Weird Microwave problem - trips breaker when you shut the door!

S

Spudz

Jan 1, 1970
0
We are finsihing up a new construction home, and have a Viking
Microwave on a 20 amp circuit in the kitchen. This is the only device
on the circuit. The microwave cooks fine, but sometimes just closing
the door on the microwave trips the breaker! I have moved the oven to
another outlet and it doesn't trip other breakers. ANy ideas what
might be happeing? I can't imagine closing the door would draw a lot
of current! We have used other devices on the same outlet with no
problems.
thanks!
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M

Mark

Jan 1, 1970
0
Spudz said:
We are finsihing up a new construction home, and have a Viking
Microwave on a 20 amp circuit in the kitchen. This is the only device
on the circuit. The microwave cooks fine, but sometimes just closing
the door on the microwave trips the breaker! I have moved the oven to
another outlet and it doesn't trip other breakers. ANy ideas what
might be happeing? I can't imagine closing the door would draw a lot
of current! We have used other devices on the same outlet with no
problems.
thanks!
To reply via email remove spamnot

is it a GFI breaker?

there is probably an intermittent short in the oven i.e. a wire with
cut insulation or something

Mark

N

nvic

Jan 1, 1970
0
Spudz, sounds like the door is misaligned. When the door is misaligned,
the interlocks switches in the holes where the "hooks" on the door go
don't activate in the right sequence and the circuits breaker trips or
the microwave's internal fuse blows. This, surprisingly, is actually a
feature. It is existant to prevent you from operating it with a damaged
or misaligned door so you don't expose yourself to potentially harmful
levels of microwaves.

Have the door check and, if needed, realigned professionally. Unless
you have the skills and tools to test for uWave leaks (which I highly
doubt), don't fix it yourself. The repair FAQ website has info on the
interlocks and about microwave doors if you DO want to try to fix it.

The URL for the Repair FAQ on microwaves is:
http://repairfaq.ece.drexel.edu/sam/micfaq.htm

N

nvic

Jan 1, 1970
0
Spudz, sounds like the door is misaligned. When the door is misaligned,

the interlocks switches in the holes where the "hooks" on the door go
don't activate in the right sequence and the circuits breaker trips or
the microwave's internal fuse blows. I have seen this happen. This,
surprisingly, is actually a
feature. It is existant to prevent you from operating it with a damaged

or misaligned door so you don't expose yourself to potentially harmful
levels of microwaves.

Have the door check and, if needed, realigned professionally. Unless
you have the skills and tools to test for uWave leaks (which I highly
doubt), don't fix it yourself. The repair FAQ website has info on the
interlocks and about microwave doors if you DO want to try to fix it.

The URL for the Repair FAQ on microwaves is:
http://repairfaq.ece.drexel.ed­u/sam/micfaq.htm

S

Spudz

Jan 1, 1970
0
Well that's interesting - so if the door is misaligned, the oven
shorts the AC line to ground and forces the circuit breaker to blow?
That's bizarre!
Spudz

Spudz, sounds like the door is misaligned. When the door is misaligned,

the interlocks switches in the holes where the "hooks" on the door go
don't activate in the right sequence and the circuits breaker trips or
the microwave's internal fuse blows. I have seen this happen. This,
surprisingly, is actually a
feature. It is existant to prevent you from operating it with a damaged

or misaligned door so you don't expose yourself to potentially harmful
levels of microwaves.

Have the door check and, if needed, realigned professionally. Unless
you have the skills and tools to test for uWave leaks (which I highly
doubt), don't fix it yourself. The repair FAQ website has info on the
interlocks and about microwave doors if you DO want to try to fix it.

The URL for the Repair FAQ on microwaves is:
http://repairfaq.ece.drexel.ed­u/sam/micfaq.htm

To reply via email remove spamnot

R

Ron(UK)

Jan 1, 1970
0
Spudz said:
Well that's interesting - so if the door is misaligned, the oven
shorts the AC line to ground and forces the circuit breaker to blow?
That's bizarre!
Spudz

Via a low ohm high wattage resistor, it doesnt just short out the mains
with an almighty Kerbanggg!

Ron

S

Spudz

Jan 1, 1970
0
Okay well I'll have the unit checked - years of buying cheap
microwaves, never had a problem - we buy a high-end unit and the thing
is having problems right out of the box. Go figure.
THanks, spudz

Via a low ohm high wattage resistor, it doesnt just short out the mains
with an almighty Kerbanggg!

