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Anyone installed their range hood higher than recommended?

Posted by deedles (My Page) on
Tue, Feb 26, 13 at 0:33

Has anyone done this and if so, how did it work and did you wish you hadn't or is it okay? Did you get a bigger blower to compensate? Or a wider hood. How much higher did you go?
Trying to not block the view. =/

X post to kitchens, too.

Thanks very much.


Follow-Up Postings:

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RE: Anyone installed their range hood higher than recommended?

We are planning to do this - they are going to install the blower today - hood surround is still being made. We are mounting it at 7' off the floor. It is going over a 30" blue star. Because of the increased height, we went with an oversized blower and hope we won't have to turn it up so high - the Abbaka external 1400, we also went with a custom sized hood - the finished hood will be 40" x 26" Hopefully it works well!


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RE: Anyone installed their range hood higher than recommended?

I'd love to find out how it works for you when it's up and running.

Could you burn something really smokey, too?

:)


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RE: Anyone installed their range hood higher than recommended?

The higher you mount your hood, the larger it needs to be on all 4 sides, since you are using an island hood.


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RE: Anyone installed their range hood higher than recommended?

Wouldn't it need to be bigger even if it wasn't an island type hood? Or is anything I'd put in there be like an island type hood due to the lack of a wall?


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RE: Anyone installed their range hood higher than recommended?

My island hood is 34 inches above the cooktop surface. Size that matters is the internal aperture, which is 27 inches front to back. This is centered over the boundary of the hob diameters. Width is the largest that Wolf supplied at the time, and covers with some overlap both an induction wok hob as well as a 36-inch wide induction cooktop. Fan is nominally 1500 cfm. Actual flow at minimum house negative pressure (i.e., with MUA) should be around 900 cfm due to baffle, transition, and duct losses vs. the fan curve. Capture is nearly complete in most cases.

When the aperture is moved up to seven feet above the floor, a hood is in the commercial installation category, and flow rate per square foot of aperture, as well as overhang beyond the cooktop zone, should also be commensurate with commercial practices. Twenty inches of pan edge overlap on each of the four sides is recommended for island configurations. (More exactly, the angle between the hood aperture edge and the nearest pan edge should be at least 22.5 degrees to vertical.) With a wall backing, and side cabinets, reduction is possible in those directions. The Greenheck reference material at my Clippings can provide more perspective, and the thermal plumes analysis papers more details.

For baffled hoods, aperture area (sq. ft.) times 1.5 ft/s times 60 s/min is the lowest air flow full-power achievable capability that I would recommend. This assumes that the baffles provide an effective factor of two air entrainment velocity enhancement to the impinging effluent. (The effluent rises from the pan at about 3 ft/s.)

kas


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RE: Anyone installed their range hood higher than recommended?

Really, kas, 22.5? Not 22 or 23? Haha just kidding, kas! Thanks for all your help on my kitchen exhaust system about a year ago...

I'm sure you know this already, deedles, but listen to kaseki on all matters related to ventilation, makeup air, etc. He is the man. Not the bad kind you want to stick it to, the good kind you want to high five.


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RE: Anyone installed their range hood higher than recommended?

Thanks davidahn. You are welcome.

The 22.5 was a value within the range reported in the plume studies. It is half of 45 degrees, which is a common enough angle to use to picture the conical effluent plume. (The cone is like an ice cream cone, with an imaginary cone tip located somewhere below the pan.)

kas


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RE: Anyone installed their range hood higher than recommended?

Kas- do you have a photo of your setup?


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RE: Anyone installed their range hood higher than recommended?

Not deliberately, but I can take one. I'll try to get to it tomorrow or Saturday.

kas


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RE: Anyone installed their range hood higher than recommended?

kaseki: your post about all the overhang needed and what not pushed us over the line in our design. We are putting up a wall behind the stove flanked by pass throughs, in order to keep the size of the range hood reasonable in our small kitchen. Thank you for that as it seems to be not only functionally better but aesthetically improved, too!

so, would a 900 cfm external blower for a 36" vent over a vintage stove (9,000btu burners) with a 36" cooking area, installed at 33 to 36" high be good enough? Not perfect, but good enough seeing as how I don't do a lot of high smoke producing cooking?

I'm willing to give up a little to get that hood up a little higher on the wall.


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RE: Anyone installed their range hood higher than recommended?

Ours (42-inch) is installed at 36 inches over a 36-inch range top (BS) and it works fine for us. We do some high-heat Indian cooking and I am impressed at how well it captures. (Tradewind)


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RE: Anyone installed their range hood higher than recommended?

