This Whirlpool electric stove, model number RF0100, appears to be an older
model. If you were wondering what blasted the ground lead of my Kill-A-Watt
meter which I posted about two days ago in the thread about the Phillips
security screw, this is the culprit. The schematic is he
http://members.dslextreme.com/users/...tric-stove.jpg as
I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or at least
not yet. I was trying to at least get it to work on 120V because only the
oven will be used and at very low heat, probably around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been disconnected because
they are not needed. This particular model does not have a light or a clock
as shown in the schematic. I wired it so that L1 went to hot (black), L2
went to N (white), and N to ground (green). The load across the electric
plug, hot to neutral, with the oven switch on, is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes no sense
to me. I've tried two different dvm's and they both give bizarre results.
When starting at the 2M ohm range, the meter starts at about 700k and counts
down to about 300k and holds there. When I move the switch over to the 20M
ohm range, the meter starts at about 2.3M ohm and counts up. The other meter
which is a portable meter counts backward too and then the minus sign
appears on the meter as if current is coming into the meter. From what I can
see, there aren't any capacitors or semiconductors interfering. The oven
thermostat has a thermocouple wired to it which for some reason is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either the oven
element switch, the broil element switch, or both. Then there is the
thermocouple wire which is wrapped(?) internally around the rotating control
that selects the oven temperature. I don't usually open oven thermostats so
I'm not sure what exactly is going on inside because once you open the
thermostat,
there is a spring inside the device which displaces everything. In any case,
at room
temperature, there is a connection from L1 to the bake and broil terminals
so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first plugged the
oven into my Sencore PR57 isolation transformer. The transformer can only
supply about 300 watts but I was more interested in measuring leakage
current. No surprise when the low side leakage to the metal frame measured
full deflection even with the power off to the oven. Not exactly the best
situation. The high side leakage was zero. I turned up the voltage slowly
and the current seemed to rise proportionately to the 17 ohm load until I
stopped at about 300 watts. I should mention that the heating element did
not seem to get warm. Also, the heating element impedance matched the load
across the power plug so that seemed like a good sign.

Then I plugged it directly into the wall outlet via the Kill-A-Watt meter. I
turned on the oven switch and an instant trip of the circuit breaker at the
sub panel occurred. So where is all this extra current coming from to cook
the ground plug on my Kill-A-Watt and trip the breaker? I must be missing
something very obvious.

Thanks for your reply.
--
David Farber
Los Osos, CA

On Wed, 20 Oct 2010 20:37:21 -0700, David Farber wrote:

I used to have the stove hooked up to a 240 volt circuit as indicated in the
schematic and it worked ok. But, now I don't have a 240V line.

Since you have admitted to dedicating that line to your marijuana
plant grow, why not STFU about it?
--
****! I thought no one knew, goddammit!
http://preview.tinyurl.com/29p4ody
Me, jacking off! http://preview.tinyurl.com/3xpntge Available For
Lessons!

I'm not really sure which heating element is still connected. Most of the
elements' wattages are listed on the wiring diagram, but the two on the left
side (bake, broil) of the diagram aren't (that I could see).
It could be, that the wattage of the element being used exceeds the total
wattage of the circuit breaker.
I would check to see if there are any other loads applied to the same AC
supply circuit.

Those temperature control symbols may represent the type that have internal
heated bi-metal type switches in them (dunno what they're called in the
trade, but commonly used in cooking appliances with heating elements).
In some Corning laboratory type hot plates that I have, these types of
switches make a fairly distinct sound.. a sort-of "tink" when the when the
switch's internal heated bi-metal strip opens the switch.
I believe a cam closes the switch contacts, then the heated bi-metal strip
opens the switch (a calculated/designed time delay, I guess).

The small bi-metal heater wire (inside the switch(s) will naturally have a
DC resistance. I wouldn't think that internal heater wire resistance would
change from just a DMM test lead voltage, but maybe they do. If I could get
to those lab hot plates, I'd do some checking instead of just speculating.