Ron

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S

Sam Goldwasser

Jan 1, 1970
0
Ron(UK) said:
Via a low ohm high wattage resistor, it doesnt just short out the
mains with an almighty Kerbanggg!

Actually, it does. Because, that situation should never occur unless
there is a major problem.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
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Note: These links are hopefully temporary until we can sort out the excessive
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Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
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D

darren

Jan 1, 1970
0
odd that it is tripping the 20A breaker before it blows the 15A
internal fuse though, unless the internal fuse is 20 A. I have also
seen bad breakers before, tripping at a lower rating than they are
supposed to be, but they have all been old. But if the microwave is
not tripping on other outlets, this may be something you want to look
into

N

NSM

Jan 1, 1970
0
odd that it is tripping the 20A breaker before it blows the 15A
internal fuse though, unless the internal fuse is 20 A. I have also
seen bad breakers before, tripping at a lower rating than they are
supposed to be, but they have all been old. But if the microwave is
not tripping on other outlets, this may be something you want to look
into

If you plotted current vs. time for the fuse, the breaker and the microwave
you'd probably figure it out but at this point ....

N

N

nvic

Jan 1, 1970
0
to ron: The one i took apart with same problem and dying mag did.
switch across main, hot to neutral. see Sam GoldWasser's post.

A

Asimov

Jan 1, 1970
0
"Spudz" bravely wrote to "All" (28 Jun 05 11:37:05)
--- on the heady topic of "Weird Microwave problem - trips breaker when you
shut the door!"

Sp> From: Spudz <[email protected]>
Sp> Xref: aeinews sci.electronics.repair:51789

Sp> We are finsihing up a new construction home, and have a Viking
Sp> Microwave on a 20 amp circuit in the kitchen. This is the only device
Sp> on the circuit. The microwave cooks fine, but sometimes just closing
Sp> the door on the microwave trips the breaker! I have moved the oven to
Sp> another outlet and it doesn't trip other breakers. ANy ideas what
Sp> might be happeing? I can't imagine closing the door would draw a lot
Sp> of current! We have used other devices on the same outlet with no
Sp> problems.
Sp> thanks!

I saw this very thing last year. Turned out one of the contacts on the
electric meter was burning up. Your problem is not likely to be the
same but coincidences happen. Perhaps instead the microwave has a door
interlock problem. These are designed to trip the breaker, for safety.
Is it pretty new?

A*s*i*m*o*v

.... On an electrician's truck: Let Us Remove Your Shorts

J

James Sweet

Jan 1, 1970
0
Ron(UK) said:
Via a low ohm high wattage resistor, it doesnt just short out the mains
with an almighty Kerbanggg!

It does on the microwaves I've worked on, the secondary interlock switch
shorts directly across the line and blows the fuse, of course this is never
supposed to happen in actual operation, but is a last resort to prevent
exposure to high power microwave energy should the primary interlock stick.

R

Ron(UK)

Jan 1, 1970
0
nvic said:
to ron: The one i took apart with same problem and dying mag did.
switch across main, hot to neutral. see Sam GoldWasser's post.
That must be the US way then, in over 15 years of repairing microwave
ovens* here in the UK I can't recall seeing one without the
resistor.(Sometimes it looks like a slowblow fuse, with what looks like
a spring inside) It should still blow the internal fuse first unless the
mains breaker is unusually sensitive

cheaper to buy a new oven than to have a fuse replaced

Ron

J

JustMe

Jan 1, 1970
0
Spudz said:
We are finsihing up a new construction home, and have a Viking
Microwave on a 20 amp circuit in the kitchen. This is the only device
on the circuit. The microwave cooks fine, but sometimes just closing
the door on the microwave trips the breaker! I have moved the oven to
another outlet and it doesn't trip other breakers. ANy ideas what
might be happeing? I can't imagine closing the door would draw a lot
of current! We have used other devices on the same outlet with no
problems.
thanks!
To reply via email remove spamnot

A couple of additional possibilities. Note that some circuit breakers will
pop before a slo-blo fuse in the same line. Think door switches and read on.

