Whirlpool electric stove, model RF0100, trips the breaker.

[David Farber]

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



I used to have it 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. Once you open the thermostat,
there is a spring inside the device which displaces everything outside the
container. 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]

Please disregard this post and reply to the newer post labeled, "Whirlpool
RF0100 electric stove trips breaker." My news server was down and I have
since slightly revised my original message.

Thanks.