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OTR vent down and to outside wall?

| Posted in General Discussion on March 28, 2009 11:49am

Hi,

I am looking to install an over the range OTR microwave in my kitchen on an interior wall. The basement ceiling is open so I was hoping to vent it down through the wall and under the floor to the outside wall.

I think in order to do this I’d just 3+1/4 x 10″ rectangular vent in the wall and then and elbow and transition to 6″ round.

The installation instructions for the OTR do not mention this as a viable installation technique in terms of going down and then out. Is there any issue with installing the vent this way?

Thank you,

learner

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Replies

  1. User avater
    Ted W. | Mar 29, 2009 01:04am | #1

    That just doesn't seem right, venting downward like that.

    What's above the kitchen?

     

    ~ Ted W ~

    Tool Auctions - MyToolbox.net
    See my work - TedsCarpentry.com

  2. User avater
    rjw | Mar 29, 2009 01:12am | #2

    There are downdraft vents for some stoves, but I suspect they have stronger fans.

    In planning remember that each 90 turn = 5 feet of vent.


    "Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."

    Howard Thurman

    1. DanH | Mar 29, 2009 04:17am | #3

      And I'd guess, as a quick thumb suck, you should count each foot down as two feet.
      The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith

  3. oops | Mar 29, 2009 05:11am | #4

    I don't think the air cares if it is blowing up or down. If it has been heated a little, I suppose  it would be a little lighter. The length & size of the duct and the number & type of turns would have more of an effect.

    What does the instructions say as to the recommended maximum effective duct length. My guess is if you do not exceed them, you will be OK.

    Have you checked with the Mfr.?  (Not a HVAC pro. just been around a while)

    1. User avater
      rjw | Mar 29, 2009 10:02pm | #10

      >>I don't think the air cares if it is blowing up or down. If it has been heated a little, I suppose it would be a little lighter.Depending on stove use, that air could possibly as hot as a gas water heater flue temp - which isn't much BUT which dos require a fair sized an to move even horizontally

      "Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."

      Howard Thurman

  4. User avater
    Jeff_Clarke | Mar 29, 2009 07:09am | #5

    Is this a combination microwave/hood?  If so I highly recommend that you reconsider - these units are subject to overheating and other problems from this type of installation.

    I know these units are better today than they used to be (for instance - http://www.repair.whirlpool.com/MWR/index.htm and http://www.cpsc.gov/cpscpub/prerel/prhtml07/07562.html and http://log-homes.thefuntimesguide.com/2007/12/ge_profile_microwave_oven_reca.php) but they are typically just OK as a microwave and poor as hoods/vents.

    And, you must follow the manufacturer's instructions (in many states it's a code requirement) especially the distance above the range top.

    Jeff



    Edited 3/29/2009 12:19 am ET by Jeff_Clarke

    1. Learner | Mar 29, 2009 07:36am | #6

      I took a look at an OTR installation manual - couldn't find the model installation manual I am planning on buying online - and it didn't say anything about going downwards. It mentioned pass through wall venting and roof venting but that's about it and the 3+1/4 to 6" elbow adapters.It did have an effective length of venting which was quite high 100 or 140 feet or something. I'd need two elbows to vent down and to the outside which are each considered about 15 effective feet then another 10 horizontally and 5 downwards so I don't think effective feet of vent is an issue.The ceiling above I could vent it through but then I'd have to open up that ceiling and push the vent through and then open up above the sink on the exterior wall in the bulkhead and then core through the brick 15' off the ground outside. Alternatively if I can do the basement venting then I just cut into the wall I am already cutting into for electrical run the vent down and the joists in the basement are exposed. The brick cutting still has to be done but I can be on the ground to do it.This is a combo microwave fan hood - cheap homedepot one - Magic Chef. Thanks for all the replies !

      1. User avater
        EricPaulson | Mar 29, 2009 04:19pm | #7

        What you are reading is the recommended intallation procedures.

        That's whay is does not include directions for venting downward.

        Can you go up and through a joist bay?

        Mount the microwave up in your garage or something and assemle all the ductwork much as you would if you were to down draft it as you propose. Might give you some idea better if it is a viable alternative. Couple, few hours........... 

    2. Learner | Mar 29, 2009 09:16pm | #8

      Thanks for those links. Name a product and you can probably find a recall for a model of that product. I know even circuit breaker panels and circuit breakers have had recall notices. I am not sure that taking this to the extreme and not buying any product where a model of a product has had a recall isn't taking things a little too far. Is there something in general which makes OTR microwaves more susceptible to causing fires than say an on the counter microwave?Thanks again,learner

      1. DanH | Mar 29, 2009 09:36pm | #9

        The main problem with OTR microwaves is that they are a compromise. The unit must be kept smaller than ideal, the fan is going to be less powerful/effective than would otherwise be the case, and the microwave is higher than it's comfortable for many to reach. Plus you pay a premium for all these "features".
        The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith

      2. User avater
        Jeff_Clarke | Mar 29, 2009 11:58pm | #11

        Read the experiences of other homeowners:http://www.consumeraffairs.com/homeowners/magic_chef.html

        Hoods belong over rangetops, but not microwaves.

        Jeff

        1. Learner | Mar 30, 2009 01:56am | #12

          Thanks. That is a good site. I've had an OTR microwave over my electric range for 14 years and I've never had a problem with the unit. This one isn't a magic chef I think it is a GE.The magic chef reports seem concerning especially the random turning on and off. Hard to pay the $1000 for the GE unit when the magic chef is a 1/4 of the price. I still like the idea of the OTR microwave but you might have convinced me to shell out a little more for a better quality unit. I'll have to check the consumer complaints on the other models.

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