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


"David Farber" wrote in message
...
This Whirlpool electric stove, model number RF0100, appears to be an older
model. If you were wondering what blasted the ground lead of my
Kill-A-Watt
meter which I posted about two days ago in the thread about the Phillips
security screw, this is the culprit. The schematic is he
http://members.dslextreme.com/users/...tric-stove.jpg
as
I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as indicated in
the
schematic and it worked ok. But, now I don't have a 240V line. Or at least
not yet. I was trying to at least get it to work on 120V because only the
oven will be used and at very low heat, probably around 200 degrees to
cook
some ceramics. The stovetop and broiler wires have been disconnected
because
they are not needed. This particular model does not have a light or a
clock
as shown in the schematic. I wired it so that L1 went to hot (black), L2
went to N (white), and N to ground (green). The load across the electric
plug, hot to neutral, with the oven switch on, is 17 ohms. That makes
sense
to me. However the impedance reading from neutral to ground makes no sense
to me. I've tried two different dvm's and they both give bizarre results.
When starting at the 2M ohm range, the meter starts at about 700k and
counts
down to about 300k and holds there. When I move the switch over to the 20M
ohm range, the meter starts at about 2.3M ohm and counts up. The other
meter
which is a portable meter counts backward too and then the minus sign
appears on the meter as if current is coming into the meter. From what I
can
see, there aren't any capacitors or semiconductors interfering. The oven
thermostat has a thermocouple wired to it which for some reason is not
shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either the oven
element switch, the broil element switch, or both. Then there is the
thermocouple wire which is wrapped(?) internally around the rotating
control
that selects the oven temperature. I don't usually open oven thermostats
so
I'm not sure what exactly is going on inside because once you open the
thermostat,
there is a spring inside the device which displaces everything. In any
case, at room
temperature, there is a connection from L1 to the bake and broil terminals
so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first plugged the
oven into my Sencore PR57 isolation transformer. The transformer can only
supply about 300 watts but I was more interested in measuring leakage
current. No surprise when the low side leakage to the metal frame measured
full deflection even with the power off to the oven. Not exactly the best
situation. The high side leakage was zero. I turned up the voltage slowly
and the current seemed to rise proportionately to the 17 ohm load until I
stopped at about 300 watts. I should mention that the heating element did
not seem to get warm. Also, the heating element impedance matched the load
across the power plug so that seemed like a good sign.

Then I plugged it directly into the wall outlet via the Kill-A-Watt meter.
I
turned on the oven switch and an instant trip of the circuit breaker at
the
sub panel occurred. So where is all this extra current coming from to cook
the ground plug on my Kill-A-Watt and trip the breaker? I must be missing
something very obvious.

Thanks for your reply.
--
David Farber
Los Osos, CA

"David Farber" wrote in message
...

This Whirlpool electric stove, model number RF0100, appears to be an
older model. If you were wondering what blasted the ground lead of my
Kill-A-Watt
meter which I posted about two days ago in the thread about the
Phillips security screw, this is the culprit. The schematic is he
http://members.dslextreme.com/users/...tric-stove.jpg
as
I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as
indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or at
least not yet. I was trying to at least get it to work on 120V
because only the oven will be used and at very low heat, probably
around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been disconnected
because
they are not needed. This particular model does not have a light or a
clock
as shown in the schematic. I wired it so that L1 went to hot
(black), L2 went to N (white), and N to ground (green). The load
across the electric plug, hot to neutral, with the oven switch on,
is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes no
sense to me. I've tried two different dvm's and they both give
bizarre results. When starting at the 2M ohm range, the meter starts
at about 700k and counts
down to about 300k and holds there. When I move the switch over to
the 20M ohm range, the meter starts at about 2.3M ohm and counts up.
The other meter
which is a portable meter counts backward too and then the minus sign
appears on the meter as if current is coming into the meter. From
what I can
see, there aren't any capacitors or semiconductors interfering. The
oven thermostat has a thermocouple wired to it which for some reason
is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either
the oven element switch, the broil element switch, or both. Then
there is the thermocouple wire which is wrapped(?) internally around
the rotating control
that selects the oven temperature. I don't usually open oven
thermostats so
I'm not sure what exactly is going on inside because once you open
the thermostat,
there is a spring inside the device which displaces everything. In
any case, at room
temperature, there is a connection from L1 to the bake and broil
terminals so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first
plugged the oven into my Sencore PR57 isolation transformer. The
transformer can only supply about 300 watts but I was more
interested in measuring leakage current. No surprise when the low
side leakage to the metal frame measured full deflection even with
the power off to the oven. Not exactly the best situation. The high
side leakage was zero. I turned up the voltage slowly and the
current seemed to rise proportionately to the 17 ohm load until I
stopped at about 300 watts. I should mention that the heating
element did not seem to get warm. Also, the heating element
impedance matched the load across the power plug so that seemed like
a good sign. Then I plugged it directly into the wall outlet via the
Kill-A-Watt
meter. I
turned on the oven switch and an instant trip of the circuit breaker
at the
sub panel occurred. So where is all this extra current coming from
to cook the ground plug on my Kill-A-Watt and trip the breaker? I
must be missing something very obvious.

