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Randall Nortman Randall Nortman is offline
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Default Microwave throwing breaker

On 2008-01-01, Edwin Pawlowski > wrote:
>
> This is normal and acceptable. When a motor starts, (and the microwave has
> one for the turntable) the draw can easily be 2x or 3x the running draw as
> specified. I don't know if the magnetron has a draw like that, but it may
> spike at startup. Circuit breakers are built to take that.


This I know, but the way I heard the story, it is not on startup that
it spikes, but rather gets up to >16A during ongoing operation. I'm
not sure how brief these spikes are. If they're 1/10 second, it
should be fine, but if it's above 15A for more than a second or so, I
think there's something wrong with the microwave. They're long enough
to show up on the meter the repair guy brought, and seem to happen
quite frequently. The breaker usually trips after the microwave has
been running for several minutes, not due to a spike when it first
turns on.


> If an appliance is rated at 14.8A, it MUST be on a 20A breaker according to
> electrical codes. If should be upgraded to 20A and with 12 gauge wire. A
> 15A breaker can take 80% or 12A for a constant load. Sorry, but that's the
> way it is and a new unit will do the same thing.


That makes sense, and whomever installed the microwave probably should
have checked on that. For that matter, the person who sold it to them
should have pointed it out. I certainly hope they have 12ga cable
installed, or else it's going to be an expensive fix. But none of
that changes the fact that the microwave should not be drawing >16A
for more than a fraction of a second, right? 80% of 20A is 16A. If
the microwave draws >16A for extended periods, then even a 20A breaker
might trip (seems unlikely, though). I wish I knew how long the
spikes last and how frequent they are.

Thanks for the info.

--
Randall