What cooktop or range are you trying to vent? This will help with what type of suggestions are offered. Have you considered an internal blower rather than an external or inline blower? I don't think your installation will be difficult. A 600CFM blower would not need more than an 8" duct. What is the size of the rectangular duct? If you already have an inline blower, it seems like you are just replacing parts and it should not be that difficult!

Good luck!

A company called prestige has both a remote and an in-line blower 1000 cfm that requires 8" duct. Models are RB1000 for the remote and IL1000 for the in-line

to answer homepro01: the size of our rectangular duct is approximately 12 by 5 inches. we have a Bosch gas range about 1.5 years old, one notch below the top of the line, so the hottest burner is a little less hot than in the top of the line. Most of our cooking does not generate a lot of smoke or heat, but about once a week we do stir frying or stovetop grilling that does not get adequately exhausted. That's when the top of the rangehood gets greasy, a dead giveaway that the exhaust is inadequate. We also occasionally have grease leak onto the tile backsplash from the bottom of the rangehood, which is a sign that the stuff is not getting pumped out with sufficient force or maybe we don't wash the mesh filters often enough. We're hoping to correct these problems with a slightly stronger exhaust system. I was thinking that 800 to 1000 cfm would be appropriate, but I was told that anything over 600 requires make up air. I don't want to do that. For me, that's over the top. We take our cooking seriously, but not that seriously. So we're hoping that going from 400 something cfm to 600 (plus the design improvements in the new models) will improve things for us sufficiently to justify the expense.

The size (diameter) of your duct is important.

Separate, independent and unrelated are A.) the shape and size of your collector thingie and B.) the motor-blower-insert-airmover.

The collector umbrella is called a sump: it is a sink but inverted. Think of any sink and its plumbing underneath. The size (diameter) of your plumbing is the important thing, not the brand.

Pairing "X" rangehood with a "Z" remote blower is great. Air doesn't care what sump it is being collected into nor which blower is pulling it through the duct. So, you will encounter no compatibility concerns. Hope this resolves one thing for you.

Measure the duct and find a blower that is designed for it. Call Broan or Nutone, and a couple others.

David

I go with a store that specializes in selling, servicing and installing the rangehood. Vent A Hood franchise comes to mind. If you are not happy; they can in many cases fix the problem. If you do not want to go along with Vent A Hood; then I go and spend a few more dollars and get the firms that install commercial Rangehoods for restaurants to do the work. They are the pros.

I agree with Harry. I've had great experience with Vent-A-Hood Customer Service. They are knowable and patient!

I'm still undecided. I've read several complaints about excessive noise with vent a hood. So I'm reluctant to go with them. We have a small kitchen, so we want as low a noise level as possible. That's why we want a remote blower. But looking at the systems I really want, the cost exceeds what we paid for our range. So we're still thinking.

If noise is an issue, VAH is not your best choice. Remote blowers are in a totally different league when it comes to noise levels.

Higher cfm may or may not compenate for smaller duct, but 8'' is not that unreasonable.

I'm the one (or one of several) with a Modern Aire hood liner and Fantech blower. It's an absolutely killer combination. The only thing about a hood that determines size of duct used is the size of the duct collar. You can always hook the hood to a short run of 10'' and then use a transition to connect to your 8'' run.

fantech has remote blowers for 8'' ducting: check out the FKD 8, rated at 835 cfm I believe. Their blowers are the gold standard for remotes, IMHO.

Depending on where you live, 600 cfm definitely does NOT necessitate makeup air. Unless code requires it, or you live in a VERY tightly sealed house, there will be plenty of air infiltration without dedicated makeup air. At worst, open a window a crack (or in my case, if not in use, I can open the fireplace damper :-)

Check out Modern Aire if you need anything custom. Might cost a bit more, but usually not much more, and you get exactly the specs you want.

Thanks, clinresga. I am studying your suggestions very closely and will seriously consider them. I have recently got interested in the Prestige hood because it is the deepest on the market (I think), so that it completely "covers" the front burners, and it has a deep sump. I am considering pairing it with a Fantech remote, instead of a Prestige fan, because they are less costly and typically are claimed to require a smaller diameter vent. That might mean installing a wall switch if the switch in the rangehood is not compatible with the fan. No big deal, just another complication and slight added cost.