Thanks for your reply.
--
David Farber
Los Osos, CA

Wild_Bill wrote:
I'm not really sure which heating element is still connected. Most of
the elements' wattages are listed on the wiring diagram, but the two
on the left side (bake, broil) of the diagram aren't (that I could
see). It could be, that the wattage of the element being used exceeds the
total wattage of the circuit breaker.
I would check to see if there are any other loads applied to the same
AC supply circuit.

Those temperature control symbols may represent the type that have
internal heated bi-metal type switches in them (dunno what they're
called in the trade, but commonly used in cooking appliances with
heating elements). In some Corning laboratory type hot plates that I have,
these types of
switches make a fairly distinct sound.. a sort-of "tink" when the
when the switch's internal heated bi-metal strip opens the switch.
I believe a cam closes the switch contacts, then the heated bi-metal
strip opens the switch (a calculated/designed time delay, I guess).

The small bi-metal heater wire (inside the switch(s) will naturally
have a DC resistance. I wouldn't think that internal heater wire
resistance would change from just a DMM test lead voltage, but maybe
they do. If I could get to those lab hot plates, I'd do some checking
instead of just speculating.

Hi WB,

There's an upper and a lower element in the stove section. The top one is
called the broil and bottom one is the bake. When you turn the stove knob
from off to on, both broil and bake elements get energized. I disconnected
the broil element because I will not be doing any broiling. So what's left
is the bake element at the bottom. That presents about a 17 ohm load which
translates into approximately 850 watts. If the supply voltage were 240V,
that would increase the power to 3,400 watts. I'm not even sure 850 watts
can raise the temperature to 200°F (assuming I can get it working) in a
reasonable amount of time. Regarding the circuit breaker, there was really
nothing else on that circuit at the time it tripped. Even so, why would the
ground terminal be the one to take the hit? There shouldn't be any current
flowing through there, right? The way the stove is wired now is that the
neutral wire of the stove is connected to where L2 was before so the circuit
path is from L1, through the oven switch, through the heating element,
through L2 which is now wired to neutral.

Thanks for your reply.
--
David Farber
Los Osos, CA

"David Farber" wrote in message
...
Regarding the circuit breaker, there was really
nothing else on that circuit at the time it tripped. Even so, why would
the ground terminal be the one to take the hit? There shouldn't be any
current flowing through there, right? The way the stove is wired now is
that the neutral wire of the stove is connected to where L2 was before so
the circuit path is from L1, through the oven switch, through the heating
element, through L2 which is now wired to neutral.

Thanks for your reply.

David,

Is the breaker a GFCI type? That would explain the tripping, as the way you
have the stove wired, there is a large potential between neutral and ground
(in terms of a GFCI).

