eternal-september.org...
I was, but people kept responding.
Jeffrey Angus
> "Jeffrey Angus"<jan...@suddenlink.net> wrote in message
>
>> There is absolutely NO reason to use a dual pole switch.
>
> I'm sorry, but you're wrong -- probably because you aren't familiar with
> American wiring.
>
> The standard line voltage in North America is 120V (or thereabouts). Most
> houses are wired to two "phases" (or whatever the correct term is). When
> higher voltage is needed -- for a dryer, range, or water heater -- the
> device is connected across these phases, producing a net voltage of around
> 210V.
>
> Now, if you connect /either/ of these phases to the neutral, current will
> flow. This is what happened when I moved the element -- it banged into the
> neutral (the oven wall itself, presumably), and tripped the breaker.
>
> As someone else pointed out, my range and other GE ranges have one side of
> the baking and broiling elements permanently connected to one of the phases,
> making them /live/ as long as the breaker is connected. There is no reason
> for this, other than saving a dollar or two manufacturing costs.
And in short (pun intended) you were using it wrong.
Under normal operation there is absolutely no reason what so ever
for one or the other side to go to neutral.
>> I'm tired of hearing "It's the evil corporations" being at fault
>> for people that can't or won't pay attention when doing their
>> own repairs and try to shift the blame from their own carelessness.
>
> I spoke with a customer-service rep at GE this morning, who agreed that
> switching only one side of the line was potentially (pun intended?)
> dangerous. Think of an oven in a flooded basement.
The cabinet is supposed to be grounded.
This isn't like the classic "All the wiring is floating" toaster in the
bath tub trick.
And if you're foolish enough to try using an electrical oven (or any
other electrical appliance) in a flooded basement, you deserve anything
that happens to you.
Jeffrey Angus
it makes a couple of interesting statements.
1. Make sure you appliance is properly installed and GROUNDED.
2. Before performing any service, disconnect the range power
supply at the household distribution panel by removing the
fuse or switching off the circuit breaker.
But what I find really interesting...
"Do not attempt to repair or replace any part of your range
unless is specifically recommended in the manual. All other
servicing should be referred to a qualified technician."
The user manual goes on to tell you how to clean it, and how
to change the light bulb in the oven. NOWHERE does it tell you
to replace the burner elements.
So which part of the manual did you think did not apply to
you?
Well, William, wanna give it another go at how you're the
victim here of a corporation's greed?
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.
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.)
"Removing power" on the other hand is accomplished, per the
manual, by turning off the source. (And yes, that turns off
BOTH sides of the 240 VAC supply.)
William Sommerwerck
> The cabinet is supposed to be grounded. This isn't like the classic
> "All the wiring is floating" toaster in the bath tub trick.
I'm not sure about that. I think there is a similarity. "Mythbusters" showed
that someone /can/ be electrocuted when a heater or toaster is tossed into a
bathtub.
> And if you're foolish enough to try using an electrical oven (or any other
> electrical appliance) in a flooded basement, you deserve anything that
> happens to you.
Of course! But what would happen if someone waded into the flooded basement
to shut off the breakers (which is what I was thinking of)? If the water
were high enough to enter the oven cavity, the water would be "hot".
I agree that no one should enter a flooded room without wearing waterproof
rubber boots, but... Many possible accidents -- however unlikely -- are
/predictable/. Why not avoid them in the first place, especially when it
adds next to nothing to the cost of the appliance?
Many years ago, my father was using a metal-bodied electric drill in the
basement. He was wearing leather-soled shoes and standing on concrete, which
(as it is in many basements) was faintly damp. The drill's motor shorted out
to the metal body, and he was nearly electrocuted. This was before
double-insulated tools, and outside of not standing on a thick rubber mat, *
he was doing nothing wrong. At least, not by the standards of the day.
In the US, new construction requires GFI outlets near sinks or other water
supplies.
* Black rubber objects often contain carbon, which is more conductive than
you might think. I discovered this more than 30 years ago when trying to use
rubber washers to insulate rack-mount equipment.
William Sommerwerck
> By the way, on page 3 of the users manual for the GE JBP64
> it makes a couple of interesting statements.
> 1. Make sure you appliance is properly installed and GROUNDED.
> 2. Before performing any service, disconnect the range power
> supply at the household distribution panel by removing the
> fuse or switching off the circuit breaker.