My quandry is that although our present system is not entirely adequate, it has served us reasonably well. And upgrading means paying a lot more for a disproportionately small improvement in performance. And I'm of two minds about the new styling because ours is a really modest eat-in kitchen. Although I've equipped it with quality appliances, it's not flashy or readily recognizable as upscale, which might put it out of keeping with amenities in our house. I still want something better than what we have, but haven't decided how badly I want (need) it. I'm not usually this indecisive. I suppose if I had a rare opportunity to see one of the systems I'm considering in a functioning kitchen and can see how it looks and performs, especially when greasy smoke is billowing from a frying pan, I might decide in an instant.

haus:
I think you are approaching this issue with a very sensible mindset. I have a few more thoughts.

Re the Prestige hood: they have had consistently positive feedback here on GW, although of course I have no personal experience. Can you say exactly which model you are looking at? I honestly don't believe that there are huge design differences between brands, so I agree that what you should be focusing on is first, maximum capture area, and secondarily, the depth of the hood (the "sump depth"), which also has some effect on performance

Reading your earlier posts, is the Prestige designed for 10'' duct? As much as I am a fanatic about ducting (the amount of time and $$ I spent getting my duct transtitioned from 10'' to 18 x 4'' rectangular and back to 10'' again was ridiculous) I don't think your run is all that bad. You go from a 60 sq inch cross section rectangular to a roughly 50 sq in round duct, not as nice as the 75 sq inches you get with 10'', but decent. The upside is that your run is quite short. Even with two turns that is not bad compared to a typical first floor to attic run.

So...even if the Prestige is designed for 10'' duct, I don't think it's unreasonable just to transition it to your existing ductwork. Will it be as good as new 10''? Of course not, but it will be better than what you have if you use a decent blower.

Speaking of that, I love Fantech blowers (we have two, one for the kitchen hood, one in the master bath). The remote mount FKD 8XL is the smaller verion of the FKD 10XL we have, which kicks B###. The 8XL is rated at over 800 cfm at zero inches of pressure, more than adequate to pull through your duct I suspect. Remote mounting is totally superior to internal blowers and would always be the better choice IMHO. You'll get some motor noise if you don't use a silencer, but it will still far outperform an internal sound-wise.

By the way, the requirement for a wall switch is not a disadvantage, it's a huge advantage. I hate craning my neck around to see the switches in our VAH hood at the lake. For the MA, I just reach to the left of the range and boom. AND...you can use an infinitely variable rheostat, giving you complete control over how fast the blower is running, a huge plus.

I think that the Prestige plus an 8LX would be a substantial upgrade over existing. It will likely make you happy (at least until you see what our 64'' MA hood and 10XL blower and LD10 silencer can do :-)

Just to add a bit more confusion, count me among the Vent-a-hood fans. My 600 cfm is not particularly noisy - I can still watch and hear the TV in the next room. My previous kitchen had no ventilation at all, so this is the first time I've ever had to experience any range hood sounds. I wish I had access to to VAH's support - my dealer was pretty clueless and had no recommendations about anything. I don't think I did too badly considering I was pretty much on my own.

Uh oh: cooknsews is triggering an irresistable urge to go on my VAH and noise rant.

So many folks who tout their VAH hoods are like cooksnswes in that they don't have any standard of comparison. In cooks case, this appears to be the first hood he/she has had. I have a bit more experience to rely on, as I too have a 600 cfm VAH at our lake house, as well as our MA hood with Fantech remote blower.

Based on that, I will unequivocally state that the VAH is very noisy when compared to a remote blower installation. I have previously documented this objectively in an earlier post where I actually measured noise levels of my two hoods:

vent hoods and noise: the real scoop

There's no question that when it comes to sound, a remote blower like the Fantech plus their LD10 silencer is far superior to any internal blower.

In addition, I'm unaware of many reports of great customer service from VAH. I can rave about MA's support based on my ongoing interactions with them and particularly with Jeff Herman there. Others have posted similar experiences with Jeff on this Forum.

And finally, this is not to disparage VAH hoods--hey, I own one! It's a solid hood with limitations that are not due to poor design or construction. Rather it's the difference between an off-the-shelf mid range system versus a custom high end take no prisoners system, so it's not a fair head to head comparison (though before buying a VAH you really owe it to yourself to price out a higher end option like the MA, as the price differential may shock you--much less than you might guess!).

I am going to saute about 4 pounds of beef cubes tomorrow for a beef stew. I'll be following all the rules about turning on the blower a few minutes early to get an updraft going, and may even use the rear burner because it is entirely under the hood capture area (while the front burner is only partly under the hood). And I'll try to give our existing 400+ cfm remote blower system an impartial appraisal. This kind of cooking is about the most demanding that we do in terms of the burden on the exhaust system, and we don't do it very often.

