Pipe size for vent in over the cooktop microwave - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 09-12-2019, 06:05 PM Thread Starter
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Pipe size for vent in over the cooktop microwave

I have a microwave that’s mounted over the cooktop. It has a built in range hood that can be ducted to the outside. I need to avoid a stud to get the vent outside, so I’ll have to convert from the 3-1/4 X 10 outlet to round pipe and make a 90 to go through the wall. The directions for the microwave say to convert from 3-1/4 x 10 to 6” round.

I have a really nice 5” vent that’s left over from a Jenn Air downdraft cooktop that I’d like to use so I can make smaller holes in the wall and take up less space in the cabinet above. The total run is probably less than a foot. It’s basically up a couple of inches from the top of the microwave, a left turn, then out through the wall.

Is going from 3-1/4 x 10 to 5” round too much reduction given the shortness of the run?
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post #2 of 7 Old 09-12-2019, 06:35 PM
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Quote:
Originally Posted by Quickstep View Post
Is going from 3-1/4 x 10 to 5 round too much reduction given the shortness of the run?
The 3 1/4 x 10 gives you 32.5 square inches per, while the 5" round gives you
19.625 square inches per. That seems like a pretty significant reduction. And the elbow may have some impact too.

Of course, many people don't or can't vent them at all-the air is just "recirculated" through a charcoal filter.

Jim

"I've learned the hard way that I can't afford to buy cheap tools"
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post #3 of 7 Old 09-13-2019, 08:35 AM
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Charcoal filter bad. Vent good. I have charcoal because of contractor error.



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post #4 of 7 Old 09-13-2019, 08:52 AM
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My cooker hood vented to the kitchen and had no filter at all. It did have a grease grid and I cut a sheet of filter cloth to fit over this.
Microwave sits on kitchen work top and cannot see a vent.
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post #5 of 7 Old 09-13-2019, 01:19 PM
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Probably depends on the kind of cooking you do and how much air you have to vent. You will just have a less efficient system, if you rarely need to use the fan because you don't fry a lot of greasy food, good, on the other hand if it is used frequently on high and you catch a lot of oil then you want maximum capacity. In some cultures a Sakura brand is pretty well a necessity.

Wise men speak because they have something to say; fools because they have to say something -Plato

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Last edited by FrankC; 09-13-2019 at 01:22 PM.
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post #6 of 7 Old 09-13-2019, 01:57 PM
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True, I have my deep fryer in an outside kitchen.
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post #7 of 7 Old 09-13-2019, 03:18 PM
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you could wye to two 5"...
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