> But what I find really interesting...
> "Do not attempt to repair or replace any part of your range
> unless is specifically recommended in the manual. All other
> servicing should be referred to a qualified technician."
I am an qualified technician -- despite what you might think.
> Well, William, wanna give it another go at how you're the
> victim here of a corporation's greed?
I'm not anybody's victim.
> 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.
Jeffrey Angus
>> 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.
William Sommerwerck
> 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
> 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.
William Sommerwerck
> 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
> "Jeffrey Angus"<jan...@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.
William Sommerwerck
> On 6/21/2011 7:25 AM, William Sommerwerck wrote:
> > "Jeffrey Angus"<jan...@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
> 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
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
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.
Plai...@yawhoo.com
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
<Plai...@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 <dpl...@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
It takes time to reach it, and that time may not be available.
Sylvia.
Sylvia Else
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
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?
Sylvia Else
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
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.
Arfa Daily
"Sylvia Else" <syl...@not.here.invalid> wrote in message
news:96i69v...@mid.individual.net...
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
Plai...@yawhoo.com
<syl...@not.here.invalid> wrote:
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
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" <grizzle...@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
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
William Sommerwerck
news:0ac7ac73-dfe4-4765...@em7g2000vbb.googlegroups.com...
> 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.
I can think of a number of reasons, the principal one being that it's easy
to stick a fork in a toaster, much harder to stick one in an oven. Of
course, this particular toaster used sealed elements, so it's unlikely
anything within the cavity would ever be electrically hot.
The other reason for switching the neutral is that there's no guarantee the
neutral is neutral -- some houses are miswired.
I had a great conversation the other day with a woman at GE's CEO
headquarters, who apparently does nothing but talk to Really Unhappy
customers. I admitted my carelessness, but she didn't put me down, and
listened seriously. She said she would report this to The Council. ("The
Kryptonian Council of Elders?" That got a big laugh out of her.) Apparently,
GE has a group that pays attention to engineering issues.
You might have heard that GE is bringing major-appliance manufacturing back
to Appliance Park. This is apparently due to rising wages in other
countries, and GE's figuring out how to build appliances more efficiently. A
guy at GE told me that the goal is return the manufacture of /all/ major
appliances.
klem kedidelhopper
<grizzledgee...@comcast.net> wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
So then why not assume that there are enough idiots out there like
people who use ground busters because they have older ungrounded
outlets in their homes or better yet those that file the larger prong
on a plug down so that it will fit in an older outlet. If you really
consider these possibilities then why not switch both the hot and
neutral on every 120V appliance. Lets make them all "idiot proof" and
then everyone will be safe. I mean should we assume that anyone is
going to have to take responsibility for their own actions any more?
When I was a kid, (back in the stone age). there was no such thing as
a Calrod element, well maybe there might have been but I remember that
most appliances like toasters, ovens, broilers, even space heaters
were made with exposed nichrome wire. Many toasters still are. I
worked on them all from the time I was a teenager. Most people, even
the non technical ones realized after they had stuck a fork in the
toaster once to not do that again. I'm sure that they still do. But
really lets answer the bigger question. What is the goal here? Is it
to build an appliance as cheaply, I'm sorry, (cost effectively), as
possible or is it to keep people, even the stupid ones safe? And
getting back to my other question: why did B& D obviously think that
it was a good idea 15 years ago to switch both the hot and neutral on
my toaster oven but now they don't?
You just can't convince me that the least common denominator isn't
money. Yeah maybe I am a little paranoid too, but it doesn't mean
they're not out to get me.....Lenny
William Sommerwerck
> When I was a kid, (back in the stone age). there was no such thing as
> a Calrod element, well maybe there might have been but I remember that
> most appliances like toasters, ovens, broilers, even space heaters
> were made with exposed nichrome wire.
The GE Calrod unit goes back at least to the 50s, and probably the 30s. An
electric oven using exposed nichrome wires would not be a very good idea.
> Many toasters still are. I
> worked on them all from the time I was a teenager. Most people, even
> the non technical ones realized after they had stuck a fork in the
> toaster once to not do that again. I'm sure that they still do. But
> really lets answer the bigger question. What is the goal here? Is it
> to build an appliance as cheaply, I'm sorry, (cost effectively), as
> possible or is it to keep people, even the stupid ones safe? And
> getting back to my other question: why did B& D obviously think that
> it was a good idea 15 years ago to switch both the hot and neutral on
> my toaster oven but now they don't?
