Do you have a local appliance store with them hooked up? We have a place locally (SF Bay area) that does and the unit with the inline silencer was fantastic. Unfortunately my application precluded its use. I have approx 4 feet of straight pipe before going through the roof to a 1200 cfm blower. (Abbaka liner, Broan blower) The good news is even with the blower being that close, it is reasonably quiet and much quieter than the vent a hood we have in our primary house. I would love to try a silencer though so I would go that route. The length of your runs sounds fine and 1400 cfm is more than enough. If you have a newer house (tight construction) you may need to look into make up air.

Yes to elbow and silencer.

Yes to 10" duct. But 8" is good too.

Yes also to smaller CFM if you choose to install something smaller. From 700 to 1400 is a doubling. Anything greater than 700 is still good. No need to get into micromanaging the CFM. Just don't up the inline CFM ante on account of yes votes to silencers. Some people have 350 CFM and do fine. Realize that 700 is double that. (Some people have 200 CFM.) Really high end companies like Gaggenau and Miele will sell you things as large as 650 CFM or even 700. There may be a clue here. German companies are known for overengineering things and getting them just right. Going higher than 700 is fine, too. Going higher and higher makes me think that future generations will look back and talk about the overdimensioning that went on back in the day... Or maybe this won't happen. Just a thought, not a campaign. I've never seen one that big. Maybe I'm wrong. Besides, you're in socal so you have the air for free.

Der Hessians don't make 23K BTU residential gas burners.

Indeed there is a *lot* of hot air around here in socal.

It's not the makers of the gas burners setting the cfm stakes but the blower-manufacturers. In fact I'm pretty sure Abbaka's beautiful, bazoingers-big (and expensive), quiet external blowers are German. I think fantech is US-ian, though I'm not sure why I think that....

Miele nor Gaggenau make powerful gas burners therefore they don't offer hoods with high cfm blowers.

Bluestar and Capital offers 1200cfm internal blowers.

Appliance companies build hoods/blowers with their ranges/cooktops in mind.

I will look into that Abbaka.

My guess is that if they are German they were not built with residential kitchen hoods in mind.

Accordin to Dvorsons,an Abbaka dealer, "Abbaka ventilator motors are from Germany and the ventilators are assembled in the USA."

I would bet my guess is correct. The motors originally had another purpose.

Here is a link that might be useful: Dvorsons

Actually, as I had initially wondered, it seems the company is Danish.

Whatever....

Though I suppose it's possible that it is a German compnay that manufactures the blowers for the Danish Abbaka...

But I don't really think this is going to get my kitchen built any faster.... I am tired of noodles. I want some stirfried vegetables!

Here is a link that might be useful: ABBA...

re: that dull roar...

Will an inline silencer mitigate sounds both up and downstream? There must be sound that pulsates outward from the motor that wouldn't be affected by the inline silencer, right?

That is, if the inline motor is as noisy as claimed on another concurrent thread and verified by specs, will the silencer only mitigate kitchen noise and not roof (or neighbor's) noise?

Actually, the Danish Abbaka builds the high power blowers/ventilators in the USA because that is where there is a demand/need.

Abbaka hoods are made in Denark.

Will an inline silencer mitigate sounds both up and downstream? There must be sound that pulsates outward from the motor that wouldn't be affected by the inline silencer, right?

That is, if the inline motor is as noisy as claimed on another concurrent thread and verified by specs, will the silencer only mitigate kitchen noise and not roof (or neighbor's) noise?

With an inline blower the silencer is usually placed between the blower and hood mitigating sound to the kitchen.

If you want to mitigate sound outside you would need a silencer between the blower and the roof.

That would be a rather long run!

Der Hessians don't make 23K BTU residential gas burners.

Pillog,

Dat iz der funny.

Now correct me if I'm wrong (I'm sure you will), but I remember reading that if you have two motors, say 1200 instead of 600 in a Prestige blower, you will get somewhat more motor noise but not nearly twice as much. You will get significantly more noise at the higher reaches of your motors but it is mostly the air rushing through the baffles, not the motor. Also seem to remember being told that you had to put the inline motor at some distance away from the hood to significantly decrease the noise. Which we could not feasibly do.

I cannot remember all the twists and turns of the logic but I came out of the maze feeling that internal (for my particular setup) would make the most sense and having the 1200 CFM would be worthwhile -- a relatively small cost upgrade considering the overall project, and could run the unit at lower speed most of the time but still have the turbo standing by for stir fry. And we did a 10 inch duct.

My new hood is Modern-Aire 1200 that is two 600's. I don't remember who makes the blowers. It's internal--vents straight out the wall so no dislocating it. My previous hood was Modern-Aire 600, vented out a different wall, same kitchen. The new hood on lowest (no idea what speed that is), is quieter than the the old one at full speed. The new one at full speed is loud, but not so much that one needs to shout over it. Barely.

I use it on lowest for a lot of tasks. If I'm thinking about what I'm doing on something complicated, with my head bent over my pan, or with the hood turned up into the mid-range, I don't hear the door. There's a fancy knocker and an intercom button. The chime for the latter is enough to serve as a doorbell, even though it rings upstairs, except when I'm zoned out under the hood. Then I jump out of my skin when people let themselves in. :) Most of the time, if I'm alone in the house, it's the UPS man I'm missing. Mind you, this is lost in thought, browning individual pieces of meat and turning them and all, and I could put in a proper doorbell.

If I'm doing something long and involved and sitting in the kitchen, the hood noise does get wearing. I'm talking counting into hours. But I'll take the noise over the noisome (i.e., smells). Mostly, it doesn't bother me, unless I'm specifically looking for quiet.