Brenda Ann wrote:
"David Farber" wrote in message
...
Regarding the circuit breaker, there was really
nothing else on that circuit at the time it tripped. Even so, why
would the ground terminal be the one to take the hit? There
shouldn't be any current flowing through there, right? The way the
stove is wired now is that the neutral wire of the stove is
connected to where L2 was before so the circuit path is from L1,
through the oven switch, through the heating element, through L2
which is now wired to neutral. Thanks for your reply.

David,

Is the breaker a GFCI type? That would explain the tripping, as the
way you have the stove wired, there is a large potential between
neutral and ground (in terms of a GFCI).

Not a GFCI. The circuit breaker is 20 amps and located in the sub panel.

How do you account for the large potential between neutral and ground? Since
there is no oven light or clock, the neutral wire in the schematic doesn't
really connect to anything except the chassis ground. Though I do agree with
you that in order for that circuit to trip and burn out the ground pin,
there is some major current flowing. I'd just like to be able to follow it
from beginning to end.

Thanks for your reply.
--
David Farber
Los Osos, CA

There is a comment included in the text on the wiring diagram label, wrt a
bonding strap.

I think you already know, but the earth ground should only have a path to
the exposed metal cabinet parts, and all other parts need to be electrically
isolated from earth ground (the insulating quality of the isolation needs to
exceed the applied/working voltage, hi-pot being the normal convention).

I believe an 800W element will create a lot of heat inside an enclosure. I
have a 500W 120VAC heater intended to heat engine block oil pans in winter,
and in low light in open air, the deep red color of the element armor can be
seen (not nichrome or resistance wire).

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


"David Farber" wrote in message
...

"David Farber" wrote in message
...

This Whirlpool electric stove, model number RF0100, appears to be an
older model. If you were wondering what blasted the ground lead of my
Kill-A-Watt
meter which I posted about two days ago in the thread about the
Phillips security screw, this is the culprit. The schematic is he
http://members.dslextreme.com/users/...tric-stove.jpg
as
I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as
indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or at
least not yet. I was trying to at least get it to work on 120V
because only the oven will be used and at very low heat, probably
around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been disconnected
because
they are not needed. This particular model does not have a light or a
clock
as shown in the schematic. I wired it so that L1 went to hot
(black), L2 went to N (white), and N to ground (green). The load
across the electric plug, hot to neutral, with the oven switch on,
is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes no
sense to me. I've tried two different dvm's and they both give
bizarre results. When starting at the 2M ohm range, the meter starts
at about 700k and counts
down to about 300k and holds there. When I move the switch over to
the 20M ohm range, the meter starts at about 2.3M ohm and counts up.
The other meter
which is a portable meter counts backward too and then the minus sign
appears on the meter as if current is coming into the meter. From
what I can
see, there aren't any capacitors or semiconductors interfering. The
oven thermostat has a thermocouple wired to it which for some reason
is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either
the oven element switch, the broil element switch, or both. Then
there is the thermocouple wire which is wrapped(?) internally around
the rotating control
that selects the oven temperature. I don't usually open oven
thermostats so
I'm not sure what exactly is going on inside because once you open
the thermostat,
there is a spring inside the device which displaces everything. In
any case, at room
temperature, there is a connection from L1 to the bake and broil
terminals so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first
plugged the oven into my Sencore PR57 isolation transformer. The
transformer can only supply about 300 watts but I was more
interested in measuring leakage current. No surprise when the low
side leakage to the metal frame measured full deflection even with
the power off to the oven. Not exactly the best situation. The high
side leakage was zero. I turned up the voltage slowly and the
current seemed to rise proportionately to the 17 ohm load until I
stopped at about 300 watts. I should mention that the heating
element did not seem to get warm. Also, the heating element
impedance matched the load across the power plug so that seemed like
a good sign. Then I plugged it directly into the wall outlet via the
Kill-A-Watt
meter. I
turned on the oven switch and an instant trip of the circuit breaker
at the
sub panel occurred. So where is all this extra current coming from
to cook the ground plug on my Kill-A-Watt and trip the breaker? I
must be missing something very obvious.

Thanks for your reply.
--
--
David Farber
Los Osos, CA

"David Farber" wrote in message
...

