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Author: Randall NortmanRandall Nortman Date: Jan 1, 2008 07:01
My parents recently bought a new over-range Maytag microwave, and it's
throwing the breaker occasionally. They told me they had somebody out
to look at it (still under warranty), and he measured the current
going over 16A occasionally. It's a 15A breaker, so no surprise that
it's tripping. But I looked at the sticker on the microwave and it
specifies 120V, 14.8A. Given that, I think that the microwave should
not be drawing >16A long enough to even measure on his meter. I guess
some very brief spikes would be OK, but apparently he was repeatedly
measuring currents over 15A during normal operation. (Unfortunately,
I didn't actually see it; I'm relying on my mother's telling of the
story, and I didn't bring my own meter with me.)
The repair guy said this was normal and told them to upgrade the
breaker to 20A. I say an appliance rated at 14.8A should draw no
more, and if it does, it is defective and should be replaced. Anybody
who knows more about this than I care to comment? Should they demand
a new unit? It was installed just a few weeks ago.
TIA,
--
Randall
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Author: Edwin PawlowskiEdwin Pawlowski Date: Jan 1, 2008 08:18
"Randall Nortman" wonderclown.com> wrote in message
news:13nklf37rd8lred@corp.supernews.com...> My parents recently bought a new over-range Maytag microwave, and it's
> throwing the breaker occasionally. They told me they had somebody out
> to look at it (still under warranty), and he measured the current
> going over 16A occasionally. It's a 15A breaker, so no surprise that
> it's tripping. But I looked at the sticker on the microwave and it
> specifies 120V, 14.8A. Given that, I think that the microwave should
> not be drawing >16A long enough to even measure on his meter. I guess
> some very brief spikes would be OK, but apparently he was repeatedly
> measuring currents over 15A during normal operation. (Unfortunately,
> I didn't actually see it; I'm relying on my mother's...
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Author: Randall NortmanRandall Nortman Date: Jan 1, 2008 09:47
On 2008-01-01, Edwin Pawlowski snet.net> 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.
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Author: Peter APeter A Date: Jan 1, 2008 11:16
> On 2008-01-01, Edwin Pawlowski snet.net> 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...
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Author: Edwin PawlowskiEdwin Pawlowski Date: Jan 1, 2008 11:22
"Randall Nortman" wonderclown.com> wrote in message>
> But none of
> that changes the fact that the microwave should not be drawing >16A
> for more than a fraction of a second, right?
The formula is: Watts
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Author: Peter APeter A Date: Jan 2, 2008 08:06
In article nlpi069.nbdc.sbc.com>, esp@snet.net
says...>
> "Randall Nortman" wonderclown.com> wrote in message>>
>> But none of
>> that changes the fact that the microwave should not be drawing >16A
>> for more than a fraction of a second, right?
>
> The formula is: Watts ÷ Volts = Amps
> Assuming 1780 Watts, a perfect 120 volts = 14.83A That may be true in
> perfect conditions as tested in the laboratory. The electric company is
> allowed to vary the voltage and it may be a bit higher or lower at times,
> especially during heavy use in the summer.
> So, given the same 1780 Watts, we can have:
> 1780 ÷ 110 = 16.18 Amps. This is within the normal and acceptable range. I
> doubt you'd have trouble with a 20A breaker and that is why the code
> requires a safety factor.
>
> ...
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Author: Randall NortmanRandall Nortman Date: Jan 2, 2008 09:01
On 2008-01-02, Peter A CRAPnc.rr.com> wrote:> In article nlpi069.nbdc.sbc.com>, esp@snet.net
> says...>>
>> "Randall Nortman" wonderclown.com> wrote in message>>>
>>> But none of
>>> that changes the fact that the microwave should not be drawing >16A
>>> for more than a fraction of a second, right?
>>
>> The formula is: Watts ÷ Volts = Amps
>> Assuming 1780 Watts, a perfect 120 volts = 14.83A That may be true in
>> perfect conditions as tested in the laboratory. The electric company is
>> allowed to vary the voltage and it may be a bit higher or lower at times,
>> especially during heavy use in the summer.
>> So, given the same 1780 Watts, we can have:
>> 1780 ÷ 110 = 16.18 Amps. This is within the normal and acceptable range. I
>> doubt you'd have trouble with a 20A breaker and that is why the code
>> requires a safety factor.
>> ...
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