Pillog, thanks for your post. Thats good news. We don't have our hood yet but was hoping it would be as you say for the 1200.

BTW I think EBM Pabst makes the Modernaire internal motors.

Very helpful practical experience, plllog & sayde. Thanks (as always).

Sayde, I'm sure Kas will chime in with a correction... but I would think from what he's said, that basically, "overhead", if you will, is noise-insulation cfm-wise. Meaning... 1 motor with 800cfm max run at 800cfm will be louder than one motor run with 1200cfm max run at 800cfm -- he had an explanation having to do with rotation vibration I think? Sorry, Kas; gotta dump some loading on the grey-matter with all that's going on, and the why-specifics didn't make the cut though the bottom-line did.

So ... thinking through on translating to 2 motors, I'd think it would generally be the other way around. OTOH I think the specifics of the fans themselves might be most important of all rather than trying to generalize.

Here's what Kas said on this subject:

Dominant fan noises would include motor noise from vibration and blade tip turbulence. I don't think generalizations about one fan at some speed versus another fan at a different speed should be accepted as canonical truth. Usually running a fan slower will make that fan less noisy although this requires a well behaved fan curve with no positive slopes for all rpm.

Typically, a manufacturer will design so that the fan on maximum produces some tolerable level of noise for its application and cost point. Hence a 1200 cfm rated fan at full speed will normally make more noise than a 1500 cfm rated fan running at a speed where it would pull 1200 cfm at zero static pressure. However, if these fans are manufactured by different sources with different opinions of how much noise is too much, it is not certain that the larger rated fan will be quieter at the lower flow rate. I would hazard that if the larger rated cfm fan is also physically larger, it will likely be quieter at the lower flow rate. All of this ignores many variables including the variation in blower construction.

All of which leaves me thinking I should actually chase down some dB curves and compare the fans themselves. Kaismom's experience was seriously disturbing. Here's what she says:

We put in Fantech 8 inch 409cfm external mounted fan on our outside wall. It works well enough for getting the grease and steam out of our 4 burner range. We will not be keeping it because we cannot run it beyond 1/3 max of the capacity.

The problem is the noise. The fan is mounted outside wall of our kitchen, and it is too noisy for us and our neighbors. We flunked the noise ordinance of the city at max level of the fan. When turned on at max, it sounds like an airplane taking off.

The noise issue was really important to us. We called the company to see if we can get some noise data. They simply reassured us that it was 'quiet' but would not give us a specific noise level. We 'trusted' the company thinking how noisy could a fan really be... (shame on us!) Guess what, we were really wrong on that trust and assumption. It produces about 80dB of noise at max at the property line which is about 5 ft from the fan, which is WAY too noisy in a neighborhood with close neighbors. The noise ordinance states 55dB at the property line. Not only that it is so noisy, we really cannot use it at the max level inside the house either. I suppose if the fan was 20 ft or more away from the kitchen AND it was far far from the neighbor, then the noise would not have mattered. That is NOT the situation for us.

Don't bother with this fan. You get what you pay for. The reason that this is cheap is probably because they did not put 'quietness' into the cost of engineering and manufacturing.

Following what she wrote I looked at those dB curves and they *did* say 80dB at full speed. And that's just 409cfm.

It seems using the silencer is very effective in one direction, but not the other. I'm thinking now the best thing to do is maximize passive capture area (size of hood) and fudge on getting a lower cfm fan. It'll be cheaper and quieter (and less MUA problems, though this isn't probably an issue for us). But I probably need to investigate the manufacturer as well. sigh. When will this all end? I am SO sorry we ever started this remodel, I cannot tell you...

plllog's observation of newer and older MA experience is consistent with the fan itself mattering. I'm guessing MA changed fan manufacturer at some point between old and new (but maybe the ventilation configuration was responsible).

Yes to ".... the best thing to do is maximize passive capture area (size of hood)..."

1. build an aquarium shape upside down. End of story. Done.

No to : "... But I probably need to investigate the manufacturer as well. sigh. ..."

2. put an inline fan above it in the duct. End of story. Done.

3. add filter. End of story. Done.

hth

Ding dong [chime sound, not a comment on anyone's personality]

Most of us who are using high flow rate blowers with in-line noise attenuation have moved the noise to the outside, usually high up on the house roof where it is less obtrusive. Also, we may live where house to property line distances are significantly larger than 5 ft. I haven't measured it, but the noise at five feet from my Wolf/Broan 1500 cfm rated roof fan at its highest speed surely exceeds 80 dB.

As my text quoted by aliris19 above hints, noises emanating from a blower typically increase with rpm. A larger slower device will be quieter. Compare the compact blowers used with hoods to a Casablanca type ceiling fan, which can easily move as much air with much less noise.

If I were constrained by house configuration and noise and distance ordinances, and had to have high flow, I would investigate large, well-balanced, low tip velocity options, and might have to go to a commercial source for advice and product. An example of such a source would be Greenheck. And the product I would expect that I might need would be something like an upblast fan deliberately operated at reduced speed. (Commercial upblast exhaust fans often use belt drives between motor and fan, and can be configured by pulley (sheave) diameters to yield different fan speeds for given motor speeds.)

kas

On the new vs. old Modern-Aire hood, there were only about 7-8 years between. They might have been the exact same fans. One in the old one, two in the new one. Running the old one on the lowest setting was nearly useless. I mostly ran it on high, sometimes middle. Running the two fans together on lowest almost always useful, louder for sure than the one, but I don't think it's as loud as the old one on highest, maybe the same as middle, might be the same combined flow as middle, no clue if so. :)