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Placing objects on top of a microwave oven

Discussion in 'Electronic Basics' started by Ed Masters, Oct 27, 2004.

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  1. Ed Masters

    Ed Masters Guest


    I have a question about microwave ovens which probably sounds a bit
    silly, but here goes...

    Prior to purchasing a small microwave from an online store, I needed
    to check whether it had vents on top of the unit, as in my small
    kitchen it would be on a benchtop and I wanted to use this space for
    resting light objects. I've never actually seen vents on the top of
    any microwave, but the manual was non-specific and suggested there may
    be, so I thought I'd better check. The manufacturer's respresentative,
    who'd just returned from speaking to technical support to get an
    answer to my question about the vent location (they're on the side),
    very strongly warned against placing objects on top. Even small
    objects, I asked, like cooking utensils? "No, no, no way! It might
    blow up".

    Now, I understand these companies have liability issues to worry about
    and will warn against pretty much everything. Common sense tells me
    that placing a teatowel on the top surface (in such a way that it
    doesn't over the edges and cover vents) and resting light objects like
    clean cooking utensils on it should not be a problem, but I'm not up
    to speed on electronics so perhaps there's a technical issue I'm not
    considering. Is any technical reason why I should not place light
    objects on top of a microwave?

  2. Rich Grise

    Rich Grise Guest

    No. It's a sheet metal box, for heaven's sakes. ;-)

    Don't block the vents, or the thermal cutout will make it
    stop cooking till it cools, but as far as microwaves, it's
    an inert box. Grounded, BTW, so you can even put static-
    sensitive utensils on top. ;-)

    Bon Appetit!
  3. ----------
    No, he's as uneducated as you sre, he's just covering his ass.
    Remember him the next time your ignorsnce leads you to cover
    YOUR ass.

  4. Ed Masters

    Ed Masters Guest

    Thanks, Rich. Sounded like it was actually worth asking about (at risk
    of looking like an idiot) after I got off the phone with them, but in
    retrospect it does sound rather silly :)

  5. Ed,

    Vent openings should - off course - never been covered. But a microwave that
    blows things that are placed on top of it is a very dangerous appliance. It
    sure does not fulfil the safety regulations and is not allowed to be sold in
    most countries. So I think that representative did not know where he's
    talking about like most salesmen often do. The only accident I ever met was
    fatal for some pottery placed on top of the microwave. Due to the vibration
    caused by the turntable the pottery walked to the edge and beyond...

    BTW. Microwaves *never* should leak out of the oven. As fat and grease tend
    to conduct microwaves, you have to keep your oven clean. Especially the door
    and posts.

    petrus bitbyter


    The TOP of your microwave oven could be dangerous, but not for the
    reason anyone thinks.

    In some ovens (like mine!), the light bulb that illuminates the
    inside of the oven is very close to the metal top. In normal
    operation this causes little problem. However, if you leave
    the oven door open for many hours, the light stays on, and
    the metal top becomes extremely hot. Plastic bags fuse to the
    paint. Candles turn into pools of liquid wax. I doubt it
    could start a fire, but it certainly could destroy a CDROM left
    up there.
  7. Have you seen the CD inside the oven? Now THAT destroys it.
  8. Can someone explain why we worry about door seals on microwaves leaking,
    when the door has a metal grill that I can see through!

  9. James Beck

    James Beck Guest

    Because the holes are smaller than the 1/4 wave length of the frequency
    in use, so for all intents at the 2.5GHz or so the oven is using the
    grill is a solid piece of metal.
  10. Rich Grise

    Rich Grise Guest

    You might have noticed William J. Beaty's reply. I completely forgot
    about the light bulb, so I was wrong. If the light stays on for a
    long time, the top of the oven will get hot.

  11. I wonder what size of hole would cause problems? In my old oven,
    the 0.25" hole I drilled in the top had no measureable leakage. At the
    same time, there were a few mW/cm^2 at one corner of the door, and the
    door was NOT damaged or even dirty.


    Drill a hole in your oven wall! It lets you reach in with a plastic
    stick and poke at sizzling sample-objects. Or stick an NE2 bulb in
    the end of a soda straw and explore the 3D hotspot pattern.
  12. OH YEAH

    OH YEAH Guest

    Microwaves are by no means - my specialty, so my assumption here could be
    wrong.... But I'm wondering.... the hole on "top" of the microwave maybe
    being "above" the main oven components - was still "shielded" from the
    "active" parts? Where as the door was inline with the deflected microwaves?
    Just a guess.

    As to placing things on top of the oven, I do and have been for a while. No
    big deal as most of my cooking time is less than 10 minutes. Now, if it were
    to be say an hour, I'd probably move the stuff as I have noticed that the
    oven "starts" to get a little warm at the 10 minute mark. And no - the vents
    are not blocked. They're out to the sides and rear. There is sufficient
    space on the sides and rear to allow for it.
  13. Rich Grise

    Rich Grise Guest

    Don't drill a hole in your oven.
    No, actually, it is because up to a certain size, the microwaves don't
    even realize that there's a hole there. It's too small for them to
    get through, just like the holes in the door grille.

    This is also why ants don't cook. ;-)

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