If there is an answer, it's that you do certain things simply because they
make sense, regardless of what you think a user might or might not do.
klem kedidelhopper
wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
I have my mother's old broiler/rotisserie from the 50's down in the
basement. My wife asked me to get rid of it so many times but I just
can't seem to part with it. (I remember the roasts and rotisserie
chickens we used to have when I was a kid). It has a coiled nichcrome
wire element as they all did at that time. Early Lionel trains were
connected directly to the AC line through a carbon pile or rheostat.
Things were a lot different in "the old days". I finally just hid it.
Maybe I'll get it out one day and cook a roast for her. Lenny
klem kedidelhopper
wrote:
> "klem kedidelhopper" <captainvideo462...@gmail.com> wrote in message
I had another question as long as we're talking about ovens. When you
use the self cleaning function on these stoves, I believe that both
elements are turned on for an extended period of time. We usually hold
off doing this until a cold spell hits as lot of heat is generated and
warms the kitchen nicely. Essentially everything in the oven is
incinerated down to a fine gray powder. If you think of the bake and
broil elements as "filaments" of a sort, with a finite life span,
doesn't invoking this function shorten their life? Lenny
Jeffrey Angus
> I had another question as long as we're talking about ovens. When you
> use the self cleaning function on these stoves, I believe that both
> elements are turned on for an extended period of time. We usually hold
> off doing this until a cold spell hits as lot of heat is generated and
> warms the kitchen nicely. Essentially everything in the oven is
> incinerated down to a fine gray powder. If you think of the bake and
> broil elements as "filaments" of a sort, with a finite life span,
> doesn't invoking this function shorten their life? Lenny
One would think so, if one were inclined to think all corporations are
evil and all design engineers are stupid.
The misconception here is that the "normal" heating range on those
elements is the design center. It is NOT. The "clean" cycle is the
design center.
William Sommerwerck
> On 6/26/2011 10:44 PM, klem kedidelhopper wrote:
>> I had another question as long as we're talking about ovens. When
>> you use the self cleaning function on these stoves, I believe that both
>> elements are turned on for an extended period of time. We usually
>> hold off doing this until a cold spell hits as lot of heat is generated
>> and warms the kitchen nicely. Essentially everything in the oven is
>> incinerated down to a fine gray powder. If you think of the bake and
>> broil elements as "filaments" of a sort, with a finite life span,
>> doesn't invoking this function shorten their life?
If it does, then one has to weigh the convenience of self-cleaning against
the inconvenience and higher cost of manual cleaning.
> One would think so, if one were inclined to think all corporations are
> evil and all design engineers are stupid.
> The misconception here is that the "normal" heating range on those
> elements is the design center. It is NOT. The "clean" cycle is the
> design center.
I've never used the self-cleaning feature on my oven. Yet the bottom element
burned through after only about 10 years of use. Another member of this
group reported the same thing for their GE.
I had a conservative, slightly paranoid friend (hi, Greg -- miss ya bad) who
claimed materials science was sufficiently advanced that auto manufacturers
were able to control how long a car engine lasted. I pooh-poohed this, but
he was probably correct. Few products are made to last "as long as
possible", because it tends to increase the price.
Jeffrey Angus
> I had a conservative, slightly paranoid friend (hi, Greg -- miss ya bad) who
> claimed materials science was sufficiently advanced that auto manufacturers
> were able to control how long a car engine lasted. I pooh-poohed this, but
> he was probably correct. Few products are made to last "as long as
> possible", because it tends to increase the price.
It's NOT some evil conspiracy.
The CONSUMER has been screaming for the past 30 years,
"I don't care if it's crap, I want it now, I want it
cheap and I don't care if it only last 6 months because
I'll be bored with it by then anyway."
Manufacturers are supplying them with what they asked for.
Jeff Liebermann
Not exactly. In the not so distant past, manufacturers produced
products, set prices as best they could, and retailers did their best
to sell at that price point. No more. With the demise of the small
retailers, the large warehouse stores are doing it backwards. They
set a price at which they know they can sell and make a profit, and
then demand that their suppliers deliver at that price. If the
supplier complains, then another supplier will be found. Walmart is
famous for doing that. The result is that manufacturers have
cheapened their products, reduced the quality, cut corners, deleted
options, etc. Anything to meet the price target. If there are any
subsequent quality problems, it's cheaper to deal with warranty
returns, than to design in the necessary quality that prevent returns.
