OT -- switching heating elements

[William Sommerwerck]

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

 

[Sylvia Else]

On 19/06/2011 10:57 AM, William Sommerwerck 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 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]

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 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]

On 6/18/2011 9:51 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.

Are you stupid? NOTHING gets worked on while connected to power.

Jeff


--
"Everything from Crackers to Coffins"

 

[William Sommerwerck]

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.

"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]

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.

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?

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.

Jeff


--
"Everything from Crackers to Coffins"

 

[Sylvia Else]

On 19/06/2011 1:20 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.

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.

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.

 

[hrhofmann@att.net]

On Jun 18, 7:57 pm, "William Sommerwerck" <grizzledgee...@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?

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

So, the thermostat just opens one side of the 230V line?

 

[William Sommerwerck]

"Jeffrey Angus" <jangus@suddenlink.net> wrote in message
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]

"Sylvia Else" <sylvia@not.here.invalid> wrote in message
news:9659ggFle2U1@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]

On Sun, 19 Jun 2011 03:40:55 -0700, "William Sommerwerck"
<grizzledgeezer@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]

Did AP sell you the part?

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

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

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

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

 

[William Sommerwerck]

From: "Rich Webb" <bbew.ar@mapson.nozirev.ten>

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]

"nesesu" <neil_sutcliffe@telus.net> wrote in message
news:4f1a18f6-e12a-42b6-a55f-87f3c19ef5b2@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" <grizzledgeezer@comcast.net> wrote in message
news:itkitt$h2$1@dont-email.me...

"Jeffrey Angus" <jangus@suddenlink.net> wrote in message
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.)


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]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:zXoLp.2426$Zv3.76@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.

 

[nesesu]

On Jun 18, 8:42 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 19/06/2011 1:20 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.

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.

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.

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]

Let's let this drop.

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.

 

[William Sommerwerck]

"klem kedidelhopper" <captainvideo462009@gmail.com> wrote in message
news:57d4ccef-84f8-42ef-a4be-10becef02288@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]

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.

Also applies to guns... Always assume the weapon is loaded.