To recap for the scientists: What size fuse to use in a 22V microwave:

In alt.home.repair, on Thu, 28 Mar 2019 19:07:29 -0500, Dean Hoffman
wrote:

On 3/28/19 7:00 PM, wrote:


12a

Okay. I'll look for 12 amps, I'm glad I asked.
But I may have to settle for 10.


Yep - the problem that caused the 12 amp to blow
has surely cleared itself up by now - so a 10 amp is perfect !
.. or not. John T.

I suspect that was tongue in cheek. If not, fuses fail just
like everything else involving humans. I've changed a lot of them over the years
without having to do anything else.

LOL. I wasn't living here when it broke; I don't know what they did to
it.

By the same token, I'm leaving and I wanted to either put in the right
fuse or leave a note inside the case for the new owner (my roommate
already bought a replacement and they plan to put this one in the lobby
for someone to take.)

The second store I called had it, even 12 amps, not just 10, but as I
expected, only fast-blow. The original was ceramic.

I thought all ceramic fuses were slo-blo, but this one is embossed
F12H250 and some webpages say that F means fast-blow????
"The types of fuses include long-time-lag or super-time-lag (TT),
fast-acting fuses (FF), quick-blow fuses (F) and slow-blow or time-lag
fuses (T)"
https://www.hunker.com/13418825/diff...ic-glass-fuses

Nothing I read decribes why a microwave should need ceramic or slow-blo
(in the power part, not the high voltage part).

One page says " Glass has a low rupturing point, such as 15 amperes."

That's fine since it's a 12 amp fuse, and the normal usage is about 7
amps.

" If a high voltage comes down the electrical line, the fuse element
will melt.

Are there really surges that come down the line that increase the
amperage for normally 7 to over 12?

"The tiny glass fuses are great for small items that don't draw a heavy
amount of current and blow on a regular basis. They don't perform well
outdoors and can shatter when placed in high temperatures due to its low
thermal stability."

Microwave is not used outdoors or at high temperatures.


From before
According to the label on the back "The input is 1400 watts, but it's a
220 volt device, so that's less than 7amps normally. So, 10, right?
Unless F12 in F12H250 at the top means 12 amps? " And the home.repair
people told me it did, but the web says F means fast-blow.

It's a Crystal, model wp900AP23, but no schematic could I find on the
web and the one taped inside just shows fuse, no details.