I see something quite different than customers that get bored in 6
months. I get complaints that it only lasts 6 months and that they
want quality at any price. I deliver quite a few overkill computer
systems, where a lesser machine would have been more than adequate. I
see hybrid auto sales doing quite well, mostly on the basis of quality
and alleged economy, where both would be difficult to innumerate and
financially justify. The GUM (great unwashed masses) may have been
demanding cheap junk for 30 years, but now seem to have begun to tire
of the junk.
As for controlling product lifetime, it's been here for quite a while.
Semiconductor life can be predicted based on the number of thermal
cycles. Electrolytic capacitor life can be predicted by a combination
of temperature and operating conditions. Battery lifetimes are well
known and controllable. High power LED's have a predictable lifetime.
I've seen products (i.e. old Sony TV's and monitors) that seem to have
had components selected for a specific target lifetime. Modeling
programs make such designs fairly easy.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Geoffrey S. Mendelson
> They
> set a price at which they know they can sell and make a profit, and
> then demand that their suppliers deliver at that price. If the
> supplier complains, then another supplier will be found. Walmart is
> famous for doing that. The result is that manufacturers have
> cheapened their products, reduced the quality, cut corners, deleted
> options, etc. Anything to meet the price target. If there are any
> subsequent quality problems, it's cheaper to deal with warranty
> returns, than to design in the necessary quality that prevent returns.
It's a lot older than you think. Around 1980 or so, Sears wanted to sell a
black and white portable TV and they could not get anyone in the US or Japan
to sell them one.
They shopped around and found Samsung, which was a large company in Korea,
but unheard of outside who was willing to do it. That's when the large
international Korean electronics giants were born.
As for quality programs, it's not the build quality that matters as much
as you think. It's the testing. Intel started it (although they may probably
were not the first) when they produced RAM chips for the IBM PC and other
small computers.
The only made only produced one chip speed and if the chips failed, they were
tested at a slower speed, if they failed that they were tested until they
failed at the slowest speed sold, or passed one of the tests.
They actually had to do it, their first chips were so bad that ECC (error
correcting code) processing had to be built into the hardware of the first
computer made using them. It was done at the XEROX PARC, you can read about
it in "Dealers in Lightening".
Now they don't bother to test anything at the manufacturing plant, the
consumer tests it for them. :-(
Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.
William Sommerwerck
news:o9ni07tdgtqi38t7p...@4ax.com...
> In the not so distant past, manufacturers produced
> products, set prices as best they could, and retailers did their best
> to sell at that price point. No more. With the demise of the small
> retailers, the large warehouse stores are doing it backwards. They
> set a price at which they know they can sell and make a profit, and
> then demand that their suppliers deliver at that price. If the
> supplier complains, then another supplier will be found. Walmart is
> famous for doing that.
Wal*mart also (supposedly) insists that suppliers reduce their prices every
year.
I know of no other "big box" store that does these things.
I've been in Wal*mart a few times, and I didn't see where their prices were
categorically lower than other stores'. Regardless, I don't buy from
Wal*mart.
I'm old enough to remember when discounting was uncommon. Luskin's ("Jack
and Joe will save you dough.") of Baltimore was one of the first stores in
the US to discount appliances, electronics, etc. It's now taken for granted
that you don't pay "list price" for anything -- assuming that "list price"
has any meaning.
> The result is that manufacturers have
> cheapened their products, reduced the quality, cut corners, deleted
> options, etc. Anything to meet the price target. If there are any
> subsequent quality problems, it's cheaper to deal with warranty
> returns, than to design in the necessary quality that prevent returns.
In the case of Wal*mart, the story goes that companies are sometimes forced
to send production overseas.
> I see something quite different than customers that get bored in 6
> months. I get complaints that it only lasts 6 months and that they
> want quality at any price. I deliver quite a few overkill computer
> systems, where a lesser machine would have been more than adequate. I
> see hybrid auto sales doing quite well, mostly on the basis of quality
> and alleged economy, where both would be difficult to innumerate and
> financially justify. The GUM (great unwashed masses) may have been
> demanding cheap junk for 30 years, but now seem to have begun to tire
> of the junk.