If our system flunks this test, I'll know I have to replace it. I'll want one with a remote blower that's compatible with the existing ducting -- that's not negotiable. I'll also want one with a deep sump that covers more of the front burners than the one we have now. It should also be constructed of 304 type stainless steel, not the crumby 430 type. And it should have baffle filters which I understand allow the exhaust system to operate more efficiently than the mesh type.

The Prestige model PL30240 satisfies all these criteria and comes with a 600 cfm internal blower (not acceptable) and a choice of remote blowers. I am considering using a Fantech remote blower of about 800 cfm, if they make one in that range and especially if it is EnergyStar rated.

The PL30240 will cause us to lose the small cabinet above our present hood -- no big deal because it doesn't hold that much. But I worry that all that stainless steel will give a "showstopper look" that will go out of fashion like the avocado appliances of the 70s. Aside from that, I still need to convince myself that all the expense and disruption will be worth it in terms of the improved performance. I'm still struggling with the issue that I may be paying a lot more for just a little bit more. We'll see.

What do you mean I have no standard of comparason? I'm comparing it to ambient kitchen sounds, what you have happening in the total absence of any exhaust system. When it comes down to it, anyone's opinion of the noise in their environment is much more dependant on their qualitative judgement than the reading on any metre.

Anyway, just to put some numbers to my experience, I got out a dig sound metre. Ambient noise levels in my kitchen, at ear level in front of the stove ranged from 50-60 db, depending on whether anyone was talking. My 600cfm VAH on Low recorded about 60 db, on Med 60-62, and 62-64 on High. The readings on my metre were constantly fluctuating but these numbers represent my best guess at average values. I expected higher readings on the High setting, but the sound difference between Med and High was more of a pitch change than overall loudness.

I still don't consider this a loud system.

Didn't meant to suggest that you are unable to make subjective judgments on whether something is noisy or not. I just think it's difficult to benchmark a hood versus other hoods, rather than ambient background, without the ability to hear a different hood in action. If it relates to a decision on what hood to buy, then it's hood to hood comparisons that are most relevant. Hood to ambient comparisons are relevant I guess for a decision of hood vs no hood, which wasn't a consideration for me.

Interesting to hear your SPL meter readings. They are quite different than mine. Curious what weighting you used. If you're getting 62 db with your VAH on high, measured with C weighting and with the meter held at ear level at working distance to the range, then there's a huge difference. I consistently got 65 db at low and 67 at high.

I'm not sure why your meter readings were so variable: at steady state, I saw very little variation in sound level, and could peg the reading down to one db.

Just for comparison again, parrym had posted these levels for her Kobe:
QuietMode - 380cfm, 1.0 sones, 51dB
Low Speed - 560 cfm, 3.0 sones, 66 dB
Medium Speed - 720 cfm, 4.5 sones, 74dB
High Speed - 800 cfm, 4.8 sones, 75 dB.

She too could get a reading to one db range. Again, her readings tend to confirm how loud internal blowers can be, although yours may be an exception.

I'm also not quite sure what "medium" represents on your hood. On my VAH I can run the left fan only, the right fan only, or both together. Since both fans are virtually identical, the Left only and Right only settings are pretty redundant, and I'm surprised there was a significant difference in SPL between them on yours. No difference on mine.

Anyway, perhaps my VAH is unusually loud or yours unusually quiet, in which case consider yourself lucky!

Our metre readings were done at the C setting. Perhaps my variable readings could be attributed to the gaggle of teenagers eating breakfast in the next room. I'll try it again later.

On my VAH, the right blower has two settings, which I call Low & Med. The left one has only one speed, which kicks the whole unit into High.

You are in a unique situation to be able to test multiple vents in real kitchen settings. Most of my family/friends are making do with those wussy little filter fan things over their stoves, but none have high performance ranges. Those of them who cook either raved about VAH or their Jenn-air downdrafts, but I wouldn't consider the latter.

The dealers in town were next to useless, even though I suspect they sell loads of high end stuff. Maybe I'm just sniffing conspiracy, but I think it may be management policy that the floor staff isn't trained in the nuances of kitchen vent technology. If they knew more, they might end up losing a few sales by admitting to customers such as myself that there are HUGE installation costs associated with any system sucking 300cfm or more. In my case, the installation cost 4x the retail price of my VAH. I can't imagine how much more remote blowers, let alone more cfm might have cost.