This Whirlpool electric stove, model number RF0100, appears to be
an older model. If you were wondering what blasted the ground lead
of my Kill-A-Watt
meter which I posted about two days ago in the thread about the
Phillips security screw, this is the culprit. The schematic is
he
http://members.dslextreme.com/users/...tric-stove.jpg
as I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as
indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or
at least not yet. I was trying to at least get it to work on 120V
because only the oven will be used and at very low heat, probably
around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been
disconnected because
they are not needed. This particular model does not have a light
or a clock
as shown in the schematic. I wired it so that L1 went to hot
(black), L2 went to N (white), and N to ground (green). The load
across the electric plug, hot to neutral, with the oven switch on,
is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes
no sense to me. I've tried two different dvm's and they both give
bizarre results. When starting at the 2M ohm range, the meter
starts at about 700k and counts
down to about 300k and holds there. When I move the switch over to
the 20M ohm range, the meter starts at about 2.3M ohm and counts
up. The other meter
which is a portable meter counts backward too and then the minus
sign appears on the meter as if current is coming into the meter.
From what I can
see, there aren't any capacitors or semiconductors interfering. The
oven thermostat has a thermocouple wired to it which for some
reason is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either
the oven element switch, the broil element switch, or both. Then
there is the thermocouple wire which is wrapped(?) internally
around the rotating control
that selects the oven temperature. I don't usually open oven
thermostats so
I'm not sure what exactly is going on inside because once you open
the thermostat,
there is a spring inside the device which displaces everything. In
any case, at room
temperature, there is a connection from L1 to the bake and broil
terminals so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first
plugged the oven into my Sencore PR57 isolation transformer. The
transformer can only supply about 300 watts but I was more
interested in measuring leakage current. No surprise when the low
side leakage to the metal frame measured full deflection even with
the power off to the oven. Not exactly the best situation. The high
side leakage was zero. I turned up the voltage slowly and the
current seemed to rise proportionately to the 17 ohm load until I
stopped at about 300 watts. I should mention that the heating
element did not seem to get warm. Also, the heating element
impedance matched the load across the power plug so that seemed
like a good sign. Then I plugged it directly into the wall outlet
via the Kill-A-Watt
meter. I
turned on the oven switch and an instant trip of the circuit
breaker at the
sub panel occurred. So where is all this extra current coming from
to cook the ground plug on my Kill-A-Watt and trip the breaker? I
must be missing something very obvious.

Thanks for your reply.
--
--
David Farber
Los Osos, CA

Wild_Bill wrote:
There is a comment included in the text on the wiring diagram label,
wrt a bonding strap.

I think you already know, but the earth ground should only have a
path to the exposed metal cabinet parts, and all other parts need to
be electrically isolated from earth ground (the insulating quality of
the isolation needs to exceed the applied/working voltage, hi-pot
being the normal convention).
I believe an 800W element will create a lot of heat inside an
enclosure. I have a 500W 120VAC heater intended to heat engine block
oil pans in winter, and in low light in open air, the deep red color
of the element armor can be seen (not nichrome or resistance wire).



Here's the way I see it. Starting from L1, current flows through the limit
switch then to the thermostat. If the thermostat switch is turned on by the
thermocouple, then the current continues on to the bake element and then the
circuit is completed when it connects to L2, which is where the neutral line
is. I don't see any connection to that and the metal cabinet parts. So
either my analysis is wrong or there is current leaking to ground.

Just so there is no confusion, from left to right in the schematic, the
original 240V wiring of L1, N, L2 has been changed to 120V wiring of, Line,
Ground, and N. I can remove the bonding strap which connects the chassis to
N in the 240V schematic or Ground in the 120V version that I came up with.
I'd just like to understand what's going on here.

Thanks for your reply.
--
David Farber
Los Osos, CA

David Farber wrote:
"David Farber" wrote in message
...