Food material can gather at the operating pip of any of the door micro
switches. This can be as small as a very light smear of something sticky.
The effect is to slow down the operating speed of one or more switches. This
will cause an intermittent door switch timing overlap when either opening or
closing the door. The actual switch sequence, the switch affected by food
debris, and the particular design of the oven will cause a variety of
different scenarios. THIS IS A COMMON FAULT. You may need a 10X jewellers
loupe to see some food smears which are fully capable of causing a switch to
hang long enough to blow a fuse or trip a breaker.

Another fairly common cause for a switch to hang and disrupt the interlock
sequence is much harder to detect and has a greater capacity to have you
re-working ovens at your expense. This primarily affects the switch in the
sequence that acts as the crowbar, but can also affect even clean
primary/secondary switches after some years use.
If an oven has had a history of one or more fuses blown without a fault
being discovered, the crowbar switch will have had some serious energy fed
into its shorted contacts. This ALWAYS leaves a roughened area on the
contacts. Roughened contacts do not slide as easily as pristine ones and the
slowed-down switch is now likely to blow a fuse intermittently, ***even if
the cause for the original fault is found and corrected.***

Best practise, is to ALWAYS, if possible, examine with a loupe the contact
area of crowbar door switches. Trust no door switches that have switched
full current through them to blow the main fuse. If you have a customer oven
or two that blow switches every week or so, suspect food debris and/or
roughened contacts.

In my experience, most door switch problems with microwave ovens are caused
by (sometimes) tiny amounts of food. I used to buy, and use, 5000
microswitches every 6 weeks or so for this very reason. You cannot
effectively clean food debris off switches. Always put new switches into
clean housings. To do otherwise is to risk doing the job again ***at your
expense***

S

Spudz

Jan 1, 1970
0
Yes its brand new - we just took it back to the dealer yesterday and
they said they can fix/adjust it. We moved the ven to another outlet
(20 A) and it did the same thing... eventually it must have blown the
internal fuse in the oven cuz now it won;t even power up any more.
Thanks again for the advice... I wll never look at a microwave oven
door the same again!

J

Jim Potter

Jan 1, 1970
0
Spudz said:
We are finsihing up a new construction home, and have a Viking
Microwave on a 20 amp circuit in the kitchen. This is the only device
on the circuit. The microwave cooks fine, but sometimes just closing
the door on the microwave trips the breaker! I have moved the oven to
another outlet and it doesn't trip other breakers. ANy ideas what
might be happeing? I can't imagine closing the door would draw a lot
of current! We have used other devices on the same outlet with no
problems.
thanks!
To reply via email remove spamnot

When the door closes there are multiple interlocks. These are set up to
short the ac line and blow the internal fuse if you try to defeat just
one interlock. If there were a brief transient short when you close the
door it could trip a magnetic breaker before blowing the internal fuse.
The fact that it is a problem on one circuit and not another may have to
do with the senitivity of the braker which may vary from breaker to
breaker. If you are qualified to do work in your breaker box (DO NOT IF
YOU AREN"T SURE WHAT YOU ARE DOING!!) you might simply swap the breaker
from the circuit that works to the circuit that's sensitive. Or, you
could get an electrician to do it.

That's the only way I can see a connection with closing the microwave
door unless there is faulting wiring in the outlet that is jarred when
you close the door. If that is the case you could possibley get the same
effect thumping on the countertop or wall.

Good luck.

Jim

N

nvic

Jan 1, 1970
0
Why not jsut plug the uWave into another circuit and unplug everything
else on the circuit. if it trips, it can't be a over-sensitive breaker.

T

Travis Evans

Jan 1, 1970
0
James said:
It does on the microwaves I've worked on, the secondary interlock
switch shorts directly across the line and blows the fuse, of course
this is never supposed to happen in actual operation, but is a last
resort to prevent exposure to high power microwave energy should the
primary interlock stick.

Since virtually all microwaves now seem to be run by electronics, I
wonder why they don't just program the CPU to detect interlock failures
and go into an error condition and refuse to operate, instead of
shorting the AC line? That would sound a lot safer to me. Then again,
I'm not an expert, so maybe I'm missing something.

N

NSM

Jan 1, 1970
0
Since virtually all microwaves now seem to be run by electronics, I
wonder why they don't just program the CPU to detect interlock failures
and go into an error condition and refuse to operate, instead of
shorting the AC line? That would sound a lot safer to me. Then again,
I'm not an expert, so maybe I'm missing something.

What if the main control (triac, relay) which feeds the magnetron shorts
out?

N

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