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-   -   Range Hood Ducting go Down? (http://www.diychatroom.com/f80/range-hood-ducting-go-down-117644/)

jerryk1234 09-18-2011 09:36 PM

Range Hood Ducting go Down?
 
Background: I bought a house. It was a foreclosure. Former owners removed a lot of stuff, including ALL the appliances. Cooktop, range hood,
wall oven, microwave, dishwasher, trash compactor, HVAC....

For the most part, we are reinstalling the same make and level of appliances - Frigidaire Professional. One exception is the range hood. We have invested in a monster Kobe.

The Kobe sticks out 25" - pretty much the entire width of the cooktop.
I would REALLY like it to be high enough so I can lean over the stove without hitting my head. So, standing in front of the stovetop position , I perched a bubble level on top of my head, touched it to the cabinetry, and marked the spot with a piece of masking tape.

The Kobe is 18 inches tall. It's top comes out covering half of the exhaust duct in the wall. So something has to give. Moving the duct is not acceptable. The exterior stucco is virgin, beautiful - and not to be messed with. The current duct system is approximately 5 inches long - just a straight shot right through the wall.

My current idea is as follows: install a piece of rectangular duct in the wall between the studs, with two holes in its sides. One hole connects to the existing round duct to the outside world - shortened and modified with a Dremel. The other hole goes to a second round duct that pokes out through the sheetrock... magically about 6 inches higher than the original hole.

Comments? One thing that worries me: can the ducting for a range hood go *down*? Anybody have a better idea?
Thanks,

- JerryK

Just Bill 09-19-2011 07:37 AM

There are downdraft ranges, JennAir is a big one. The range has a motor in is that blows down. Assuming you have an overhead system, down is probably not the way to go. Thru the ceiling joist bays and out an exterior wall of if an attic above, out the roof.

oh'mike 09-19-2011 07:55 AM

I think you could do that successfully ---the zig zag bend might constrict the flow --and trap grease.

Give us the CFM out put of the fan--the opening size of the old vent---an HVAC person here might be able to figure the flow for you---Mike---

jerryk1234 09-19-2011 11:39 AM

1 Attachment(s)
Quote:

Originally Posted by oh'mike (Post 731265)
I think you could do that successfully ---the zig zag bend might constrict the flow --and trap grease.

*** Grease. I hadn't thought of that. I'll have to put a removable cover
on the duct so grease can be cleaned.
Quote:

Originally Posted by oh'mike (Post 731265)
Give us the CFM out put of the fan

*** It's a Kobe CH03. Speeds are 400CFM, 600CFM,800CFM, and 1000CFM. The CH03 has a duct connection for an 8" round duct.

The installation originally had a Broan Microtek System IV,
which flowed 360CFM. The Broan had a duct connection for a rectangular
3 1/4 by 10" duct. The duct connection in the wall is a 6" round duct.

The cooktop is a Frigidaire Professional 36 gas unit with a total heating capacity of 50,500 BTUH.

Clearly, the design intent for the Kobe was to have an 8" round system. Applying the simple math, we get a cross section of 50 square inches. Our 6" duct outlet has a cross section of only 28 square inches.
A section of 3 1/4 * 10 rectangular duct will have a cross section of 32.5
square inches.

I think I'll get away with it because
* The system is very short. Basically just from the Kobe out through the exterior wall.
* We will probably mostly use the lowest setting. I'm a great fan of quiet in the kitchen.

OTOH, the zigzag *will* produce turbulence inside the duct. Turbulence means noise. I will attempt to mitigate this by
* getting a curved transition piece for the upper end of the rectangular duct. I don't think there's enough space in the wall for a curved transition for the lower end.

* Possibly wrapping the duct with sound insulation. I have some Dynamat left over from an auto project.

Clearly, just moving the duct outlet would make the most sense. HOWEVER, my wife has a purely emotional response to the idea. "No Way, Ain't Gonna Happen, Don't Do it!" ( Yes, dear....) Not to mention
that we wound up with this particular hood because it works with a full-width duct cover, making it so we didn't have to move the hole....

I have attached a picture of the existing situation

Ron6519 09-21-2011 11:23 AM

I think you're bastardizing the installation of this fan. You're using the wrong size duct in a convoluted way. There's no way you'll get the rated exhaust this way.
Pull out the old duct and install the correct size duct in the correct place.
I don't understand about moving the wrong size duct being "not acceptable".
Just the opposite seems to be the case.

jerryk1234 09-21-2011 12:12 PM

Quote:

Originally Posted by Ron6519 (Post 732963)
I think you're bastardizing the installation of this fan. You're using the wrong size duct in a convoluted way. There's no way you'll get the rated exhaust this way.
Pull out the old duct and install the correct size duct in the correct place.
I don't understand about moving the wrong size duct being "not acceptable".

*** It's purely an emotional response from my wife. She does not want to even hear about cutting that stucco. Personally, nothing would please me more than to just cut an 8" hole in the right place, and pop in a direct 8 inch steel elbow duct going from A to B.

I'll be pulling a permit for this later this week. Maybe the building inspector will say "Hell no, I won't let you do that". Then it won't be my fault :).