Heh. I find it hard to evaluate good enough when it depends on others olfactory sensibilities. Good enough has to be considered in the context of the triangle: aesthetics, performance, affordability - pick two out of three. I wouldn't spend my life hating my kitchen once I had, with due consideration, picked a design point within the triangle.

Photo still on to-do list.

kas


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RE: Anyone installed their range hood higher than recommended?

GWIolo:

The attached photo taken with a Nikon Coolpix and scaled to 1/4 pixel count in each dimension using Gimp shows the relationship of the two induction units to the hood. The wide angle causes some distortion. Some staging was necessary to reduce clutter.

The unit on the left is the Cooktek 3500W induction wok hob, while the unit on the right is a Kenmore clone of an Electrolux Icon 36-inch cooktop. The primary difference is that the actual E'lux cooktop has an additional metal band between controls and hobs.

Hope this shows whatever aspect you were looking for.

kas


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RE: Anyone installed their range hood higher than recommended?

Kas,

What wood are your cabinets made out of? Lovely!


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RE: Anyone installed their range hood higher than recommended?

I am looking to install my range hood higher then suggested as well so this is perfect timing.. we are trying to maintain balanced pressure in the house so we are installing a fan compensating system for the house.

Kas, what is the mfg of the induction wok. I have been looking for one but no luck finding one for in counter.


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RE: Anyone installed their range hood higher than recommended?

Katy-lou:

Cabinets were fabricated by Tedd Wood. The wood is red birch. It has been semi-matte lacquered to reduce the sparkle look (called chataqua, I think, but I can't confirm the spelling right now). I like the sparkle look but DW wanted it subdued. I was never able to determine whether any other treatment was used in addition by Tedd Wood, but my own testing showed that matte lacquer tends to achieve that effect.

five4me:

The induction Wok is an MWDG-3500 by CookTek Magnawave Systems located in Chicago IL. (www.cooktek.com). Note the separated control panel. Initially I intended to put the panel into the top front of the cabinet, but decided a cutout in the soapstone was a better choice for control while cooking. For retention and sealing of the units, I used a thin slightly double sticky neoprene tape product used in the auto body trade under the edges. I can look up the part number if necessary. The bonding to the soapstone is decent but with some force the units can be removed without damaging anything.

And before anyone asks, the overdue-for-oiling soapstone is Belvedere by Tiexeira, and the granite on the background and unseen foreground peninsulas is Piracema White - Wave by Ripano Stone Works. Black Sillites are installed in the soapstone for outlets.

Also worth noting is that had it existed in the form I wanted, I would have ordered a hood that was even longer to ensure capture and comply with my own assertions, although as it happens capture is pretty good. The real capture problem in the kitchen (and this may be true of most modern kitchens using wall ovens) is escaping effluent from wall ovens when broiling after a door is opened to remove the meat.

The two exhaust registers I mounted in the ceiling above the wall ovens have no capture volume and would have to cover most of the ceiling to be effective against the rolling wave of hot greasy gases pouring out when the door is opened. Ranges will also tend to spill effluent out into the kitchen when their ovens are opened, but being under their cook-top hood, the spill will at least be partially collected. An alternative would be to pan sear and then cook in the oven, or only bake bread in the oven and bask in the fragrance.

kas


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RE: Anyone installed their range hood higher than recommended?

Restaurants use these big, four foot deep hoods that can suck up effluent from ovens, grills, and cooktops alike, but it's interesting that residential oven venting gets so little attention. I have an oven set in the wall to one side of the cooktop, and the 54" hood kind of half-covers it. If I remember to turn the hood on in time. Bread can, in fact, set the smoke detector off. I bake hot.


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RE: Anyone installed their range hood higher than recommended?

Kas,
What model cooktek do you have ? Is your fan1500cfm on low or high?


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RE: Anyone installed their range hood higher than recommended?

Cooktek model number may be found in my message above.

Rated zero static pressure flow rate of the Wolf supplied (but Broan manufactured) fan is 1500 cfm. These values are always specified at rated voltage at full phase power. The Wolf hood provides a continuous diac-triac phase control to reduce fan power to lower values and hence reduce fan cfm as desired. I usually operate the fan at or near high when wok cooking.

I estimate that actual cfm with adequate MUA should be around 900 cfm on high.

kas


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RE: Anyone installed their range hood higher than recommended?

deedles-we're thinking of a 34" to 36" hood placement of a Wolf or Broan hood (182436) due to his height. Have you decided on height yet?

kas-might you explain continuous diac-triac phase control power (fan cfm) a bit more? Is your Wolf fan (Broan supplied) on a variable circuit or an infinite circuit? Or does variable/infinite circuitry not relate to diac-triac fan power.

