Reuben's Home Inspection Blog

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No, Your Range Hood Isn't Broken (It's Installed Wrong)

I’m a big fan of range hoods that exhaust to the exterior, and I like them even more when they’re installed properly, but this doesn’t always happen.  I find a lot of problems with range hoods when I inspect homes, and today I’ll review a few of the most common defects.

Backwards fans.  By far, the most common installation defect that I find with over-the-range microwave / hood fans is a blower fan that’s installed backwards.  Microwave fans are designed to exhaust out the back, exhaust out the top, or recirculate air out the front.  Depending on how the fan is installed, the internal fan needs to be rotated to blow in the proper direction.  The diagram below comes from an installation manual, and helps to illustrate this.  I frequently find fans that are designed to re-circulate the air, or blow it out the front, but when I turn the fan on, it just makes a lot of noise.  No air is coming in or out. The repair for this condition is to un-install the microwave, rotate the internal fan, then re-install the microwave.
Microwave Hood Fan Hood Fan Diagram
San Yang Pai

Too powerful. One of the most powerful fans I’ve seen is a Japanese brand called San Yang Pai. These particular types of kitchen exhaust fans are just too powerful for most homes.  The least powerful fan they make is rated at 650 cubic feet per minute (cfm), which is a ridiculous amount of air being removed from the house.  By comparison, the most powerful residential hood fan made by Whirlpool is rated at 370 cfm.  Every time I’ve inspected a house with a hood fan made by this company, the fan has been so powerful that it caused the water heater to backdraft.  The water heaters always function fine after I turn the hood fan off.   The fix is to replace the fan or have additional make-up air brought in to the home (or just not use the fan, but I never recommend that).
Reduced Duct

Improper duct. The standard for range hood exhausts is a 6″ rigid metal duct.  Anything smaller will always violate the manufacterers installation instructions – as far as I know.  I’ve never seen a manufacturer that allows anything smaller than 6″.   The photo at right was taken at a condo conversion in Minneapolis.  The builder had to replace the duct with the proper size, and I’m sure it wasn’t a fun project.

 

Improper wiring. Most hood fans come with a cord that needs to be plugged in to an outlet, or they have an opening in the cabinet so they can be hardwired.  I see a lot of hood fans in Minneapolis and Saint Paul wired with lamp cords or extension cords, and this is never a proper installation.

Reuben Saltzman, Structure Tech Home Inspections – Email - Home Inspector Saint Paul

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 7 commentsReuben Saltzman • June 30 2009 06:27AM

Comments

Thanks for sharing your post this morning with us. I look forward to more from you. Have a great day!

Posted by Eric Villaverde (DoubleTree Home Inspection Services L.L.C.) about 11 years ago

Reuben at 600cfm a person could blow dry their hair while they cook:)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) about 11 years ago

Reuben, Maybe Japanese cooking requires more air movement. Or the fan doubles to cool thee cook.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 11 years ago

Eric - you too, thanks!

Charles - or the fan could double as a flowbee!  Remember those?

James - yeah, I could see the fan cooling the cook.  I could feel the draft just standing in front of the fan.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 11 years ago

650 CFM!  That's one powerful sucker.  I just don't see the need for that much air moving over the stove!

I've found a few fans wired backward too!  Usually it's just a case of reversing the wires to ensure the fan is rotating in the right direction.

Posted by Erby Crofutt, The Central Kentucky Home Inspector, Lexington KY (B4 U Close Home Inspections&Radon Testing (www.b4uclose.com)) almost 11 years ago

Is there a good, no, great microwave that has a solid, powerful vent that will take out the cooking smell and smoke when I walked above a natural gas cooktop?

Posted by Geoff over 2 years ago

*when installed above a natural as cooktop ?

Posted by Geoff over 2 years ago

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