This Whirlpool electric stove, model number RF0100, appears to be
an older model. If you were wondering what blasted the ground lead
of my Kill-A-Watt
meter which I posted about two days ago in the thread about the
Phillips security screw, this is the culprit. The schematic is
he
http://members.dslextreme.com/users/...tric-stove.jpg
as I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as
indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or
at least not yet. I was trying to at least get it to work on 120V
because only the oven will be used and at very low heat, probably
around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been
disconnected because
they are not needed. This particular model does not have a light
or a clock
as shown in the schematic. I wired it so that L1 went to hot
(black), L2 went to N (white), and N to ground (green). The load
across the electric plug, hot to neutral, with the oven switch on,
is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes
no sense to me. I've tried two different dvm's and they both give
bizarre results. When starting at the 2M ohm range, the meter
starts at about 700k and counts
down to about 300k and holds there. When I move the switch over to
the 20M ohm range, the meter starts at about 2.3M ohm and counts
up. The other meter
which is a portable meter counts backward too and then the minus
sign appears on the meter as if current is coming into the meter.
From what I can
see, there aren't any capacitors or semiconductors interfering.
The oven thermostat has a thermocouple wired to it which for some
reason is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either
the oven element switch, the broil element switch, or both. Then
there is the thermocouple wire which is wrapped(?) internally
around the rotating control
that selects the oven temperature. I don't usually open oven
thermostats so
I'm not sure what exactly is going on inside because once you open
the thermostat,
there is a spring inside the device which displaces everything. In
any case, at room
temperature, there is a connection from L1 to the bake and broil
terminals so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first
plugged the oven into my Sencore PR57 isolation transformer. The
transformer can only supply about 300 watts but I was more
interested in measuring leakage current. No surprise when the low
side leakage to the metal frame measured full deflection even with
the power off to the oven. Not exactly the best situation. The
high side leakage was zero. I turned up the voltage slowly and
the current seemed to rise proportionately to the 17 ohm load
until I stopped at about 300 watts. I should mention that the
heating element did not seem to get warm. Also, the heating
element impedance matched the load across the power plug so that
seemed like a good sign. Then I plugged it directly into the
wall outlet via the Kill-A-Watt
meter. I
turned on the oven switch and an instant trip of the circuit
breaker at the
sub panel occurred. So where is all this extra current coming from
to cook the ground plug on my Kill-A-Watt and trip the breaker? I
must be missing something very obvious.

Thanks for your reply.
--
--
David Farber
Los Osos, CA

Wild_Bill wrote:
There is a comment included in the text on the wiring diagram label,
wrt a bonding strap.

I think you already know, but the earth ground should only have a
path to the exposed metal cabinet parts, and all other parts need to
be electrically isolated from earth ground (the insulating quality of
the isolation needs to exceed the applied/working voltage, hi-pot
being the normal convention).
I believe an 800W element will create a lot of heat inside an
enclosure. I have a 500W 120VAC heater intended to heat engine block
oil pans in winter, and in low light in open air, the deep red color
of the element armor can be seen (not nichrome or resistance wire).



Here's the way I see it. Starting from L1, current flows through the
limit switch then to the thermostat. If the thermostat switch is
turned on by the thermocouple, then the current continues on to the
bake element and then the circuit is completed when it connects to
L2, which is where the neutral line is. I don't see any connection to
that and the metal cabinet parts. So either my analysis is wrong or
there is current leaking to ground.
Just so there is no confusion, from left to right in the schematic,
the original 240V wiring of L1, N, L2 has been changed to 120V wiring
of, Line, Ground, and N. I can remove the bonding strap which
connects the chassis to N in the 240V schematic or Ground in the 120V
version that I came up with. I'd just like to understand what's going
on here.
Thanks for your reply.

Ok so I removed the bake and broil heating elements. I measured each
element's resistance from one end of the element to its metal supporting
plate. And that's where the funky resistance measurements are happening.
There must be some partial internal short from the hot wire inside the
element to the outside supporting tubing. I can't imagine that the
resistance between the two would be less than 1M ohm. The readings were
counting down to as low as 20K ohms. On the other hand, it sure seems
unlikely that both elements would have exactly the same fault. Anyone have a
heating element that they'd like to check the insulating resistance for
comparison?