That being said, just how does one cut an 8" hole in a stucco wall? For 6", it's easy, you just use one of those RemGrit hole saws. $30 and apparently cuts it like butter. But they don't come any bigger than 6".

- JerryK

Ron6519 09-21-2011 02:23 PM

[quote=jerryk1234;733001That being said, just how does one cut an 8" hole in a stucco wall? For 6", it's easy, you just use one of those RemGrit hole saws. $30 and apparently cuts it like butter. But they don't come any bigger than 6".- JerryK[/quote]
Is this old school stucco or the synthetic stucco over foamboard? I guess in either case you could use a grinder for the masonry and a jigsaw for the wood. Don't be surprised if you hit a stud. Open the interior first to check for wires, pipes, etc. before you commit to the exterior hole.
You might need to install a small header if a stud needs to be cut.

jerryk1234 09-21-2011 05:39 PM

Quote:

Originally Posted by Ron6519 (Post 733101)
Is this old school stucco or the synthetic stucco over foamboard? I guess in either case you could use a grinder for the masonry and a jigsaw for the wood. Don't be surprised if you hit a stud. Open the interior first to check for wires, pipes, etc. before you commit to the exterior hole.
You might need to install a small header if a stud needs to be cut.

*** I'll definitely open the interior first - doesn't even have to be pretty, it'll be covered by the new range hood. Measure for the exact spot and verify with a 1/4" hole.
As for what kind of stucco it is - we'll see. The house was built in 2008. Some of the stucco extrusions and decorations do feel a little "hollow" when you tap on them.

The house is an odd mixture of luxury and parsimony. I have never seen so much granite and marble. Even the laundry room is floored in stone. Every bathroom is a work of art. The wooden flooring in the front room is real, and about 1/2 inch thick. But the baseboards are MDF, and the blinds are "faux" wood. ( AKA plastic ). And the HVAC systems were strictly "builder grade".

If it does turn out to be synthetic stucco, what will that mean for my project?

- JerryK

Ron6519 09-21-2011 06:21 PM

[quote=jerryk1234;733203
If it does turn out to be synthetic stucco, what will that mean for my project? JerryK[/quote]
A much easier job.
Traditional stucco jobs were done up to the 1950's around here. Big in the '20's and '30's.

jerryk1234 09-21-2011 06:59 PM

Quote:

Originally Posted by Ron6519 (Post 733241)
A much easier job.
Traditional stucco jobs were done up to the 1950's around here. Big in the '20's and '30's.

*** Hmm. I just read a bit about EIFS ( aka synthetic stucco ) and I have to say that I am not getting warm fuzzies.

- JerryK

Ron6519 09-21-2011 07:09 PM

Quote:

Originally Posted by jerryk1234 (Post 733258)
*** Hmm. I just read a bit about EIFS ( aka synthetic stucco ) and I have to say that I am not getting warm fuzzies.

- JerryK

Then you definitely won't want to read about the class action suits about the first generation EIFS's. Talk about a learning curve with this product.

jerryk1234 09-22-2011 07:57 PM

I was out at the house today. Slightly confused about this EIFS thing.
I *think* that the stucco is the good old traditional kind. HOWEVER, there are some decorations at the front of the house that are definitely some kind of thin pebbly stuff over foam board.

People wrote about the EIFS being relatively soft, and having to be careful around it with ladders & tools. The stuff on this house is really hard - like a rock. No give when you push on it. Can't dig into it with a knife. So I think it's real stucco. Whew.

- JerryK

Leah Frances 09-22-2011 08:16 PM

In many states if it is EIFS they would have had to disclose at the time of sale.

Tell your wife that she will be MUCH happier doing the project right the first time rather than doing a jerry rigged job. Heck, if she's not willing to listen to reason.... regardless of what the inspector says just say that 'he said I have to cut a new hole'.

Trust me, as a wife doing DIY, half my job is managing my husband's whims and expectations. This may or may not be done with occasional deception. EG. my sweet husband thinks he picked the colors for our library.... he picked something awful. So, I picked something similar and have let him think that it's the colors he selected. :whistling2:

jerryk1234 09-22-2011 10:37 PM

Quote:

Originally Posted by Leah Frances (Post 734075)
In many states if it is EIFS they would have had to disclose at the time of sale.

*** It was a foreclosure. The contract said "AS IS" every other page.

Quote:

Originally Posted by Leah Frances (Post 734075)
EG. my sweet husband thinks he picked the colors for our library.... he picked something awful. So, I picked something similar and have let him think that it's the colors he selected. :whistling2:

*** I would *never* try to second guess or fool my wife on colors. She is *extremely* competent in that area. In fact, she's a sort of a professional. She is a paint chemist. I can give her a scrap of sheetrock, and she'll come home with a can of matching paint.

I have talked her into the new duct.

- JerryK

Snav 09-22-2011 10:59 PM

Well thank heavens for that, Jerry.

As another wife who does DIY - never EVER let your spouses mood or desires alter what you HAVE to do. . .you have to put your foot down, sometimes - commence work while they're gone if necessary - and get things done RIGHT. She can put on her big girl panties when necessary, I'm sure.

I've had to make deals with my husband - "you can pick out the kitchen-wall color if I get to rerun all the electrical wiring" and so on. Works for us.


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