Again, I'm not sure. If that were so, there wouldn't be any $30 DVD players
at Fry's.
Cheap merchandise -- of whatever quality -- is part of the "vicious circle"
of rapid technological change and obsolesence.
Smitty Two
Jeff Liebermann <je...@cruzio.com> wrote:
> As for controlling product lifetime, it's been here for quite a while.
> Semiconductor life can be predicted based on the number of thermal
> cycles. Electrolytic capacitor life can be predicted by a combination
> of temperature and operating conditions. Battery lifetimes are well
> known and controllable. High power LED's have a predictable lifetime.
> I've seen products (i.e. old Sony TV's and monitors) that seem to have
> had components selected for a specific target lifetime. Modeling
> programs make such designs fairly easy.
Henry Ford ("Ford: The Men and the Machine" is an outstanding book, but
don't waste your time with the movie) sent roving teams of engineers out
to the junkyards of America to dismantle junked Fords and see which
parts were still good. One thing they couldn't find was a worn-out
kingpin, so Ford started making them lighter and cheaper. No sense
having a kingpin outlive the car. That was close to 100 years ago.
William Sommerwerck
news:prestwhich-44CFE...@news.eternal-september.org...
Which strikes me as perverse -- why not improve the quality of those parts
that were worn out? Oh, wait... cars would last longer, and there would be
fewer sales, over time.
Jeff Liebermann
<g...@mendelson.com> wrote:
>Now they don't bother to test anything at the manufacturing plant, the
>consumer tests it for them. :-(
Quite true. Modern robotic manufacturing methods have the advantage
of producing fairly uniform output. The 1.5% AQL QA test is somewhat
of a thing of the past, as it's only necessary to test a tiny number
of sample units, to predict the performance of the rest.
From my experience, in the distant past, 100% parametric (partial)
testing of the product along the production line gives better results.
This is where key parts of the PCB are indirectly tested during board
assembly, but before final assembly. Tests such as total current
drain, end to end gain, board weight, and visual (camera) inspection,
do not provide a complete test, but give a fair indication if the PCB
is going to work. The idea is to eliminate final test, which such
methods do fairly well. The assumption is that a collection of small
tests during assembly, do better than a final test. To the casual
observer, it may look bad that there's no final test, but along the
board assembly line, there's plenty of testing being done.
Incidentally, some robotic parts stuffers test the components as they
are inserted in the PCB.
Jeff Liebermann
<grizzle...@comcast.net> wrote:
>Wal*mart also (supposedly) insists that suppliers reduce their prices every
>year.
Walmart offers the suppliers increased sales volume in trade for a
decreased profit margin. That will work only if the supplier has an
efficiency improvement program in place. It will also only work with
suppliers that are large enough to have sufficient credit available to
fund such programs. That eliminates all but the largest suppliers.
The dilemma for Walmart is that there are really only a few vendors
qualified to sell to Walmart under such a program. There's also
little to stop them from illegally organizing and fixing prices. When
this happens, Walmart finds a medium size supplier, and offers to back
their growth into a large supplier, in trade for profit margin
concessions. How it works in Mexico:
<http://econ.la.psu.edu/~jtybout/SDS%20and%20NAFTA_NBER.pdf>
The US gets cheap Mexican products, while Mexico gets Walmart.
>I know of no other "big box" store that does these things.
My father sold lingerie to Sears during the 1960's thru mid 1980's.
Sears wasn't as obnoxious and as demanding as Walmart, but such
pricing policies (and others) were well established. However, Sears
had a different goal. They were not after the best price. They were
into growth. What they did was build up the business of their
suppliers, knowing that the supplier would need to obtain expensive
financing, and then abruptly cut off all orders. They could then buy
what was left of their supplier for peanuts.
>In the case of Wal*mart, the story goes that companies are sometimes forced
>to send production overseas.
Most domestic companies would prefer to use domestic production
facilities. It can be done, but not at the price points set by
Walmart. Similarly, if the competition wants to sell anywhere near
the same price point, they too have to go offshore, even if they don't
sell to Walmart.
>Cheap merchandise -- of whatever quality -- is part of the "vicious circle"
>of rapid technological change and obsolesence.
Good, fast, cheap.... pick two. The buying public has chosen fast and
cheap, so the quality will suffer. Where problems start is when
quality is unobtainable at any price. That's where I think we're
going.
