GFCI trips on a separate circuit

[[email protected]]

Sometimes my microwave trips the other circuit that has our computers
on it, even though the appliance is on a different circuit at the far
end of the house. This happens maybe 1 out of 3 starts.

I've replaced the GFCI and it still trips; moved the microwave to a
third different circuit - same problem.

The microwave has been working normally for almost 5 years, but has
recently started making a buzzing sound on start up.

 

[Bob Shuman]

If they are truly on separate circuits then what you describe is happening
should not be possible. Perhaps the circuits have a common (improperly
terminated) neutral wire and the devices are floating and are seeing
transients during start up?

Bob

 

[Jerry G.]

The microwave oven should be operated on its own circuit breaker from
the panel. It is best to use a standard type circuit breaker for a
microwave oven, because of its characteristics.


Jerry G.

 

[bz]

[email protected] wrote in [email protected]:

Sometimes my microwave trips the other circuit that has our computers
on it, even though the appliance is on a different circuit at the far
end of the house. This happens maybe 1 out of 3 starts.

I've replaced the GFCI and it still trips; moved the microwave to a
third different circuit - same problem.

A GFCI trips when it senses that the current on the hot and return lines
are not the same [implying leakage to earth somewhere] or when there is a
significant voltage sensed on the safety ground.

Look for any way that currents flowing in the microwave's power circuit
could be getting to the GFCI for your computers.

The microwave has been working normally for almost 5 years, but has
recently started making a buzzing sound on start up.

Probably unrelated to your GFCI problem.





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[dodger741]

The microwave has been working normally for almost 5 years, but has
recently started making a buzzing sound on start up.

Sounds like your microwave is the culprit and ready to die. GFCI
circuits must be fairly sensitive to sense small inbalances in current
in their respective circuit. If the microwave is injecting
significant EMI back into your house circuit, no telling what could
happen. You could test this theory if you have some sort of emi
filter you could plug the microwave into between the outlet and oven.
I don't know if a surge protector power strip provides any sort of emi
filtering or if it just protects against over voltage spikes.

 

[hr(bob) [email protected]]

Sounds like your microwave is the culprit and ready to die.  GFCI
circuits must be fairly sensitive to sense small inbalances in current
in their respective circuit.  If the microwave is injecting
significant EMI back into your house circuit, no telling what could
happen.  You could test this theory if you have some sort of emi
filter you could plug the microwave into between the outlet and oven.
I don't know if a surge protector power strip provides any sort of emi
filtering or if it just protects against over voltage spikes.

You could borrow a neighbors microwave for an hour and put it on the
circuit where your microwave trips the GFI. If both microwaves trip
the GFI, you have a problem unrelated to the microwave and probably
some sort of leakage on the other circuit that makes it more sensitive
to the minor surges that the microwave causes when it switches.

 

[Paul]

I have a little mini-tesla coil for checking out high vaccuum stuff.
It generates a huge amount of EMI. It will set off any GFCI that is on
it's circuit, even though the device is 2-wire. Naturally the spark
goes to ground, and would trip a GFCI. Perhaps your microwave has a
high voltage breakdown and that's what is causing the circuit to trip.
Does it do this more on humid days?

-Paul

 

[w_tom]

Because important details are missing, then different answers are
provided; all correct because each is based upon different
assumptions.

Bob Shuman's and bz's answers assume a GFCI in the breaker box. As
correctly noted, a GFCI's white neutral wire must remains electrically
separated from all other neutral wires. And both black (hot) and
white (neutral) wires must be keep separate from other circuits so
that even milliamps cannot leak through a partially penetrated wire
insulation.

If GFCI is in the kitchen, then dodger741's answer is relevant.
That assumes the computer is somehow on the same circuit. Not clear
from your post which circuit has the GFCI.

Paul's questions about environment when tripping occurs is also
relevant.

And finally, if the microwave is generating too much common mode
noise, then common mode filtering in a computer (on a GFCI circuit)
could trip that GFCI. But that would have to be a massive common mode
noise generator - would definitively interfere with other radio
frequency equipment (AM radio, TV screen?).

 

[Sam Goldwasser]

Because important details are missing, then different answers are
provided; all correct because each is based upon different
assumptions.

Bob Shuman's and bz's answers assume a GFCI in the breaker box. As
correctly noted, a GFCI's white neutral wire must remains electrically
separated from all other neutral wires. And both black (hot) and
white (neutral) wires must be keep separate from other circuits so
that even milliamps cannot leak through a partially penetrated wire
insulation.

If GFCI is in the kitchen, then dodger741's answer is relevant.
That assumes the computer is somehow on the same circuit. Not clear
from your post which circuit has the GFCI.

Paul's questions about environment when tripping occurs is also
relevant.

And finally, if the microwave is generating too much common mode
noise, then common mode filtering in a computer (on a GFCI circuit)
could trip that GFCI. But that would have to be a massive common mode
noise generator - would definitively interfere with other radio
frequency equipment (AM radio, TV screen?).

It might be worth taking the microwave and trying it on a circuit WITH
a GFCI (preferably, both the computer circuit and another one). It
should not trip.

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