Thanks for your reply.
--
David Farber
Los Osos, CA

David Farber wrote:

David Farber wrote:

"David Farber" wrote in message
...

This Whirlpool electric stove, model number RF0100, appears to be
an older model. If you were wondering what blasted the ground lead
of my Kill-A-Watt
meter which I posted about two days ago in the thread about the
Phillips security screw, this is the culprit. The schematic is
he
http://members.dslextreme.com/users/...tric-stove.jpg
as I photographed it from the back of the stove.

I used to have the stove hooked up to a 240 volt circuit as
indicated in the
schematic and it worked ok. But, now I don't have a 240V line. Or
at least not yet. I was trying to at least get it to work on 120V
because only the oven will be used and at very low heat, probably
around 200 degrees to cook
some ceramics. The stovetop and broiler wires have been
disconnected because
they are not needed. This particular model does not have a light
or a clock
as shown in the schematic. I wired it so that L1 went to hot
(black), L2 went to N (white), and N to ground (green). The load
across the electric plug, hot to neutral, with the oven switch on,
is 17 ohms. That makes sense
to me. However the impedance reading from neutral to ground makes
no sense to me. I've tried two different dvm's and they both give
bizarre results. When starting at the 2M ohm range, the meter
starts at about 700k and counts
down to about 300k and holds there. When I move the switch over to
the 20M ohm range, the meter starts at about 2.3M ohm and counts
up. The other meter
which is a portable meter counts backward too and then the minus
sign appears on the meter as if current is coming into the meter.
From what I can
see, there aren't any capacitors or semiconductors interfering.
The oven thermostat has a thermocouple wired to it which for some
reason is not shown
in the schematic. I opened the thermostat and found an interesting
mechanical coupling that moves a slider bar that depresses either
the oven element switch, the broil element switch, or both. Then
there is the thermocouple wire which is wrapped(?) internally
around the rotating control
that selects the oven temperature. I don't usually open oven
thermostats so
I'm not sure what exactly is going on inside because once you open
the thermostat,
there is a spring inside the device which displaces everything. In
any case, at room
temperature, there is a connection from L1 to the bake and broil
terminals so I know
it's sending power through to those elements.

Not trusting anything about these electrical readings, I first
plugged the oven into my Sencore PR57 isolation transformer. The
transformer can only supply about 300 watts but I was more
interested in measuring leakage current. No surprise when the low
side leakage to the metal frame measured full deflection even with
the power off to the oven. Not exactly the best situation. The
high side leakage was zero. I turned up the voltage slowly and
the current seemed to rise proportionately to the 17 ohm load
until I stopped at about 300 watts. I should mention that the
heating element did not seem to get warm. Also, the heating
element impedance matched the load across the power plug so that
seemed like a good sign. Then I plugged it directly into the
wall outlet via the Kill-A-Watt
meter. I
turned on the oven switch and an instant trip of the circuit
breaker at the
sub panel occurred. So where is all this extra current coming from
to cook the ground plug on my Kill-A-Watt and trip the breaker? I
must be missing something very obvious.

Thanks for your reply.
--

--
David Farber
Los Osos, CA

Wild_Bill wrote:

There is a comment included in the text on the wiring diagram label,
wrt a bonding strap.

I think you already know, but the earth ground should only have a
path to the exposed metal cabinet parts, and all other parts need to
be electrically isolated from earth ground (the insulating quality of
the isolation needs to exceed the applied/working voltage, hi-pot
being the normal convention).
I believe an 800W element will create a lot of heat inside an
enclosure. I have a 500W 120VAC heater intended to heat engine block
oil pans in winter, and in low light in open air, the deep red color
of the element armor can be seen (not nichrome or resistance wire).