Jeff Liebermann
<grizzle...@comcast.net> wrote:
>Wal*mart also (supposedly) insists that suppliers reduce their prices every
>year.
It's not just Walmart. Here's Apple demanding what appears to be
regular price cuts on iPad components:
Report: Apple Demands 10 Percent Price Cuts from iPad
Parts Suppliers
<http://www.pcmag.com/article2/0,2817,2387397,00.asp>
William Sommerwerck
>> Cheap merchandise -- of whatever quality -- is part of the
>> "vicious circle" of rapid technological change and obsolesence.
> Good, fast, cheap.... pick two. The buying public has chosen fast
> and cheap, so the quality will suffer. Where problems start is when
> quality is unobtainable at any price. That's where I think we're going.
Regardless of whether this is true or false, it's definitely has hurt Sony,
which depended on its premium products to create a favorable image for
everything it sold.
Sony used to be a true innovator that make a lot of Neat Stuff, but those
days seem gone. Glad I got a 7M3 AIBO while they were still available.
Cydrome Leader
> On 6/21/2011 7:25 AM, William Sommerwerck wrote:
>> "Jeffrey Angus"<jan...@suddenlink.net> wrote in message
>>> 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?
Ha!
KR
wrote:
> "Sylvia Else" <syl...@not.here.invalid> wrote in message
>
>
> > On 19/06/2011 1:20 PM, William Sommerwerck wrote:
> >> We still need an answer to the original question... Why?
> > I think it's perfectly normal for appliances to switch only one pole
> > of the power supply, that pole being the live one. Same with power
> > points and light switches. I don't think I've seen an appliance with
> > a double power power switch.
>
> I have have. I've owned two of the classic GE/B&D toaster ovens, and they
> switched both sides of the line when you opened the door. This is a good
> safety precaution. My current B&D toaster oven does not remove the power
> when the door is opened.
>
> With respect to this particular oven, something "live" was NOT being
> switched. How do you explain the spark, otherwise? The 208V or 240V are
> (presumably) taken from across two phases (or whatever you want to call
> them -- we needn't rehash that argument), one of which is not switched. The
> oven's "metalwork" is grounded/"neutraled" so that a short from the
> heating-element circuit to the metal will trip the breaker -- which it did.
>
> > What's not normal, and dangerous, is for the neutral wire to be the
> > one switched. Either the oven is miswired internally, is miswired to
> > the mains supply, or the mains supply is miswired. Whichever it is
> > needs to be fixed.
>
> If I understand multi-phase wiring, the 240V is taken from across two
> phases. Connecting or disconnecting the neutral would have no effect on that
> voltage.
>
> In single-phase systems, it would, of course, be foolish to switch just the
> neutral. This would leave the hot "hot", and open the possibility of
> electrocution from hot to ground, such as a plumbing fixture.
Believe it or not, I have seen in the past, appliances where the
neutral was switched
I was told that this was a tactic to allow a lower rated switch to be
used.
Same with old Ferguson fluorescent ballasts in common use in the
`1960-70s
The diagram on them showed them wired into the neutral supply with the
live coming
through the tube. Probably again to lower rate the thing ?
>
> Yet again, an example of how a simple question becomes a tsimmes.
KR
> On 19/06/2011 1:20 PM, William Sommerwerck wrote:
>
> >>> opening the breaker -- on the assumption that no engineer in his
> >>> right mind would leave one side of the heating element powered.
>
> >> Are you stupid? NOTHING gets worked on while connected to power.
>
> > "Foolish" might be more apt than "stupid". And people commonly work on
> > powered TVs and other electronic equipment -- with proper precautions, of
> > course.
>
> > We still need an answer to the original question... Why?
>
> I think it's perfectly normal for appliances to switch only one pole of
> the power supply, that pole being the live one. Same with power points
> and light switches. I don't think I've seen an appliance with a double
> power power switch.
>
> switched. Either the oven is miswired internally, is miswired to the
> mains supply, or the mains supply is miswired. Whichever it is needs to
> be fixed.
>
I think you will find that this is in the USA, They have 2 x 120v 180
out of phase, and
if you go across the 2 actives you get 240v. This is used on
appliances like this and
air cons that suck a lot of power, in order to reduce the currents
involved.
It would be like 3 phase here, but we have 3 actives and 120
separation. Same rule,
ALL 3 phases must be turned off or the appliance is still "live"