If you know, could one theoretically wire a new infinite wire Wolf/Broan vent hood with a Universal X10 remote switch to allow control of the new hood by an infinite wall switch? I have a fully working 1000 cfm external blower and wall switch exterior blower control in place,

I had no idea that Wolf external fans are Broan originals. That is important information to know, especially for make up air possibilities and wiring of dampers within Wolf and Broan hoods. Strange no dealer passed this on, as I've been concerned about the two manufacturers interfacing electrically with one another for quite some time. Great information.

Thank you for this thread, deedles.


Here is a link that might be useful: Universal X10 remote switch:

This post was edited by SparklingWater on Thu, Mar 7, 13 at 17:38


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RE: Anyone installed their range hood higher than recommended?

My Wolf fan (purchased at the end of 2007) was made for Wolf by Broan according to Wolf. A few other Wolf fans were also made by Broan as of 2007. I cannot assert anything with respect to other Wolf fans or more modern Wolf fans. Contact Wolf for fan curves for their fans you might be interested in and compare them to Broan fan curves published on their web site.

Basically what one buys when buying a hood and fan from Wolf is the comfort of knowing that compatibility has been established and no electrical hacking is going to be necessary to make a doit yourself scheme function. Wolf could impose additional reliability requirements on Broan, for example, but may not need to; a NuTone upblast roof fan I have used for my kitchen since the '70s is still fully functional today. So at least at one time the NuTone branch of Broan could build reliable devices.

Using a circuit architecture that I am pretty sure GE published in the late 1960's or early 1970's, it is possible to control the amount of power available on a line by excising part of the sinusoidal voltage available. (The circuit actually allows part of the sinusoid.) While I can address the transfer functions and other details of triacs and diacs (once I recheck old literature), the circuitry to support them is pretty simple. This information is probably on line.

These same circuits are used on lighting controls. The main difference between motor controls and similar lighting controls is that motor controls click on to full power, with rotation to lower power, and lighting controls do the opposite.

More complex lighting controls also exist, such as zero-crossing switching, and have advantages in reduced electrical noise. These schemes could also be used for motor control, but are not in the case of my hood.

By continuous I mean the the control rotates smoothly between full power to perhaps 10% power (have not measured this) over about 270-degrees of rotation. Ignoring quantum mechanics and grain boundaries, the resolution of the rotary potentiometer that is used for control is effectively infinite between those limits. The phase angle that turns on power each half cycle is adjusted by the control angle to fall between perhaps 5-degrees (out of 180) to perhaps 160 degrees. Turning on even later in the phase cycle would send power to the motor at too low a level for it to keep running.

Is "infinite" a brand name?

Induction motors of the type used by many fans can ususally be controlled over a reasonable range by phase angle control. They can also be controlled by variable frequency control, but this will be more limited as they are typically permanent capacitor split phase and designed for a single frequency.

The Wolf hood control is mounted in the hood and is wired to the motor on the roof. I have seen its guts and that is why I know it is diac-triac type. Other control locations are possible, including wall controls. In that case a hood that does not contain a fan control would be appropriate.

kas


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RE: Anyone installed their range hood higher than recommended?

Thanks kas. Appreciate your reply. "Infinite wiring/ switch" is as I understand it, is a non-variable fan motor speed (in my case 1000 cfm blower) controlled in my case by a wall switch that alters that 1000 cfm from off position to "high, medium, low". I believe the conduit is hot, neutral, grounded, possibly an older conduit from the newer variable speed motors where you dial in your speed. I am considering using my ext blower and wall switch as it is in place, and obviates the need for new blower and new and long conduit placement (20 feet). I haven't decided yet.

deedles, I'm not trying to highjack your thread, but following up on some of the blower discussion here. I had my 6'2" spouse stand in front of our 24" cooktop as I held up large pot covers at both 30" (too low) and 36" (still a little low but doable) at 24" depth from back. Definitely going to do 36" heigh from counter.

This post was edited by SparklingWater on Fri, Mar 8, 13 at 11:17


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RE: Anyone installed their range hood higher than recommended?

There are motors with different windings that connect to multi-position switches to change speed. The motor controls I was describing just use the hot and neutral circuit to reduce power. Typically they provide variable speed, but it is also possible for them to be designed such that instead of a potentiometer, a three or four position switch is used.

kas


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RE: Anyone installed their range hood higher than recommended?

Good information here, thank you. I have a very tiny kitchen, a new NRX range 30" not installed yet in an island. The island opens to a tiny living area . My ceiling is height is 80" and zip room for hidden ducting. Everything I read about ductless ventilation says it is terrible. Is it possible to find a island hood that is higher to not obstruct view to living area and can use rectangular 3.5 Deep by 10" wide ducting that can run along ceiling to an existing wall vent. I could box it in with wood for a better look. ??? I appreciate your response.


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