Here's the way I see it. Starting from L1, current flows through the
limit switch then to the thermostat. If the thermostat switch is
turned on by the thermocouple, then the current continues on to the
bake element and then the circuit is completed when it connects to
L2, which is where the neutral line is. I don't see any connection to
that and the metal cabinet parts. So either my analysis is wrong or
there is current leaking to ground.
Just so there is no confusion, from left to right in the schematic,
the original 240V wiring of L1, N, L2 has been changed to 120V wiring
of, Line, Ground, and N. I can remove the bonding strap which
connects the chassis to N in the 240V schematic or Ground in the 120V
version that I came up with. I'd just like to understand what's going
on here.
Thanks for your reply.


Ok so I removed the bake and broil heating elements. I measured each
element's resistance from one end of the element to its metal supporting
plate. And that's where the funky resistance measurements are happening.
There must be some partial internal short from the hot wire inside the
element to the outside supporting tubing. I can't imagine that the
resistance between the two would be less than 1M ohm. The readings were
counting down to as low as 20K ohms. On the other hand, it sure seems
unlikely that both elements would have exactly the same fault. Anyone have a
heating element that they'd like to check the insulating resistance for
comparison?

Thanks for your reply.
You have bad heaters... they shouldn't be below 1M of IR..

If they are connected to together in some way, it's possible one
shorted, causing the other to get over voltage...

Just a theory.. but sounds plausible...

Some food may have splashed on the heaters and cause an internal
thermo warp.. Like something cold hitting them..

old stuff snipped



Ok so I removed the bake and broil heating elements. I measured each
element's resistance from one end of the element to its metal
supporting plate. And that's where the funky resistance measurements
are happening. There must be some partial internal short from the
hot wire inside the element to the outside supporting tubing. I
can't imagine that the resistance between the two would be less than
1M ohm. The readings were counting down to as low as 20K ohms. On
the other hand, it sure seems unlikely that both elements would have
exactly the same fault. Anyone have a heating element that they'd
like to check the insulating resistance for comparison?

Thanks for your reply.
You have bad heaters... they shouldn't be below 1M of IR..

If they are connected to together in some way, it's possible one
shorted, causing the other to get over voltage...

Just a theory.. but sounds plausible...

Some food may have splashed on the heaters and cause an internal
thermo warp.. Like something cold hitting them..

Are these heating elements pretty much standard or do I have to get an exact
replacement?

Thanks for your reply.

--
David Farber
Los Osos, CA

On 10/23/2010 1:21 PM David Farber spake thus:

Are these heating elements pretty much standard or do I have to get an exact
replacement?

My go-to place for such appliance parts is Reliable Parts:
http://reliableparts.com, (877) 733-9241. They're well-stocked and the
people there are knowledgable. I'm going to guess that they'll have
replacements available.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

I should've been paying more attention when I read the part about you using
the PR57 leakage test.
I wasn't picturing/visualizing that the armor sheaths of the heating
elements could or would be in direct electrical contact with the oven
cabinet. I'd been assuming that insulators were in place to isolate them.

I suspect that if the element were removed and the leakage test was applied
to the element, the meter would confirm internal leakage in the element, and
possibly other leakage paths in one or more of the other elements.

The Sencore Zmeters have leakage tests (up to 1kV), as do numerous other
instruments.

Leakage testing can be utilized for many types of electrical and electronic
devices, from full appliances, motors, and other large components, to
transformers and small semiconductor devices.
Megohm meters and Hi-Pot testing equipment/instruments are typically used
for line voltage operated machines, appliances and power transformers for
safety requirements, but also for troubleshooting.

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


"David Farber" wrote in message
...

Here's the way I see it. Starting from L1, current flows through the limit
switch then to the thermostat. If the thermostat switch is turned on by
the thermocouple, then the current continues on to the bake element and
then the circuit is completed when it connects to L2, which is where the
neutral line is. I don't see any connection to that and the metal cabinet
parts. So either my analysis is wrong or there is current leaking to
ground.

Just so there is no confusion, from left to right in the schematic, the
original 240V wiring of L1, N, L2 has been changed to 120V wiring of,
Line, Ground, and N. I can remove the bonding strap which connects the
chassis to N in the 240V schematic or Ground in the 120V version that I
came up with. I'd just like to understand what's going on here.

Thanks for your reply.
--
David Farber
Los Osos, CA